Signal transmission method and device

Abstract

Provided are a signal transmission method and a device. In the method, a first communication device converts a first radio frequency electrical signal into a unidirectional envelope modulation signal, and sends a first radio frequency optical signal to a second communication device. Wherein, the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by performing optical modulation on the unidirectional envelope modulation signal and having a flat lower envelope and a lower envelope amplitude less than or equal to a first value. A carrier in the unidirectional envelope modulation signal is a sine wave. Moreover, the unidirectional envelope modulation signal is a radio frequency electrical signal with a flat lower envelope, and an upper envelope of the unidirectional envelope modulation signal corresponds to an upper envelope of the first radio frequency electrical signal; or the unidirectional envelope modulation signal is a radio frequency electrical signal with a flat upper envelope, and a lower envelope of the unidirectional envelope modulation signal corresponds to a lower envelope of the first radio frequency electrical signal. According to the manner, transmission optical power between the first communication device and the second communication device can be reduced, and power consumption of the optical device and the nonlinear effect of optical fiber transmission can be reduced.

Description

Signal transmission method and device Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a signal transmission method and device. Background Art

[0002] Future wireless base stations will develop towards multi-band sharing, ultra-large arrays, and ultra-large bandwidth, leading to a dramatic increase in the amount of data required for traditional digital wireless fronthaul. Furthermore, due to the extensive digital-to-analog conversion and data processing required by base stations, base station power consumption will also increase dramatically with this surge in data volume. Combining wireless RF and photonic technologies allows for the generation, transmission, detection, and processing of wireless RF signals, enabling direct optical transmission of wireless RF signals. This reduces the amount of digital-to-analog conversion and analog-to-digital conversion required, simplifies data processing, and ultimately improves transmission efficiency and reduces base station power consumption.

[0003] In the wireless fronthaul downlink, the RF electrical signal can be converted from electrical to optical to generate an RF optical signal. This signal is then transmitted via optical fiber. The RF optical signal is then converted from optical to electrical to generate an RF electrical signal, which is then output to the antenna for radiation. Increasing the transmitted optical power of the RF optical signal can increase the RF radiation power of the antenna. However, higher transmission optical power leads to a sharp increase in the power consumption of optical devices in the link and severe signal distortion caused by severe nonlinear effects in optical fiber transmission.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a signal transmission method and device that can reduce the transmission optical power, which is beneficial to reducing the power consumption of optical devices and the nonlinear effects of optical fiber transmission, and is also beneficial to achieving higher antenna RF radiation power with lower transmission optical power.

[0006] In a first aspect, an embodiment of the present application provides a signal transmission method, which can be applied to a first communication device, a chip in the first communication device, or a logic module or software that can implement all or part of the functions of the first communication device. The following description takes the first communication device as an example. The signal transmission method includes: the first communication device converts a first radio frequency electrical signal into a unidirectional envelope modulation signal; the upper envelope and lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulation signal is a sine wave. The first communication device sends a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating the unidirectional envelope modulation signal, and the lower envelope is flat and the lower envelope amplitude is less than or equal to a first value. The unidirectional envelope modulation signal is an radio frequency electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulation signal corresponds to the upper envelope of the first radio frequency electrical signal; or the unidirectional envelope modulation signal is an radio frequency electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulation signal corresponds to the lower envelope of the first radio frequency electrical signal.

[0007] It can be seen that the flat upper envelope or flat lower envelope of the unidirectional envelope modulated signal is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optically modulating the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper envelope and lower envelope of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulated signal is lower, thereby reducing the transmission optical power between the first communication device and the second communication device, thereby helping to reduce the power consumption of optical devices. In addition, in the scenario where optical fiber is used to transmit optical signals between the first communication device and the second communication device, the reduction in transmission optical power is also conducive to reducing the nonlinear effects of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effects of optical fiber transmission. In the scenario where the second communication device also outputs the first RF electrical signal to the antenna for signal radiation, this signal transmission method is conducive to achieving higher RF radiation power of the antenna with lower transmission optical power.

[0008] In an optional embodiment, the first radio frequency electrical signal is determined based on a baseband signal. The first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulated signal, including: the first communication device determines the unidirectional envelope modulated signal based on the first radio frequency electrical signal and the first electrical signal. The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal.

[0009] In an optional embodiment, the first communication device determines a unidirectional envelope modulation signal based on the first radio frequency electrical signal and the first electrical signal, including: the first communication device superimposes the first electrical signal on the first radio frequency electrical signal to obtain a unidirectional envelope modulation signal. It can be seen that the first communication device can obtain the unidirectional envelope modulation signal by adding or subtracting the baseband amplitude signal from the first radio frequency electrical signal, which is conducive to obtaining a first radio frequency optical signal with low average optical power, thereby reducing the transmission optical power between the first communication device and the second communication device. In addition, the baseband amplitude signal and the first radio frequency electrical signal are separated in the spectrum, and the operation of the first communication device superimposing the first electrical signal on the first radio frequency electrical signal causes little damage to the first radio frequency electrical signal and is easy to implement in the baseband.

[0010] In an optional embodiment, the first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

[0011] In an optional embodiment, the first communication device converts the first radio frequency electrical signal into a one-way envelope modulation signal, including: the first communication device converts the first radio frequency electrical signal into a second radio frequency electrical signal, the second radio frequency electrical signal being a positive half-amplitude signal or a negative half-amplitude signal of the first radio frequency electrical signal relative to a DC component; the first communication device filters the second radio frequency electrical signal to obtain a baseband signal and a baseband signal in the second radio frequency electrical signal; the first communication device adjusts the amplitude of the baseband signal and the baseband signal in the frequency spectrum to obtain a one-way envelope modulation signal. The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal; and the difference between the amplitude of the baseband component and the amplitude of the baseband component in the frequency spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value.

[0012] As can be seen, the first communication device can obtain a unidirectional envelope modulated signal by first converting the first RF electrical signal, which is a full-wave signal, into a second RF electrical signal, which is a half-wave signal, and then performing filtering and spectrum amplitude adjustment on the second RF electrical signal, which is a half-wave signal. This method can be implemented on the RF link and does not include baseband processing, which can reduce the impact of baseband processing on the signal.

[0013] In an optional embodiment, the method further includes: the first communication device superimposing a first bias electrical signal on the unidirectional envelope modulated signal through an optical modulator; and the first communication device optically modulating the unidirectional envelope modulated signal after superimposing the first bias electrical signal through an optical modulator to obtain a first radio frequency optical signal.

[0014] In an optional embodiment, the optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0015] In an optional embodiment, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, and the first bias electrical signal is a first bias voltage signal; the voltage corresponding to the first bias voltage signal is greater than the first voltage. In scenarios where the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, a laser diode can be additionally used to generate the light source, and the electro-absorption modulator or Mach-Zehnder modulator can achieve light modulation based on the light source generated by the laser diode. Thus, light source generation and light modulation are achieved by different devices, which helps reduce the impact of the light source bandwidth on high-frequency modulation when the voltage corresponding to the first bias voltage signal is low.

[0016] In an optional embodiment, the method further includes: the first communication device generating a first radio frequency electrical signal.

[0017] In a second aspect, an embodiment of the present application provides a signal transmission method, which can be applied to a second communication device, a chip in the second communication device, or a logic module or software that can realize all or part of the functions of the second communication device. The following description takes the second communication device as an example. The signal transmission method includes: the second communication device receives a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, and the lower envelope is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulation signal is a sine wave. The second communication device converts the first radio frequency optical signal into a first radio frequency electrical signal; the upper envelope and lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component. The unidirectional envelope modulation signal is an radio frequency electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulation signal corresponds to the upper envelope of the first radio frequency electrical signal; or the unidirectional envelope modulation signal is an radio frequency electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulation signal corresponds to the lower envelope of the first radio frequency electrical signal.

[0018] It can be seen that the flat upper envelope or flat lower envelope of the unidirectional envelope modulated signal is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optically modulating the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper envelope and lower envelope of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulated signal is lower, thereby reducing the transmission optical power between the first communication device and the second communication device, which is conducive to reducing the power consumption of optical devices. In addition, in the scenario where optical fiber is used to transmit optical signals between the first communication device and the second communication device, the reduction of the transmission optical power is also conducive to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission.

[0019] In addition, the second communication device also converts the first RF optical signal with lower average optical power into a first RF electrical signal with higher power. In the scenario where the second communication device also needs to output the first RF electrical signal to the antenna for signal radiation, this signal transmission method can achieve higher RF radiation power of the antenna with lower transmission optical power.

[0020] In an optional implementation, the first radio frequency electrical signal obtained by converting the first radio frequency optical signal is a baseband signal in a unidirectional envelope modulated signal obtained by performing photoelectric conversion on the first radio frequency optical signal.

[0021] In an optional embodiment, the second communication device converts the first RF optical signal into a first RF electrical signal, including: the second communication device performs photoelectric conversion on the first RF optical signal using a photodetector to obtain a unidirectional envelope modulated signal; the passband of the photodetector covers the spectrum of the baseband signal. The second communication device filters the unidirectional envelope modulated signal using a bandpass filter to obtain the first RF electrical signal; the passband of the bandpass filter only contains the spectrum of the baseband signal. It can be seen that the second communication device can restore the first RF optical signal to the first RF electrical signal using the photodetector and the bandpass filter without performing complex algorithmic processing, thereby simplifying the method of restoring the first RF electrical signal.

[0022] In one optional embodiment, the second communication device converts the first RF optical signal into a first RF electrical signal, including: the second communication device performs photoelectric conversion on the first RF optical signal using a photodetector to obtain a unidirectional envelope modulated signal, and determines the first RF electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector only includes the spectrum of the baseband signal. As can be seen, when the photodetector has both the function of photoelectric conversion and the function of filtering out the baseband signal, the second communication device can directly recover the first RF optical signal into the first RF electrical signal using the photodetector, without performing complex algorithmic processing, thereby simplifying the method of recovering the first RF electrical signal.

[0023] On the third aspect, an embodiment of the present application provides a signal transmission method, which is explained from the perspective of the interaction between a first communication device and a second communication device. The method includes: the first communication device converts a first radio frequency electrical signal into a one-way envelope modulation signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the one-way envelope modulation signal is a sine wave. The first communication device sends a first radio frequency optical signal; the first radio frequency optical signal is a one-way envelope radio frequency optical signal obtained by optically modulating the one-way envelope modulation signal, and the lower envelope is flat and the lower envelope amplitude is less than or equal to the first value. The second communication device receives the first radio frequency optical signal. The second communication device converts the first radio frequency optical signal into a first radio frequency electrical signal.

[0024] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0025] It can be seen that the flat upper envelope or flat lower envelope of the unidirectional envelope modulated signal is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optically modulating the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper envelope and lower envelope of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulated signal is lower, thereby reducing the transmission optical power between the first communication device and the second communication device, which is conducive to reducing the power consumption of optical devices. In addition, in the scenario where optical fiber is used to transmit optical signals between the first communication device and the second communication device, the reduction of the transmission optical power is also conducive to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission.

[0026] In addition, the second communication device also converts the first RF optical signal with lower average optical power into a first RF electrical signal with higher power. In the scenario where the second communication device also needs to output the first RF electrical signal to the antenna for signal radiation, this signal transmission method can achieve higher RF radiation power of the antenna with lower transmission optical power.

[0027] In an optional embodiment, the first radio frequency electrical signal is determined based on a baseband signal; and the first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulated signal, including: the first communication device determines the unidirectional envelope modulated signal based on the first radio frequency electrical signal and the first electrical signal. The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal.

[0028] In an optional implementation, the first communication device determines the unidirectional envelope modulation signal based on the first radio frequency electrical signal and the first electrical signal, including: the first communication device superimposes the first electrical signal on the first radio frequency electrical signal to obtain the unidirectional envelope modulation signal.

[0029] In an optional embodiment, the first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

[0030] In an optional embodiment, the first communication device converts the first radio frequency electrical signal into a one-way envelope modulation signal, including: the first communication device converts the first radio frequency electrical signal into a second radio frequency electrical signal, the second radio frequency electrical signal being a positive half-amplitude signal or a negative half-amplitude signal of the first radio frequency electrical signal relative to a DC component. The first communication device filters the second radio frequency electrical signal to obtain a baseband signal and a baseband signal in the second radio frequency electrical signal. The first communication device adjusts the amplitude of the baseband signal and the baseband signal in the frequency spectrum to obtain a one-way envelope modulation signal. The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal; the difference between the amplitude of the baseband component and the amplitude of the baseband component in the frequency spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value.

[0031] In an optional embodiment, the method further includes: the first communication device superimposing a first bias electrical signal on the unidirectional envelope modulated signal via an optical modulator. The first communication device optically modulates the unidirectional envelope modulated signal superimposed with the first bias electrical signal via the optical modulator to obtain a first radio frequency optical signal.

[0032] In an optional embodiment, the optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0033] In an optional implementation, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, and the first bias electrical signal is a first bias voltage signal; the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0034] In an optional embodiment, the method further includes: the first communication device generating a first radio frequency electrical signal.

[0035] In an optional implementation, the first radio frequency electrical signal obtained by the second communication device by converting the first radio frequency optical signal is: a baseband signal in a unidirectional envelope modulated signal obtained by the second communication device performing photoelectric conversion on the first radio frequency optical signal.

[0036] In an optional embodiment, the second communication device converts the first RF optical signal into a first RF electrical signal, including: the second communication device performs photoelectric conversion on the first RF optical signal using a photodetector to obtain a unidirectional envelope modulated signal, wherein the passband of the photodetector covers the spectrum of the baseband signal in the unidirectional envelope modulated signal; and the second communication device filters the unidirectional envelope modulated signal using a bandpass filter to obtain the first RF electrical signal, wherein the passband of the bandpass filter only includes the spectrum of the baseband signal in the unidirectional envelope modulated signal.

[0037] In an optional embodiment, the second communication device converts the first radio frequency optical signal into a first radio frequency electrical signal, including: the second communication device performs photoelectric conversion on the first radio frequency optical signal through a photodetector to obtain a unidirectional envelope modulated signal, and determines the first radio frequency electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector only includes the frequency spectrum of the baseband signal in the unidirectional envelope modulated signal.

[0038] In addition, in this aspect, the beneficial effects of the above-mentioned various optional implementations can be referred to the beneficial effects of the relevant implementations in the first and second aspects, and will not be repeated here.

[0039] In a fourth aspect, an embodiment of the present application provides a communication device, which includes a coupling module and an optical modulator.

[0040] The coupling module is configured to superimpose the first electrical signal on the first radio frequency electrical signal to obtain a unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to the optical modulator; the first radio frequency electrical signal is determined based on the baseband signal, and the upper envelope and lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component; the carrier in the unidirectional envelope modulated signal is a sine wave.

[0041] The optical modulator is used to optically modulate the unidirectional envelope modulation signal to obtain a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal with a flat lower envelope and a lower envelope amplitude less than or equal to a first value.

[0042] The optical modulator is further configured to send a first radio frequency optical signal.

[0043] The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal. The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0044] It can be seen that the coupling module can add or subtract the baseband amplitude signal from the first RF electrical signal to obtain a unidirectional envelope modulation signal, and then the optical modulator obtains the first RF optical signal based on the unidirectional envelope modulation signal. Among them, the upper envelope or lower envelope of the unidirectional envelope modulation signal is flat, which is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulation signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optically modulating the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper envelope and lower envelope of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulation signal is lower, thereby reducing the transmission optical power, which is conducive to reducing the power consumption of optical devices. In addition, in the scenario where the first RF optical signal is transmitted by optical fiber, the reduction of the transmission optical power is also conducive to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission.

[0045] In an optional embodiment, the first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

[0046] In an optional embodiment, the optical modulator optically modulates the unidirectional envelope modulated signal to obtain a first radio frequency electrical signal, and is specifically used to: superimpose a first bias electrical signal on the unidirectional envelope modulated signal; and optically modulate the unidirectional envelope modulated signal after superimposing the first bias electrical signal to obtain a first radio frequency optical signal.

[0047] In an optional embodiment, the optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0048] In an optional implementation, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, and the first bias electrical signal is a first bias voltage signal; the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0049] In an optional embodiment, the apparatus further includes a baseband module. The baseband module is configured to generate a first electrical signal and output the first electrical signal to the coupling module. The baseband module is further configured to generate a first radio frequency electrical signal and output the first radio frequency electrical signal to the coupling module.

[0050] In an optional embodiment, the apparatus further includes: a baseband module and an upconversion module. The baseband module is configured to generate a first electrical signal and output the first electrical signal to the coupling module. The baseband module is further configured to generate a baseband signal or an intermediate frequency signal corresponding to the baseband signal and output the baseband signal or the intermediate frequency signal corresponding to the baseband signal to the upconversion module. The upconversion module is configured to upconvert the baseband signal or the intermediate frequency signal corresponding to the baseband signal to obtain a first radio frequency electrical signal and output the first radio frequency electrical signal to the coupling module.

[0051] In addition, in this aspect, the beneficial effects of the above-mentioned various optional implementations can be referred to the beneficial effects of the relevant implementations in the first aspect, and will not be repeated here.

[0052] In a fifth aspect, an embodiment of the present application provides a communication device, which includes a low-noise power amplifier, a low-pass filter and an optical modulator.

[0053] a low-noise power amplifier, configured to convert the first radio frequency electrical signal into a second radio frequency electrical signal, and output the second radio frequency electrical signal to a low-pass filter; the upper envelope and the lower envelope of the first radio frequency electrical signal being symmetrical with respect to a DC component, and the second radio frequency electrical signal being a positive half-amplitude signal or a negative half-amplitude signal of the first radio frequency electrical signal with respect to the DC component;

[0054] a low-pass filter configured to: filter the second radio frequency electrical signal to obtain a baseband signal and a baseband signal in the second radio frequency electrical signal; adjust the amplitudes of the baseband signal and the baseband signal in the spectrum to obtain a unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to the optical modulator; wherein the carrier in the unidirectional envelope modulated signal is a sine wave;

[0055] an optical modulator, configured to optically modulate the unidirectional envelope modulation signal to obtain a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal having a flat lower envelope and a lower envelope amplitude less than or equal to a first value;

[0056] The optical modulator is further configured to transmit a first radio frequency optical signal;

[0057] The unidirectional envelope modulated signal is composed of an adjusted baseband signal and an adjusted fundamental frequency signal, and the difference between the amplitude of the baseband component and the amplitude of the fundamental frequency component in the spectrum corresponding to the unidirectional envelope modulated signal is less than or equal to the second value. The unidirectional envelope modulated signal is a radio frequency electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first radio frequency electrical signal; or the unidirectional envelope modulated signal is a radio frequency electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first radio frequency electrical signal.

[0058] As can be seen, the low-pass filter can first convert the first RF electrical signal, which is a full-wave signal, into a second RF electrical signal, which is a half-wave signal. The second RF electrical signal is then filtered and amplitude-adjusted in the spectrum to obtain a unidirectional envelope modulated signal. The optical modulator then obtains the first RF optical signal based on the unidirectional envelope modulated signal. The flat upper or lower envelope of the unidirectional envelope modulated signal facilitates making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal close to zero. Compared to the optical signal obtained by optically modulating the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper and lower envelopes of the optical signal are symmetrical), the first RF optical signal obtained based on the unidirectional envelope modulated signal has a lower average optical power, thereby reducing the transmission optical power and, in turn, reducing the power consumption of optical devices. Furthermore, in scenarios where the first RF optical signal is transmitted via optical fiber, the reduction in transmission optical power also facilitates reducing the nonlinear effects of optical fiber transmission, thereby reducing signal distortion caused by the nonlinear effects of optical fiber transmission.

[0059] In an optional implementation, the low noise power amplifier is a class B low noise power amplifier, or a class AB low noise power amplifier, or a class C low noise power amplifier.

[0060] In an optional embodiment, the optical modulator optically modulates the unidirectional envelope modulated signal to obtain a first radio frequency optical signal, and is specifically used to: superimpose a first bias electrical signal on the unidirectional envelope modulated signal; and optically modulate the unidirectional envelope modulated signal after superimposing the first bias electrical signal to obtain the first radio frequency optical signal.

[0061] In an optional embodiment, the optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0062] In an optional implementation, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, and the first bias electrical signal is a first bias voltage signal; the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0063] In an optional embodiment, the device further includes a baseband module, which is configured to generate a first radio frequency electrical signal and output the first radio frequency electrical signal to a low noise power amplifier.

[0064] In an optional embodiment, the apparatus further includes a baseband module and an upconversion module. The baseband module is configured to generate a baseband signal or an intermediate frequency signal corresponding to the baseband signal, and output the baseband signal or the intermediate frequency signal corresponding to the baseband signal to the upconversion module. The upconversion module is configured to upconvert the baseband signal or the intermediate frequency signal corresponding to the baseband signal to obtain a first radio frequency electrical signal, and output the first radio frequency electrical signal to a low-noise power amplifier.

[0065] In addition, in this aspect, the beneficial effects of the above-mentioned various optional implementations can be referred to the beneficial effects of the relevant implementations in the first aspect, and will not be repeated here.

[0066] In a sixth aspect, an embodiment of the present application provides a communication device comprising a photodetector and a bandpass filter.

[0067] A photoelectric detector is used to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulated signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0068] The photoelectric detector is further used to perform photoelectric conversion on the first radio frequency optical signal to obtain a unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to the bandpass filter; the passband of the photoelectric detector covers the spectrum of the baseband signal in the unidirectional envelope modulated signal.

[0069] A bandpass filter is used to filter the unidirectional envelope modulated signal to obtain a first radio frequency electrical signal; the passband of the bandpass filter only contains the spectrum of the baseband signal in the unidirectional envelope modulated signal; the upper envelope and lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component.

[0070] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0071] It can be seen that the photodetector and the bandpass filter realize the restoration of the first RF optical signal into the first RF electrical signal, simplifying the method of restoring the first RF electrical signal. Among them, the upper envelope or the lower envelope of the unidirectional envelope modulated signal is flat, which is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optical modulation of the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper envelope and lower envelope of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulated signal is lower, thereby reducing the transmission optical power, which is conducive to reducing the power consumption of optical devices. In addition, in the scenario where optical fiber is used to transmit optical signals, the reduction of the transmission optical power is also conducive to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission. In addition, the communication device also converts the first RF optical signal with lower average optical power into a first RF electrical signal with higher power. In a scenario where the communication device also needs to output the first RF electrical signal to the antenna for signal radiation, a higher RF radiation power of the antenna can be achieved with a lower transmission optical power.

[0072] In a seventh aspect, an embodiment of the present application provides a communication device, which includes a photodetector.

[0073] A photoelectric detector is used to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulated signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0074] The photodetector is further configured to perform photoelectric conversion on the first radio frequency optical signal to obtain a unidirectional envelope modulated signal, and determine the first radio frequency electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector only includes the spectrum of the fundamental frequency signal in the unidirectional envelope modulated signal; and the upper envelope and lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component.

[0075] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0076] It can be seen that the photodetector has both the function of photoelectric conversion and the function of filtering out the baseband signal. The photodetector can restore the first RF optical signal to the first RF electrical signal without complex algorithmic processing, simplifying the method of restoring the first RF electrical signal. Among them, the flat upper envelope or the flat lower envelope of the unidirectional envelope modulated signal is conducive to making the lower envelope of the first RF optical signal obtained based on the unidirectional envelope modulated signal flat and the lower envelope amplitude close to zero, that is, the power value corresponding to the lower envelope of the first RF optical signal is close to zero. Compared with the optical signal obtained by optical modulation of the first RF electrical signal (the waveform of the optical signal is the same as the waveform of the first RF electrical signal, and the upper and lower envelopes of the optical signal are symmetrical), the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulated signal is lower, thereby reducing the transmission optical power, which is conducive to reducing the power consumption of optical devices. In addition, in the scenario of using optical fiber to transmit optical signals, the reduction of transmission optical power is also conducive to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission. In addition, the communication device also converts the first RF optical signal with lower average optical power into a first RF electrical signal with higher power. In a scenario where the communication device also needs to output the first RF electrical signal to the antenna for signal radiation, a higher RF radiation power of the antenna can be achieved with a lower transmission optical power.

[0077] In an eighth aspect, the present application also provides a communication device. The communication device may be a first communication device, or it may be a module or unit (for example, a chip, or a chip system, or a circuit) that performs the method / operation / step / action described in the first aspect in the first communication device, or it may be a device that can be matched with the first communication device, and the communication device has the function of implementing some or all of the implementation methods described in the first aspect. Alternatively, the communication device may be a second communication device, or it may be a module or unit (for example, a chip, or a chip system, or a circuit) that performs the method / operation / step / action described in the second aspect in the second communication device, or it may be a device that can be matched with the second communication device, and the communication device has the function of implementing some or all of the functional implementation methods described in the second aspect. The functions may be implemented by hardware, or they may be implemented by hardware executing corresponding software. The hardware or software includes one or more units or modules corresponding to the above functions.

[0078] In one possible design, the communication device may include a processing unit and a communication unit. The processing unit is configured to support the communication device in performing the corresponding functions in the above method. The communication unit is configured to support communication between the communication device and other communication devices. The communication device may also include a storage unit, which is coupled to the processing unit and the communication unit and stores program instructions and data necessary for the communication device.

[0079] In one embodiment, the communication device includes: a processing unit and a communication unit; the processing unit is used to control the communication unit to send and receive data / signaling.

[0080] The processing unit is used to convert the first radio frequency electrical signal into a unidirectional envelope modulated signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0081] The communication unit is configured to send a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value.

[0082] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0083] In addition, in this aspect, other optional implementations of the communication device can refer to the relevant content of the first aspect above and will not be described in detail here.

[0084] In another embodiment, the communication device includes: a communication unit and a processing unit; the processing unit is used to control the communication unit to send and receive data / signaling.

[0085] A communication unit is configured to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulated signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0086] The processing unit is configured to convert the first radio frequency optical signal into a first radio frequency electrical signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component.

[0087] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0088] In addition, in this aspect, other optional implementations of the communication device can refer to the relevant content of the second aspect above and will not be described in detail here.

[0089] As an example, the communication unit may be a transceiver, the storage unit may be a memory, and the processing unit may be a processor. The processor is coupled to the memory, the memory being used to store programs or instructions to the processor. The processor may be configured to cause the communication device to perform the method described in the first or second aspect above when the programs or instructions are executed by the processor. The transceiver may be configured to transmit and receive signals and / or data.

[0090] In one embodiment, the communication device includes: a processor and a transceiver.

[0091] The processor is used to convert the first radio frequency electrical signal into a unidirectional envelope modulated signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0092] The transceiver is used to send a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, and has a flat lower envelope and a lower envelope amplitude less than or equal to a first value.

[0093] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0094] In addition, in this aspect, other optional implementations of the communication device can refer to the relevant content of the first aspect above and will not be described in detail here.

[0095] In another embodiment, the communication device includes: a processor and a transceiver.

[0096] A transceiver is configured to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulated signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0097] The processor is configured to convert the first radio frequency optical signal into a first radio frequency electrical signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component.

[0098] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0099] In addition, in this aspect, other optional implementations of the communication device can refer to the relevant content of the second aspect above and will not be described in detail here.

[0100] In another embodiment, the communication device is a chip or a chip system. The processing unit may also be embodied as a processing circuit or a logic circuit; and the transceiver unit may be an input / output interface, an interface circuit, an output circuit, an input circuit, a pin, or a related circuit on the chip or chip system.

[0101] During implementation, the processor can be used to perform, for example, but not limited to, baseband-related processing; the transceiver can be used to perform, for example, but not limited to, radio frequency transceiver processing. The aforementioned components can be provided on separate chips, or at least partially or entirely on the same chip. For example, the processor can be further divided into an analog baseband processor and a digital baseband processor. The analog baseband processor can be integrated with the transceiver (or communication interface) on the same chip, while the digital baseband processor can be provided on a separate chip. With the continuous advancement of integrated circuit technology, an increasing number of components can be integrated on the same chip. For example, a digital baseband processor can be integrated with multiple application processors (such as, but not limited to, a graphics processor, a multimedia processor, etc.) on the same chip. Such a chip can be referred to as a system on a chip (SoC). Whether each component is provided independently on different chips or integrated on one or more chips often depends on the product design requirements. The embodiments of the present application do not limit the implementation form of the aforementioned components.

[0102] Ninthly, the present application also provides a processor for executing the various methods mentioned above. In the process of executing these methods, the process of sending the above-mentioned signal and receiving the above-mentioned signal in the above-mentioned method can be understood as the process of the processor outputting the above-mentioned signal, and the process of the processor inputting the above-mentioned signal. When outputting the above-mentioned signal, the processor outputs the above-mentioned signal to the transceiver so that the transceiver can transmit it. After being output by the processor, the above-mentioned signal may also need to undergo other processing before reaching the transceiver. Similarly, when the processor receives the above-mentioned input signal, the transceiver receives the above-mentioned signal and inputs it into the processor. Furthermore, after the transceiver receives the above-mentioned signal, the above-mentioned signal may need to undergo other processing before being input into the processor.

[0103] For the sending and receiving operations involved in the processor, unless otherwise specified, or unless they conflict with their actual functions or internal logic in the relevant descriptions, they can be more generally understood as processor output, reception, input and other operations, rather than sending and receiving operations directly performed by the RF circuit and antenna.

[0104] During implementation, the processor may be a processor specifically configured to execute these methods, or may be a processor that executes computer instructions in a memory to execute these methods, such as a general-purpose processor. The memory may be a non-transitory memory, such as a read-only memory (ROM), which may be integrated with the processor on the same chip or disposed on separate chips. The embodiments of the present application do not limit the type of memory or the configuration of the memory and the processor.

[0105] In a tenth aspect, the present application further provides a communication system, which includes the first communication device and the second communication device of the above aspects. In another possible design, the system may also include other devices that interact with the first communication device and / or the second communication device in the solution provided by the present application.

[0106] In an eleventh aspect, the present application provides a computer-readable storage medium storing a computer program. When the computer program is run, the method described in any one of the first or second aspects above is executed.

[0107] In a twelfth aspect, the present application further provides a computer program product comprising instructions, the computer program product comprising: computer program code, which, when the computer program code is run, enables the method described in any one of the first aspect or the second aspect to be executed.

[0108] In a thirteenth aspect, the present application provides a chip system, which includes a processor and an interface, wherein the interface is used to obtain a program or instruction, and the processor is used to call the program or instruction to implement the functions involved in the first aspect, or to call the program or instruction to implement the functions involved in the second aspect. In one possible design, the chip system also includes a memory, which is used to store program instructions and data necessary for the terminal. The chip system can be composed of a chip, or it can include a chip and other discrete devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] FIG1 is a schematic diagram of a system architecture provided in an embodiment of the present application;

[0110] FIG2 is a schematic diagram of an EAM optical modulation provided in an embodiment of the present application;

[0111] FIG3 is a schematic diagram of a DML optical modulation provided in an embodiment of the present application;

[0112] FIG4 is a schematic diagram of a radio frequency electrical signal provided in an embodiment of the present application;

[0113] FIG5 is a schematic diagram of radio frequency optical fiber transmission provided in an embodiment of the present application;

[0114] FIG6 is a schematic diagram of wireless optical communication provided by an embodiment of the present application;

[0115] FIG7 is a schematic diagram of an FTTR provided in an embodiment of the present application;

[0116] FIG8 is a schematic structural diagram of a communication system provided in an embodiment of the present application;

[0117] FIG9 is a schematic diagram of a signal envelope provided in an embodiment of the present application;

[0118] FIG10 is a schematic diagram of a unidirectional envelope signal provided in an embodiment of the present application;

[0119] FIG11 is a schematic diagram of another unidirectional envelope signal provided in an embodiment of the present application;

[0120] FIG12 is a schematic flow chart of a signal transmission method provided in an embodiment of the present application;

[0121] FIG13a is a schematic diagram of a sine wave provided in an embodiment of the present application;

[0122] FIG13 b is a schematic diagram of an incomplete sine wave provided in an embodiment of the present application;

[0123] FIG14 is a schematic diagram of a first radio frequency electrical signal provided in an embodiment of the present application;

[0124] FIG15a is a schematic diagram of a first electrical signal provided in an embodiment of the present application;

[0125] FIG15 b is a schematic diagram of another first electrical signal provided in an embodiment of the present application;

[0126] FIG16 is a schematic diagram of an electric energy spectrum of a unidirectional envelope modulated signal provided in an embodiment of the present application;

[0127] FIG17 is a schematic diagram of converting a first radio frequency electrical signal into a unidirectional envelope modulated signal according to an embodiment of the present application;

[0128] FIG18 is a schematic diagram of a second radio frequency electrical signal provided in an embodiment of the present application;

[0129] FIG19a is a schematic diagram of a spectrum corresponding to a second radio frequency electrical signal provided in an embodiment of the present application;

[0130] FIG19b is a schematic diagram of a spectrum corresponding to a unidirectional envelope modulation signal provided in an embodiment of the present application;

[0131] FIG20a is a schematic diagram of a first radio frequency optical signal provided in an embodiment of the present application;

[0132] FIG20 b is a schematic diagram of an optical signal obtained by optically modulating a first radio frequency electrical signal according to an embodiment of the present application;

[0133] FIG21 is a schematic diagram of optically modulating a unidirectional envelope modulation signal provided by an embodiment of the present application;

[0134] FIG22 is a schematic diagram of another method of optically modulating a unidirectional envelope modulation signal provided by an embodiment of the present application;

[0135] FIG23 is a schematic diagram of a first communication device 2300 provided in an embodiment of the present application;

[0136] FIG24 is a schematic diagram of another first communication device 2300 provided in an embodiment of the present application;

[0137] FIG25 is a schematic diagram of another first communication device 2300 provided in an embodiment of the present application;

[0138] FIG26 is a schematic diagram of a first communication device according to an embodiment of the present application obtaining a first radio frequency optical signal based on a baseband digital signal;

[0139] FIG27 is a schematic diagram of a first communication device 2700 provided in an embodiment of the present application;

[0140] FIG28 is a schematic diagram of another first communication device 2700 provided in an embodiment of the present application;

[0141] FIG29 is a schematic diagram of another first communication device 2700 provided in an embodiment of the present application;

[0142] FIG30 is a schematic diagram of a second communication device 3000 provided in an embodiment of the present application;

[0143] FIG31 is a schematic diagram of a second communication device 3100 provided in an embodiment of the present application;

[0144] FIG32 is a schematic diagram of a second communication device according to an embodiment of the present application obtaining a first radio frequency electrical signal based on a first radio frequency optical signal;

[0145] FIG33 is a schematic structural diagram of a communication device 3300 provided in an embodiment of the present application;

[0146] FIG34 is a schematic structural diagram of a communication device 3400 provided in an embodiment of the present application;

[0147] Figure 35 is a structural diagram of a communication device 3500 provided in an embodiment of the present application. DETAILED DESCRIPTION

[0148] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0149] First, in order to better understand the signal transmission method disclosed in the embodiment of the present application, a communication system to which the embodiment of the present application is applicable is described.

[0150] The technical solutions of the embodiments of the present application can be applied to various communication systems. For example, global mobile communication systems, long term evolution (LTE) systems, universal mobile communication systems, fourth generation mobile communication technology (4G) systems, next generation radio access networks (NG-RAN), new radio (NR) systems, fifth generation mobile communication technology (5G) systems, and with the continuous development of communication technology, the technical solutions of the embodiments of the present application can also be used for subsequent evolved communication systems, such as sixth generation mobile communication technology (6G) systems, seventh generation mobile communication technology (7G) systems, and the like.

[0151] The technical solution of the embodiment of the present application can be applied to wireless access scenarios based on radio frequency optical transmission, for example, it can be applied to wireless fronthaul systems, wireless base station systems, wireless access point systems, etc.; for another example, it can be applied to high optical power downlinks of radio frequency optical transmission systems. Figure 1 is a schematic diagram of a system architecture provided by an embodiment of the present application, and the system architecture may include a central end, an optical fiber transmission segment, and an antenna end. Among them, the central end can be used to generate radio frequency electrical signals, convert radio frequency electrical signals into radio frequency optical signals, and wavelength division multiplexing of radio frequency channels. The optical fiber transmission segment can be used to realize the transmission and amplification of radio frequency optical signals. The antenna end can be used to realize wavelength division multiplexing, convert radio frequency optical signals into radio frequency electrical signals, and transmit radio frequency electrical signals through the antenna.

[0152] Exemplarily, the central end may include an electro-optical conversion device and a wavelength division multiplexer, the optical fiber transmission section may include an optical parametric amplifier (OPA) and an optical fiber, and the antenna end may include a wavelength division multiplexer, a photoelectric diode (PD) and an antenna. The electro-optical conversion device can be used to convert radio frequency electrical signals into radio frequency optical signals. For example, the electro-optical conversion device can be a directly modulated laser (DML), an electroabsorption modulator (EAM) or a Mach-Zehnder modulator (MZM). The wavelength division multiplexer can be used to combine optical signals of different wavelengths, and the wavelength division multiplexer can be used to demultiplex optical signals of multiple wavelengths. The optical amplifier can be used to amplify the optical power of the optical signal. The optical fiber can connect the central end and the antenna end to achieve long-distance low-loss transmission of the radio frequency optical signal. The PD can be used to convert the radio frequency optical signal into a radio frequency electrical signal. The antenna can be used to achieve spatial radiation and reception of the radio frequency electrical signal.

[0153] Among them, EAM and MZM realize optical modulation by changing voltage, and DML realizes optical modulation by changing current. Taking the DC component of the RF electrical signal input to EAM or DML as 0 as an example, the embodiment of the present application provides a schematic diagram of EAM optical modulation as shown in Figure 2, and a schematic diagram of DML optical modulation as shown in Figure 3. In Figure 2, the power-voltage curve represents the relationship between the working voltage and optical power of the EAM, and the voltage-time curve represents the RF electrical signal input to the EAM superimposed on the bias voltage signal (the voltage corresponding to the bias voltage signal is V bias ) after the EAM superimposes the bias voltage signal on the RF electrical signal. The power-time curve represents the RF optical signal obtained by the EAM optically modulating the RF electrical signal superimposed on the bias voltage signal. In Figure 3, the power-current curve represents the relationship between the operating current and optical power of the DML, and the current-time curve represents the RF electrical signal input to the DML superimposed on the bias current signal (the current corresponding to the bias current signal is I bias ), the power-time curve represents the RF optical signal obtained by DML optically modulating the RF electrical signal superimposed with the bias current signal.

[0154] The following explanation uses the EAM optical modulation shown in Figure 2 as an example. DML optical modulation is similar and will not be further described. Referring to Figure 2, applying a bias voltage signal to the EAM causes the EAM's bias voltage to be the voltage corresponding to the bias voltage signal. Therefore, when the EAM performs optical modulation, its operating voltage is set according to the electrical signal represented by the voltage-time curve in Figure 2 (i.e., the electrical signal resulting from the superposition of the bias voltage signal and the RF electrical signal input to the EAM), resulting in an RF optical signal represented by the power-time curve in Figure 2. If the voltage corresponding to the bias voltage signal is set to an appropriate value (i.e., the EAM's bias voltage is set to an appropriate value) so that the EAM's operating voltage falls within the linear region of the power-voltage curve, the EAM can perform linear optical modulation, and the resulting optical signal can have the same waveform as the complete RF electrical signal input to the EAM. For example, if the RF electrical signal shown in Figure 4 is input to the EAM, and the EAM's bias voltage is set to a voltage midway within the linear region of the power-voltage curve, the EAM can perform optical modulation to produce an RF optical signal with a waveform that is identical or substantially identical to the complete waveform of the RF electrical signal shown in Figure 4.

[0155] The technical solutions of the embodiments of the present application can also be applied to radio frequency optical communication scenarios, including radio frequency optical fiber transmission scenarios and wireless optical communication scenarios. Among them, the radio frequency optical fiber transmission scenario is shown in Figure 5, for example. The radio frequency optical fiber transmission scenario may include a baseband processing unit (BBU) and a radio frequency remote head (RRH), and the BBU and the RRH communicate based on optical fiber. In one scenario, the BBU can convert the first radio frequency electrical signal into a one-way envelope modulation signal, and send the first radio frequency optical signal obtained by optically modulating the one-way envelope modulation signal; the RRH can convert the received first radio frequency optical signal into a first radio frequency electrical signal. In another scenario, the RRH can convert the first radio frequency electrical signal into a one-way envelope modulation signal, and send the first radio frequency optical signal obtained by optically modulating the one-way envelope modulation signal; the BBU can convert the received first radio frequency optical signal into a first radio frequency electrical signal.

[0156] A wireless optical communication scenario is shown in FIG6 , for example. The wireless optical communication scenario may include two terminal devices based on wireless optical communication, one of which may be used to convert a first radio frequency electrical signal into a unidirectional envelope modulated signal and transmit a first radio frequency optical signal obtained by optically modulating the unidirectional envelope modulated signal; the other terminal device may be used to convert the received first radio frequency optical signal into a first radio frequency electrical signal. In the embodiments of the present application, the terminal device may also be referred to as user equipment (UE), terminal, access terminal, subscriber unit, user station, mobile station, mobile station (MS), remote station, remote terminal, mobile device, user terminal, user agent, or user device. The terminal device may also be a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, etc.

[0157] The technical solutions provided by the embodiments of the present application can also be applied to centralized Wi-Fi access networks (C-WANs) in fiber-to-the-room (FTTR) or fiber-to-the-radio (C-WANs). For example, they can be applied to the downlink high-power RF link from the master optical network unit (ONU) to the slave ONU in the FTTR, as shown in Figure 7. Furthermore, the technical solutions provided by the embodiments of the present application can support not only RF signal transmission for communication but also RF signal transmission for sensing.

[0158] Please refer to Figure 8, which is a structural diagram of a communication system provided in an embodiment of the present application, wherein the communication system includes a first communication device and a second communication device. The first communication device can be used to convert a first radio frequency electrical signal into a unidirectional envelope modulated signal, and send a first radio frequency optical signal obtained by optically modulating the unidirectional envelope modulated signal. The second communication device can be used to receive the first radio frequency optical signal and convert the first radio frequency optical signal into a first radio frequency electrical signal. The communication system can also include a channel between the first communication device and the second communication device for transmitting the first radio frequency optical signal, such as an optical fiber, space or other transmission medium. The optical fiber transmission link based on optical fiber transmission of optical signals can adopt single-wave transmission or wavelength division multiplexing transmission, and the optical fiber transmission link can include devices such as optical fibers, optical amplifiers, wavelength division multiplexers, and wavelength division multiplexers. In addition, in an embodiment of the present application, the first communication device can also be referred to as a radio frequency light generation module, and the second communication device can also be referred to as a radio frequency recovery module.

[0159] For example, the first communication device may be the central end in the system architecture shown in FIG1 or deployed in the central end, and the second communication device may be the antenna end in the system architecture shown in FIG1 or deployed in the antenna end. Alternatively, the first communication device may be the BBU in FIG5 or deployed in the BBU, and the second communication device may be the RRH in FIG5 or deployed in the RRH. Alternatively, the first communication device may be the RRH in FIG5 or deployed in the RRH, and the second communication device may be the BBU in FIG5 or deployed in the BBU. Alternatively, the first communication device may be a terminal device in FIG6 or deployed in the terminal device, and the second communication device may be another terminal device in FIG6 or deployed in the another terminal device. Alternatively, the first communication device may be the master ONU in FIG7 or deployed in the master ONU, and the second communication device may be the slave ONU in FIG7 or deployed in the slave ONU. Furthermore, the first communication device and the second communication device may be other applicable devices in the applicable scenarios of the technical solutions of the embodiments of the present application, or the first communication device and the second communication device may be other applicable devices in the applicable scenarios of the technical solutions of the embodiments of the present application, without limitation.

[0160] Next, a brief introduction is given to the relevant concepts involved in the embodiments of this application.

[0161] 1. Signal envelope

[0162] The signal envelope is obtained by smoothly connecting the signal's extreme points. The upper envelope is obtained by smoothly connecting the signal's maximum points, and the lower envelope is obtained by smoothly connecting the signal's minimum points. For example, referring to Figure 9, smoothly connecting the signal's maximum points yields the upper envelope (shown by the black dashed line without the black rectangle) in Figure 9. Smoothly connecting the signal's minimum points yields the lower envelope (shown by the black dashed line with the black rectangle) in Figure 9.

[0163] The envelope amplitude of a signal can be expressed based on its DC component. For example, if the amplitude corresponding to the DC component of a signal is r0, and the signal has a maximum value r1 at time t1 and a minimum value r2 at time t2, then the amplitude of the upper envelope of the signal at time t1 is r1-r0, and the amplitude of the lower envelope at time t2 is r2-r0. If the DC component of the signal is zero, i.e., r0 = 0, then the amplitude of the upper envelope of the signal at time t1 is r1, and the amplitude of the lower envelope at time t2 is r2.

[0164] 2. Unidirectional envelope signal

[0165] A unidirectional envelope signal is one in which the lower envelope is flat and the upper envelope has significant fluctuations, or a signal in which the upper envelope is flat and the lower envelope has significant fluctuations. It can be seen that the upper and lower envelopes of a unidirectional envelope signal are asymmetric with respect to the DC component. For example, as shown in Figures 10 and 11, the lower envelope of the unidirectional envelope signal shown in Figure 10 is flat and the upper envelope has significant fluctuations, while the upper envelope of the unidirectional envelope signal shown in Figure 11 is flat and the lower envelope has significant fluctuations.

[0166] In addition, a unidirectional envelope signal as an RF electrical signal may also be referred to as a unidirectional envelope RF electrical signal, and a unidirectional envelope signal as an RF optical signal may also be referred to as a unidirectional envelope RF optical signal. The unidirectional envelope modulated signal involved in the embodiments of the present application is a unidirectional envelope RF electrical signal, and the first RF optical signal is a unidirectional envelope RF optical signal.

[0167] 3. Full-wave signal and half-wave signal

[0168] A full-wave signal is one whose waveform is envelope-symmetrical with respect to its DC component. In other words, the upper and lower envelopes of a full-wave signal are symmetrical with respect to the DC component. For example, the signal shown in Figure 4 is envelope-symmetrical with respect to the DC component indicated by the black dashed line. Therefore, the signal shown in Figure 4 is a full-wave signal.

[0169] A half-wave signal is a signal that has the positive half-amplitude or negative half-amplitude of the full-wave signal relative to the DC component. The positive half-amplitude of the full-wave signal relative to the DC component, i.e., the upper half of the amplitude of the full-wave signal relative to the DC component, is greater than or equal to the amplitude of the DC component. The negative half-amplitude of the full-wave signal relative to the DC component, i.e., the lower half of the amplitude of the full-wave signal relative to the DC component, is less than or equal to the amplitude of the DC component.

[0170] The first radio frequency electrical signal involved in the embodiment of the present application is a full-wave signal, and the second radio frequency electrical signal is a half-wave signal.

[0171] The following is a detailed description of the embodiments of the present application in conjunction with the accompanying drawings. The flowchart in the present application uses the first communication device and the second communication device as an example to illustrate the corresponding method, but the present application does not limit the execution subject of the interactive diagram. For example, the first communication device in the figure can also be a chip or chip system or processor that supports the first communication device to implement the corresponding method, or a logic module or software that can implement all or part of the functions of the first communication device; the second communication device in the figure can also be a chip or chip system or processor that supports the second communication device to implement the corresponding method, or a logic module or software that can implement all or part of the functions of the second communication device.

[0172] Please refer to FIG. 12 , which is a flow chart of a signal transmission method provided in an embodiment of the present application. The signal transmission method is described from the perspective of interaction between a first communication device and a second communication device. The signal transmission method includes the following steps:

[0173] S101: A first communication device converts a first radio frequency electrical signal into a unidirectional envelope modulated signal.

[0174] The upper and lower envelopes of the first RF electrical signal are symmetrical with respect to the DC component. The carrier wave in the unidirectional envelope modulated signal is a sine wave; that is, the carrier wave in the unidirectional envelope modulated signal is a complete periodic signal within each cycle, and the signal waveform is a sine wave. For example, the carrier wave in the unidirectional envelope modulated signal can be a complete sine wave within each cycle as shown in FIG13a, rather than an incomplete sine wave within each cycle as shown in FIG13b (the signal shown in FIG13b only has a partial sine wave within each cycle).

[0175] The unidirectional envelope modulation signal is a radio frequency electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulation signal corresponds to the upper envelope of the first radio frequency electrical signal. Alternatively, the unidirectional envelope modulation signal is a radio frequency electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulation signal corresponds to the lower envelope of the first radio frequency electrical signal. The embodiment of the present application does not limit the lower envelope flatness to the absolute unchanged lower envelope amplitude. In addition to the possibility that the lower envelope amplitude is absolutely unchanged, the lower envelope flatness may also be manifested as a slight change in the lower envelope amplitude. The embodiment of the present application also does not limit the upper envelope flatness to the absolute unchanged upper envelope amplitude. In addition to the possibility that the upper envelope amplitude is absolutely unchanged, the upper envelope flatness may also be manifested as a slight change in the upper envelope amplitude.

[0176] It is understandable that when the DC component of the first RF electrical signal is 0, the envelope signal of the unidirectional envelope modulation signal is modulated in a unidirectional direction in the positive or negative direction, while the amplitude of the envelope signal in the other direction remains unchanged or changes slightly. Specifically, when the DC component of the first RF electrical signal is 0, if the upper envelope of the unidirectional envelope modulation signal is flat and the lower envelope corresponds to the lower envelope of the first RF electrical signal, it can be said that the envelope signal of the unidirectional envelope modulation signal is unidirectionally modulated in the positive direction, and the waveform of the unidirectional envelope modulation signal is shown in Figure 10 for example; when the lower envelope of the unidirectional envelope modulation signal is flat and the upper envelope corresponds to the upper envelope of the first RF electrical signal, it can be said that the envelope signal of the unidirectional envelope modulation signal is unidirectionally modulated in the negative direction, and the waveform of the unidirectional envelope modulation signal is shown in Figure 11 for example. In addition, in an embodiment of the present application, in a scenario where the DC component of the first RF electrical signal is 0, when the lower envelope of the unidirectional envelope modulation signal is flat and the upper envelope corresponds to the upper envelope of the first RF electrical signal, the unidirectional envelope modulation signal can also be called a forward unidirectional envelope modulation signal; when the upper envelope of the unidirectional envelope modulation signal is flat and the lower envelope corresponds to the lower envelope of the first RF electrical signal, the unidirectional envelope modulation signal can also be called a reverse unidirectional envelope modulation signal.

[0177] Optionally, the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal, which can be specifically expressed as follows: there is a multiple relationship between the upper envelope amplitude of the unidirectional envelope modulated signal and the upper envelope amplitude of the first RF electrical signal. The lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal, which can be specifically expressed as follows: there is a multiple relationship between the lower envelope amplitude of the unidirectional envelope modulated signal and the lower envelope amplitude of the first RF electrical signal. For example, the DC component of the first RF electrical signal shown in Figure 14 is 0, and the upper envelope and lower envelope of the first RF electrical signal are symmetrical relative to the DC component; the unidirectional envelope modulated signal obtained by converting the first RF electrical signal shown in Figure 14 can be shown in Figure 10 or Figure 11. The lower envelope of the unidirectional envelope modulated signal shown in Figure 10 is flat, and the upper envelope amplitude of the unidirectional envelope modulated signal is twice the upper envelope amplitude of the first RF electrical signal shown in Figure 14. The upper envelope of the unidirectional envelope modulation signal shown in FIG11 is flat, and the lower envelope amplitude of the unidirectional envelope modulation signal is twice the lower envelope amplitude of the first RF electrical signal shown in FIG14 .

[0178] The following describes an optional manner in which the first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulated signal, as described in the following optional implementations 1.1 and 1.2.

[0179] In embodiment 1.1, the first communication device converting the first radio frequency electrical signal into a unidirectional envelope modulated signal may include: the first communication device determining the unidirectional envelope modulated signal based on the first radio frequency electrical signal and the first electrical signal. The first radio frequency electrical signal is determined based on a baseband signal. The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal.

[0180] For example, the first radio frequency electrical signal S0(t) may be expressed as follows:

[0181] Where I(t) is the in-phase component (I component) corresponding to the baseband signal, Q(t) is the quadrature component (Q component) corresponding to the baseband signal; A(t) is the baseband amplitude signal corresponding to the baseband signal, φ(t) is the phase signal corresponding to the baseband signal; ω RF It is understandable that the first electrical signal may be A(t), or the first electrical signal may be -A(t).

[0182] Optionally, the first communication device determines the unidirectional envelope modulation signal based on the first RF electrical signal and the first electrical signal, which may include: the first communication device superimposing the first electrical signal on the first RF electrical signal to obtain the unidirectional envelope modulation signal. In other words, the first communication device may add a baseband amplitude signal corresponding to the baseband signal to the first RF electrical signal, or subtract the baseband amplitude signal corresponding to the baseband signal from the first RF electrical signal to obtain the unidirectional envelope modulation signal. In addition, the baseband amplitude signal and the first RF electrical signal are separated in the spectrum, and the operation of the first communication device superimposing the first electrical signal on the first RF electrical signal causes little damage to the first RF electrical signal and is easy to implement in the baseband.

[0183] For example, when the first RF electrical signal S0(t) is as shown in the above formula (1), the unidirectional envelope modulation signal S1(t) may be as shown in the following formula (2):

[0184] S1(t)=A(t)sin(ω RF t+φ(t))±A(t)=A(t)[sin(ω RF t+φ(t))±1] (2)

[0185] Where A(t)≥0. In S1(t)=A(t)[sin(ω RF t+φ(t))+1], that is, when the first electrical signal is the baseband amplitude signal corresponding to the baseband signal, S1(t)≥0, the lower envelope of the unidirectional envelope modulation signal is flat and the upper envelope corresponds to the upper envelope of the first RF electrical signal. RF t+φ(t))-1], that is, when the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal, S1(t)≤0, the upper envelope of the unidirectional envelope modulated signal is flat and the lower envelope corresponds to the lower envelope of the first RF electrical signal.

[0186] For example, if the first electrical signal is a baseband amplitude signal corresponding to the baseband signal, the first communication device may superimpose the first electrical signal shown in FIG15a (the first electrical signal is the baseband amplitude signal corresponding to the baseband signal) on the first RF electrical signal shown in FIG14, to obtain a unidirectional envelope modulated signal having a waveform as shown in FIG10. For another example, if the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal, the first communication device may superimpose the first electrical signal shown in FIG15b (the first electrical signal is the electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal) on the first RF electrical signal shown in FIG14, to obtain a unidirectional envelope modulated signal having a waveform as shown in FIG11.

[0187] It is understood that the spectrum corresponding to the unidirectional envelope modulated signal is composed of a baseband component corresponding to the baseband amplitude signal and a fundamental frequency component corresponding to the first RF electrical signal. In the spectrum corresponding to the unidirectional envelope modulated signal, the difference between the amplitude of the baseband component and the amplitude of the fundamental frequency component is less than or equal to a second value. This second value can be relatively small, that is, the amplitude of the baseband component is the same as or close to the amplitude of the fundamental frequency component. Accordingly, in the electric power spectrum corresponding to the unidirectional envelope modulated signal, the amplitude corresponding to the frequency of the baseband amplitude signal is equal to or close to the amplitude corresponding to the frequency of the first RF electrical signal. For example, the electric power spectrum corresponding to the unidirectional envelope modulated signal may be as shown in FIG16.

[0188] Optionally, the first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal. Specifically, in the case where the first electrical signal is a baseband amplitude signal corresponding to the baseband signal, the amplitude of the first electrical signal is the same as the upper envelope amplitude of the first radio frequency electrical signal; in the case where the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal, the amplitude of the first electrical signal is the same as the lower envelope amplitude of the first radio frequency electrical signal. In addition, in order to make the first electrical signal time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal, it can be achieved by any one or more of the following optional methods 1 to 6:

[0189] Method 1: The amplitude and delay of the baseband signal and the baseband amplitude signal are adjusted by digital delay. The baseband signal is used to determine the first radio frequency electrical signal, and the baseband amplitude signal corresponds to the baseband signal.

[0190] Method 2: Use digital delay to adjust the amplitude and delay of the intermediate frequency signal and baseband amplitude signal. The intermediate frequency signal is obtained by up-converting the baseband signal. The intermediate frequency signal is used to determine the first radio frequency electrical signal, and the baseband amplitude signal corresponds to the baseband signal.

[0191] Method 3: Adjusting the amplitude and delay of the first RF electrical signal and the baseband amplitude signal through digital delay. The baseband amplitude signal corresponds to the baseband signal, which is used to determine the first RF electrical signal.

[0192] Method 4: Adjusting the length of a transmission line used to transmit a baseband amplitude signal and / or a transmission line used to transmit a baseband signal, and performing amplification, attenuation, and / or delay processing on the baseband amplitude signal and / or the baseband signal. The baseband signal is used to determine the first radio frequency electrical signal, and the baseband amplitude signal corresponds to the baseband signal.

[0193] Method 5: Adjust the length of the transmission line used to transmit the baseband amplitude signal and / or the length of the transmission line used to transmit the intermediate frequency signal, and amplify, attenuate, and / or delay the baseband amplitude signal and / or intermediate frequency signal. The intermediate frequency signal is obtained by up-converting the baseband signal. The intermediate frequency signal is used to determine the first RF electrical signal. The baseband amplitude signal corresponds to the baseband signal.

[0194] Method 6: Adjust the length of a transmission line used to transmit the baseband amplitude signal and / or the length of a transmission line used to transmit the first RF electrical signal, and amplify, attenuate, and / or delay the baseband amplitude signal and / or the first RF electrical signal. The baseband amplitude signal corresponds to a baseband signal, and the baseband signal is used to determine the first RF electrical signal.

[0195] In implementation 1.2, the first communication device converts the first radio frequency electrical signal into a one-way envelope modulated signal, which may include: the first communication device converts the first radio frequency electrical signal into a second radio frequency electrical signal; the first communication device filters the second radio frequency electrical signal to obtain a baseband signal and a baseband signal in the second radio frequency electrical signal; the first communication device adjusts the amplitude of the baseband signal and the baseband signal in the second radio frequency electrical signal on the spectrum to obtain a one-way envelope modulated signal. It can be seen that the first communication device can convert the first radio frequency electrical signal into a one-way envelope modulated signal by first converting the first radio frequency electrical signal as a full-wave signal into a second radio frequency electrical signal as a half-wave signal, and then converting the second radio frequency electrical signal as a half-wave signal into a one-way envelope modulated signal, as shown in Figure 17. In addition, this implementation can be implemented on the radio frequency link, does not include baseband processing, and can reduce the impact of baseband processing on the signal.

[0196] The second RF electrical signal is a positive half-amplitude signal or a negative half-amplitude signal of the first RF electrical signal relative to the DC component. That is, the second RF electrical signal is an RF electrical signal having a positive half-amplitude or a negative half-amplitude of the first RF electrical signal relative to the DC component. The carrier in the second RF electrical signal has a half-cycle signal in each cycle; for example, the carrier in the second RF electrical signal has a sinusoidal waveform in half of each cycle, and the carrier does not exist in the other half of each cycle. That is, the value of the carrier in the other half of each cycle is zero, as shown in Figure 13b.

[0197] The embodiment of the present application does not limit the second radio frequency electrical signal to have the absolute positive half amplitude or absolute negative half amplitude of the first radio frequency electrical signal relative to the DC component. It is understandable that, in addition to having all the positive half amplitude or all the negative half amplitude of the first radio frequency electrical signal relative to the DC component, the second radio frequency electrical signal may also have most of the positive half amplitude or most of the negative half amplitude of the first radio frequency electrical signal relative to the DC component; or, it may also have all the positive half amplitude and a small part of the negative half amplitude of the first radio frequency electrical signal relative to the DC component, or have all the negative half amplitude and a small part of the positive half amplitude of the first radio frequency electrical signal relative to the DC component; or, it may also have most of the positive half amplitude and a small part of the negative half amplitude of the first radio frequency electrical signal relative to the DC component, or have most of the negative half amplitude and a small part of the positive half amplitude of the first radio frequency electrical signal relative to the DC component. For example, taking the first radio frequency electrical signal as shown in Figure 4 as an example, the possible waveforms of the second radio frequency electrical signal are shown in parts (A) to (D) of Figure 18, and the black dotted lines in parts (A) to (D) of Figure 18 represent the DC component corresponding to the first radio frequency electrical signal shown in Figure 4. In Figure 18, the second RF electrical signal shown in part (A) has the entire positive half-amplitude of the first RF electrical signal shown in Figure 4 relative to the DC component, the second RF electrical signal shown in part (B) has the entire positive half-amplitude and a small part of the negative half-amplitude of the first RF electrical signal shown in Figure 4 relative to the DC component, the second RF electrical signal shown in part (C) has most of the positive half-amplitude of the first RF electrical signal shown in Figure 4 relative to the DC component, and the second RF electrical signal shown in part (D) has most of the positive half-amplitude and a small part of the negative half-amplitude of the first RF electrical signal shown in Figure 4 relative to the DC component.

[0198] In addition, in this embodiment 1.2, the unidirectional envelope modulated signal is composed of an adjusted baseband signal and an adjusted fundamental frequency signal in the second RF electrical signal; the difference between the amplitude of the baseband component and the amplitude of the fundamental frequency component in the spectrum corresponding to the unidirectional envelope modulated signal is less than or equal to the second value. It can be seen that the first communication device filters the second RF electrical signal to filter out the high-order harmonic components in the second RF electrical signal, while retaining the baseband signal and fundamental frequency signal in the second RF electrical signal. Compared to the second RF electrical signal, the unidirectional envelope modulated signal has fewer harmonic components, so the bandwidth requirement for the optical modulator when optically modulating the unidirectional envelope modulated signal is lower than the bandwidth requirement for the optical modulator when optically modulating the second RF electrical signal. In addition, the second value can be predefined and is not limited. The second value can be set to a smaller value, so that the amplitude of the baseband component and the amplitude of the fundamental frequency component in the spectrum corresponding to the unidirectional envelope modulated signal are equal to or close to each other.

[0199] For example, combining Figure 19a and Figure 19b, Figure 19a shows the spectrum corresponding to the second RF electrical signal, and Figure 19b shows the spectrum corresponding to the unidirectional envelope modulated signal; it can be seen that the spectrum corresponding to the second RF electrical signal includes not only baseband components and fundamental frequency components, but also higher-order harmonic components such as 2nd-order harmonic components and 4th-order harmonic components; the spectrum corresponding to the unidirectional envelope modulated signal includes baseband components and fundamental frequency components, but does not include higher-order harmonic components.

[0200] For another example, the amplitude of the baseband component in the spectrum corresponding to the second radio frequency electrical signal shown in FIG19a is 0.318, and the amplitude of the fundamental frequency component is 0.5. The first communication device can increase the amplitude of the baseband signal in the spectrum of the second radio frequency electrical signal by times, so that the amplitude of the baseband component in the spectrum corresponding to the unidirectional envelope modulation signal shown in Figure 19b is approximately 0.5, and the amplitude of the fundamental frequency component is 0.5.

[0201] Optionally, the operation of the first communication device converting the first RF electrical signal into the second RF electrical signal can be achieved by the first communication device through a low-noise power amplifier, which can be used to process the first RF electrical signal as a full-wave signal to obtain the second RF electrical signal as a half-wave signal. The low-noise power amplifier can be, for example, a low noise amplifier (LNA).

[0202] For example, the low-noise power amplifier can be a Class B low-noise power amplifier (e.g., a Class B LNA), which has a small adjacent channel leakage power ratio (ACLR). The second RF electrical signal generated by the Class B low-noise power amplifier can accurately intercept the amplitude midpoint of the first RF electrical signal (i.e., the position of the DC component corresponding to the first RF electrical signal). In other words, the second RF electrical signal obtained using the Class B low-noise power amplifier can have the full positive half-amplitude or the full negative half-amplitude of the first RF electrical signal relative to the DC component. For another example, if the ACLR performance requirements permit, the low-noise power amplifier can also be a Class AB low-noise power amplifier (e.g., a Class AB LNA) or a Class C low-noise power amplifier (e.g., a Class C LNA). The ACLR of the Class AB low-noise power amplifier and the ACLR of the Class C low-noise power amplifier are both slightly higher than the ACLR of the Class B low-noise power amplifier.

[0203] In an optional embodiment, the method may further include: the first communication device generating a first radio frequency electrical signal. Optional manners for the first communication device to generate the first radio frequency electrical signal may be as described in the following optional embodiments 2.1 to 2.3.

[0204] In embodiment 2.1, the first radio frequency electrical signal may be an analog signal obtained by sequentially performing modulation, digital-to-analog conversion, and up-conversion on a baseband digital signal (i.e., a baseband signal in the digital domain). The first communication device generating the first radio frequency electrical signal may include: the first communication device modulating the baseband digital signal to convert the baseband digital signal into a digital baseband modulated signal; the first communication device then performing digital-to-analog conversion on the digital baseband modulated signal to obtain a baseband analog signal (i.e., a baseband signal in the analog domain); and the first communication device then performing up-conversion on the baseband analog signal to obtain the first radio frequency electrical signal.

[0205] In embodiment 2.2, the first radio frequency electrical signal may be an analog signal obtained by sequentially performing modulation, a first up-conversion process, a digital-to-analog conversion, and a second up-conversion process on a baseband digital signal (i.e., a baseband signal in the digital domain). The first communication device generating the first radio frequency electrical signal may include: the first communication device modulating the baseband digital signal to convert the baseband digital signal into a digital baseband modulated signal; the first communication device then performing digital up-conversion on the digital baseband modulated signal to obtain a digital intermediate frequency signal; the first communication device performing digital-to-analog conversion on the digital intermediate frequency signal to obtain an intermediate frequency signal as an analog signal; and then the first communication device performing up-conversion on the intermediate frequency signal to obtain the first radio frequency electrical signal.

[0206] In embodiment 2.3, the first radio frequency electrical signal may be an analog signal obtained by sequentially modulating, up-converting, and converting a baseband digital signal (i.e., a baseband signal in the digital domain). The first communication device generating the first radio frequency electrical signal may include: the first communication device modulating the baseband digital signal to convert the baseband digital signal into a digital baseband modulated signal; the first communication device then up-converting the digital baseband modulated signal to obtain a digital radio frequency signal; and the first communication device then up-converting the digital radio frequency signal to obtain the first radio frequency electrical signal.

[0207] Additionally, optionally, in the case where the first communication device converts the first RF electrical signal into a unidirectional envelope modulated signal using Implementation 1.1, in any of Implementations 2.1 to 2.3 above, the method may further include: the first communication device generating a first electrical signal. The first communication device may determine a digital envelope signal of the digital baseband modulated signal as the first electrical signal.

[0208] In another optional embodiment, the method may further include: the first communication device receiving a first radio frequency electrical signal. For example, the first radio frequency electrical signal may be generated by a device different from the first communication device and the second communication device and then transmitted to the first communication device, or may be received by the first communication device via an antenna.

[0209] Among them, in the case where the first radio frequency electrical signal is generated by another device different from the first communication device and the second communication device and then sent to the first communication device, the first communication device may adopt the above-mentioned embodiment 1.1 or embodiment 1.2 to realize the conversion of the first radio frequency electrical signal into a unidirectional envelope modulation signal. If the first communication device adopts the above-mentioned embodiment 1.1 to realize the conversion of the first radio frequency electrical signal into a unidirectional envelope modulation signal, the communication device that generates and sends the first radio frequency electrical signal also needs to generate a first electrical signal and send the first electrical signal to the first communication device. In addition, the optional method for generating the first radio frequency electrical signal by another device different from the first communication device and the second communication device may be similar to any one or more of the above-mentioned embodiments 2.1 to 2.3, and will not be repeated here.

[0210] When the first RF electrical signal is received by the first communication device via an antenna, the first communication device may convert the first RF electrical signal into a unidirectional envelope modulated signal using the above-described embodiment 1.2. The method of the first communication device receiving the first RF electrical signal via an antenna may be applied to a scenario where the first communication device is an RRH or is deployed in an RRH, and the second communication device is a BBU or is deployed in a BBU.

[0211] S102: The first communication device sends a first radio frequency optical signal; correspondingly, the second communication device receives the first radio frequency optical signal.

[0212] The first RF optical signal is a unidirectional envelope RF optical signal obtained by optically modulating a unidirectional envelope modulation signal, having a flat lower envelope and a lower envelope amplitude less than or equal to a first value. The first value may be predefined and set to a relatively small value, that is, the lower envelope amplitude of the first RF optical signal is equal to or close to zero. Furthermore, the carrier in the first RF optical signal is a sinusoidal wave, that is, the RF carrier in the first RF optical signal has a complete sinusoidal waveform within each cycle.

[0213] Compared to the optical signal obtained by optically modulating the first radio frequency electrical signal, in which the upper envelope and the lower envelope are symmetrical relative to the DC component, the average optical power of the first radio frequency optical signal is lower, thereby reducing the transmission optical power between the first communication device and the second communication device, thereby helping to reduce the power consumption of optical devices. In addition, in the scenario where optical fiber is used to transmit optical signals between the first communication device and the second communication device, the reduction in transmission optical power is also beneficial to reducing the nonlinear effect of optical fiber transmission, thereby reducing the signal distortion caused by the nonlinear effect of optical fiber transmission. For example, the first radio frequency optical signal obtained based on the unidirectional envelope modulation signal is shown in Figure 20a, the optical signal obtained by optically modulating the first radio frequency electrical signal is shown in Figure 20b, and the waveform of the carrier in the first radio frequency optical signal shown in Figure 20a is shown in Figure 13a. It can be seen that the lower envelope of the first radio frequency optical signal shown in Figure 20a is flat and the lower envelope amplitude is close to zero (that is, the power value corresponding to the lower envelope is close to zero), and the average optical power of the first radio frequency optical signal shown in Figure 20a is lower than the average optical power of the optical signal shown in Figure 20b.

[0214] In an optional embodiment, the method may further include: the first communication device optically modulating the unidirectional envelope modulated signal to obtain a first radio frequency optical signal. Optionally, the first communication device optically modulating the unidirectional envelope modulated signal to obtain the first radio frequency optical signal may include: the first communication device superimposing a first bias electrical signal on the unidirectional envelope modulated signal; the first communication device optically modulating the unidirectional envelope modulated signal after superimposing the first bias electrical signal to obtain the first radio frequency optical signal. Optionally, the operations of the first communication device superimposing the first bias electrical signal on the unidirectional envelope modulated signal and the operations of the first communication device optically modulating the unidirectional envelope modulated signal after superimposing the first bias electrical signal may be implemented by the first communication device through an optical modulator. Depending on the driving requirements of the optical modulator, a unidirectional envelope modulated signal with a flat lower envelope and an upper envelope corresponding to the upper envelope of the first radio frequency electrical signal may be selected for optical modulation, or a unidirectional envelope modulated signal with a flat upper envelope and a lower envelope corresponding to the lower envelope of the first radio frequency electrical signal may be selected for optical modulation.

[0215] In addition, the optical modulator can be, for example, a directly modulated laser, an electro-absorption modulator, or a Mach-Zehnder modulator. A directly modulated laser is a laser that achieves optical modulation by changing the current. For example, a directly modulated laser can be a DML. An electro-absorption modulator and a Mach-Zehnder modulator are lasers that achieve optical modulation by changing the voltage. For example, an electro-absorption modulator can be an EAM, and a Mach-Zehnder modulator can be an MZM. The following describes the following cases, respectively, in which the optical modulator is a directly modulated laser, an electro-absorption modulator, or a Mach-Zehnder modulator, as described in the following optional embodiments 3.1 and 3.2.

[0216] Implementation 3.1: The optical modulator is a directly modulated laser. In this case, the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current. The lower envelope of the unidirectional envelope modulation signal used by the directly modulated laser for optical modulation is flat, and the upper envelope corresponds to the upper envelope of the first RF electrical signal; when the DC component of the first RF electrical signal is zero, the directly modulated laser can use a positive unidirectional envelope modulation signal for optical modulation.

[0217] Understandably, the first bias current signal acts on the direct-modulated laser, causing the bias current of the direct-modulated laser to be the current corresponding to the first bias current signal. The direct-modulated laser optically modulates the unidirectional envelope modulation signal superimposed with the first bias current signal. That is, the direct-modulated laser, whose bias current is the current corresponding to the first bias current signal, optically modulates the unidirectional envelope modulation signal. During this optical modulation process, the operating current of the direct-modulated laser is set according to the unidirectional envelope modulation signal superimposed with the first bias current signal. The current corresponding to the first bias current signal is less than the first current, so that the average optical power of the first RF optical signal is less than the optical power obtained by optically modulating the direct-modulated laser when the operating current is the first current.

[0218] For example, taking the case where the DC component corresponding to the first RF electrical signal is 0 as an example, in conjunction with Figure 21, in Figure 21, the power-current curve represents the relationship between the working current and the optical power of the direct-modulated laser, the current-time curve represents the unidirectional envelope modulation signal after superimposing the first bias current signal, and the power-time curve represents the first RF optical signal. It can be seen that when the working current of the direct-modulated laser is less than or equal to the threshold current, the optical power obtained by the optical modulation of the direct-modulated laser is zero; for the case where the working current of the direct-modulated laser is greater than the threshold current, the greater the working current of the direct-modulated laser, the greater the optical power obtained by the optical modulation of the direct-modulated laser. Based on this characteristic of the direct-modulated laser, the unidirectional envelope modulation signal is superimposed with the first bias current signal whose corresponding current is greater than or equal to the threshold current of the direct-modulated laser and less than the first current, so that the working current of the direct-modulated laser is set according to the electrical signal after the superposition of the first bias current signal and the unidirectional envelope modulation signal, so that the direct-modulated laser can obtain the first RF optical signal by optical modulation.

[0219] The first current may be predefined or determined based on a predefined optical power (the first current may be the operating current required for the direct-modulated laser to perform optical modulation to obtain a predefined optical power). For example, the first current may be less than the bias current required for the direct-modulated laser to perform optical modulation on the first radio frequency electrical signal to obtain an optical signal having a complete waveform of the first radio frequency electrical signal. In addition, the current corresponding to the first bias current signal may be set to a low output optical power point (for example, a threshold current or near a threshold current), which is conducive to obtaining a first radio frequency optical signal with a lower average optical power, thereby more effectively reducing the power consumption of optical devices, and in a scenario where optical fiber is used to transmit optical signals between the first communication device and the second communication device, more effectively reducing the nonlinear effects of optical fiber transmission.

[0220] In embodiment 3.2, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator. In this case, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage. The upper envelope of the unidirectional envelope modulation signal used by the electro-absorption modulator or Mach-Zehnder modulator for optical modulation is flat, and the lower envelope corresponds to the lower envelope of the first RF electrical signal. When the DC component of the first RF electrical signal is zero, the electro-absorption modulator or Mach-Zehnder modulator can use a negative unidirectional envelope modulation signal for optical modulation.

[0221] In addition, in the scenario where the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, a laser diode can be additionally used to generate a light source, and the electro-absorption modulator or the Mach-Zehnder modulator realizes light modulation based on the light source generated by the laser diode. It can be seen that the light source generation and light modulation are realized by different devices, which is beneficial to reduce the influence of the light source bandwidth on high-frequency modulation when the voltage corresponding to the first bias voltage signal is low.

[0222] The following is a specific explanation using the example of the optical modulator being an electro-absorption modulator. The case where the optical modulator is a Mach-Zehnder modulator is similar to the case where the optical modulator is an electro-absorption modulator. Please refer to the relevant explanation of the optical modulator being an electro-absorption modulator and will not be repeated here.

[0223] Understandably, the first bias voltage signal applied to the electro-absorption modulator causes the electro-absorption modulator's bias voltage to be a voltage corresponding to the first bias voltage signal. The electro-absorption modulator optically modulates the unidirectional envelope modulated signal superimposed with the first bias voltage signal. Specifically, the electro-absorption modulator, with a bias voltage corresponding to the first bias voltage signal, optically modulates the unidirectional envelope modulated signal. During this optical modulation process, the electro-absorption modulator's operating voltage is set according to the unidirectional envelope modulated signal superimposed with the first bias voltage signal.

[0224] For example, taking the case where the DC component corresponding to the first radio frequency electrical signal is 0 as an example, in conjunction with FIG22 , in FIG22 , the power-voltage curve represents the relationship between the operating voltage and optical power of the electro-absorption modulator, the voltage-time curve represents the unidirectional envelope modulation signal after superimposing the first bias voltage signal, and the power-time curve represents the first radio frequency optical signal. It can be seen that the smaller the operating voltage of the electro-absorption modulator, the greater the optical power obtained by the electro-absorption modulator through optical modulation; the greater the operating voltage of the electro-absorption modulator, the smaller the optical power obtained by the electro-absorption modulator through optical modulation. Based on this characteristic of the electro-absorption modulator, the unidirectional envelope modulation signal is superimposed with the first bias voltage signal whose corresponding voltage is greater than the first voltage, so that the operating voltage of the electro-absorption modulator is set according to the unidirectional envelope modulation signal after superimposing the first bias voltage signal, so that the electro-absorption modulator can obtain the first radio frequency optical signal through optical modulation.

[0225] The first voltage may be predefined or determined based on a predefined optical power (the first voltage may be the operating voltage required by the electro-absorption modulator to perform optical modulation to obtain the predefined optical power). For example, the first voltage is greater than the middle voltage in the linear region of the power-voltage curve. Furthermore, the voltage corresponding to the first bias voltage signal may be set at a low output optical power point (high voltage), which facilitates obtaining a first RF optical signal with a lower average optical power, thereby more effectively reducing the power consumption of optical devices and, in scenarios where optical fiber is used to transmit optical signals between the first communication device and the second communication device, more effectively reducing the nonlinear effects of optical fiber transmission.

[0226] S103: The second communication device converts the first radio frequency optical signal into a first radio frequency electrical signal.

[0227] In an optional embodiment, the first RF electrical signal obtained by the second communication device from converting the first RF optical signal is a baseband signal within a unidirectional envelope modulated signal obtained by the second communication device through optoelectronic conversion of the first RF optical signal. The center frequency of the baseband signal is the same as the carrier frequency of the first RF electrical signal used by the first communication device to obtain the unidirectional envelope modulated signal. Optionally, the carrier frequency of the first RF electrical signal used by the first communication device to obtain the unidirectional envelope modulated signal may be the carrier frequency transmitted by the first communication device to the second communication device.

[0228] In one optional embodiment, the second communication device converts the first RF optical signal into the first RF electrical signal, which may include: the second communication device performing photoelectric conversion on the first RF optical signal using a photodetector to obtain a unidirectional envelope modulated signal, wherein the passband of the photodetector covers the spectrum of the baseband signal in the unidirectional envelope modulated signal; and the second communication device filtering the unidirectional envelope modulated signal using a bandpass filter to obtain the first RF electrical signal, wherein the passband of the bandpass filter only includes the spectrum of the baseband signal in the unidirectional envelope modulated signal. The photodetector may be, for example, a PD.

[0229] It can be seen that the second communication device can convert the first RF optical signal into the first RF electrical signal via a photodetector and a bandpass filter, eliminating the need for complex algorithmic processing and simplifying the method for recovering the first RF electrical signal. Furthermore, the bandpass filter's passband encompasses only the spectrum of the baseband signal in the unidirectional envelope modulated signal, indicating that the bandpass filter's passband encompasses only the RF spectrum of the baseband signal in the unidirectional envelope modulated signal. The photodetector's passband encompasses only the spectrum of the baseband signal in the unidirectional envelope modulated signal, as discussed later, is similar and will not be further discussed.

[0230] In another optional manner, the second communication device converts the first RF optical signal into the first RF electrical signal, which may include: the second communication device performs photoelectric conversion on the first RF optical signal through a photodetector to obtain a unidirectional envelope modulated signal, and determines the first RF electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector only contains the spectrum of the baseband signal. The photodetector may be a PD, for example. It can be seen that in addition to having the function of photoelectric conversion, the photodetector can also filter out the baseband signal in the unidirectional envelope modulated signal, thereby obtaining the first RF electrical signal. The second communication device can convert the first RF optical signal into the first RF electrical signal directly through a photodetector, without using complex algorithm processing, thereby simplifying the method of recovering the first RF electrical signal.

[0231] In summary, in this signal transmission method, the first communication device converts the first RF electrical signal into a unidirectional envelope modulated signal; the upper envelope and lower envelope of the first RF electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulated signal is a sine wave. The first communication device sends a first RF optical signal; the first RF optical signal is a unidirectional envelope RF optical signal obtained by optically modulating the unidirectional envelope modulated signal, and the lower envelope is flat, and the lower envelope amplitude is less than or equal to a first value. The second communication device converts the first RF optical signal into a first RF electrical signal. The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0232] It can be seen that compared with the optical signal with symmetrical upper and lower envelopes obtained by optically modulating the first RF electrical signal, the average optical power of the first RF optical signal obtained based on the unidirectional envelope modulation signal is lower, thereby reducing the transmission optical power between the first communication device and the second communication device, which is beneficial to reducing the power consumption of optical devices and improving power conversion efficiency.

[0233] For example, in a scenario where optical fiber is used to transmit optical signals between a second communication device and a first communication device, and the optical fiber transmission link between the first and second communication devices includes an optical amplifier, reducing the optical power transmitted between the second and first communication devices helps reduce the power consumption of the optical amplifier. Furthermore, reducing the optical power also helps reduce signal distortion caused by the optical amplifier easily entering a gain saturation region. For another example, in a scenario where the second communication device performs photoelectric conversion on a first radio frequency optical signal using a photodetector, reducing the optical power transmitted between the second and first communication devices helps reduce the DC current of the photodetector, thereby reducing the power consumption of the photodetector and improving the power conversion efficiency of the photodetector.

[0234] In scenarios where optical fiber is used to transmit optical signals between a second communication device and a first communication device, reducing the transmitted optical power can also help reduce the nonlinear effects of optical fiber transmission, thereby reducing signal distortion caused by these effects. In scenarios where the second communication device also needs to output a first RF electrical signal to an antenna for signal radiation, a first RF optical signal with a lower average optical power can also help keep the optical fiber's transmitted optical power below the power threshold that produces nonlinear effects in optical fiber transmission. Therefore, the range between the average optical power of the first RF optical signal and the power threshold can serve as a transmission optical power amplification factor, which can help reduce the nonlinear effects of optical fiber transmission while also obtaining an optical signal with a larger optical modulation amplitude, thereby improving the antenna's RF radiation power and signal quality.

[0235] In addition, the second communication device also restores the first RF optical signal with lower average optical power into a first RF electrical signal with higher power. In the scenario where the second communication device needs to output the first RF electrical signal to the antenna for signal radiation, this signal transmission method can achieve higher RF radiation power of the antenna with lower transmission optical power.

[0236] It is understandable that in order to implement the functions in the above method, the first communication device or the second communication device includes hardware structures and / or software modules corresponding to the execution of each function. It should be readily apparent to those skilled in the art that, in combination with the units and method steps of each example described in the embodiments disclosed in this application, this application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in hardware or in a computer software-driven hardware manner depends on the specific application scenario and design constraints of the technical solution.

[0237] The following describes possible structures of the first communication device and the second communication device provided in the embodiments of the present application in conjunction with the accompanying drawings.

[0238] Please refer to FIG. 23 , which is a schematic structural diagram of a first communication device 2300 provided in an embodiment of the present application. The first communication device 2300 includes a coupling module 2301 and an electro-optical conversion module 2302 .

[0239] Coupling module 2301 is configured to superimpose the first electrical signal on the first RF electrical signal to obtain a unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to electro-optical conversion module 2302. Electro-optical conversion module 2302 is configured to optically modulate the unidirectional envelope modulated signal to obtain a first RF optical signal. Electro-optical conversion module 2302 may also be configured to transmit the first RF optical signal.

[0240] The first RF electrical signal is determined based on the baseband signal, and the upper and lower envelopes of the first RF electrical signal are symmetrical with respect to the DC component. The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or alternatively, the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal. The first RF optical signal is a unidirectional envelope RF optical signal having a flat lower envelope and a lower envelope amplitude less than or equal to a first value.

[0241] The carrier in the unidirectional envelope modulated signal is a sine wave. The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal. Alternatively, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0242] In an optional embodiment, the electro-optical conversion module 2302 may be an optical modulator. The optical modulator optically modulates the unidirectional envelope modulated signal to obtain the first radio frequency optical signal. Specifically, the optical modulator may be configured to: superimpose a first bias electrical signal on the unidirectional envelope modulated signal; and optically modulate the unidirectional envelope modulated signal superimposed with the first bias electrical signal to obtain the first radio frequency optical signal.

[0243] Optionally, the optical modulator can be a directly modulated laser. In this case, the first bias electrical signal is a first bias current signal, the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0244] Optionally, the optical modulator may be an electro-absorption modulator or a Mach-Zehnder modulator. In this case, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0245] In an optional embodiment, the first communication device 2300 may further include a baseband module 2303, as shown in FIG24 . The baseband module 2303 may be configured to generate a first electrical signal and output the first electrical signal to the coupling module 2301. The baseband module 2303 may also be configured to generate a first radio frequency electrical signal and output the first radio frequency electrical signal to the coupling module 2301.

[0246] Optionally, the baseband module 2303 generates a first electrical signal and a first RF electrical signal, and can specifically be used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2303 to convert the baseband digital signal into a digital baseband modulated signal; perform digital-to-analog conversion on the digital envelope signal of the digital baseband modulated signal to obtain a first electrical signal as an analog signal; perform up-conversion processing on the digital baseband modulated signal to obtain a digital RF signal; and then perform digital-to-analog conversion on the digital RF signal to obtain the first RF electrical signal as an analog signal. In this embodiment of the present application, a digital-to-analog converter (DAC) can be used to implement digital-to-analog conversion, which will not be described in detail below.

[0247] In addition, the embodiment of the present application does not restrict the order of the operation of the baseband module 2303 performing digital-to-analog conversion on the digital envelope signal of the digital baseband modulated signal to obtain a first electrical signal as an analog signal, and the operation of the baseband module 2303 performing up-conversion processing on the digital baseband modulated signal to obtain a digital RF signal, and then performing digital-to-analog conversion on the digital RF signal to obtain a first RF electrical signal as an analog signal.

[0248] In another optional embodiment, the first communication device 2300 may further include a baseband module 2303 and an up-conversion module 2304, as shown in FIG25 . The baseband module 2303 may be configured to generate a first electrical signal and output the first electrical signal to the coupling module 2301. The baseband module 2303 may also be configured to generate a baseband signal (the baseband signal is an analog baseband signal) or an intermediate frequency signal corresponding to the baseband signal (the intermediate frequency signal is an analog signal), and output the baseband signal or the intermediate frequency signal to the up-conversion module 2304. The up-conversion module 2304 may be configured to perform up-conversion processing on the baseband signal or the intermediate frequency signal to obtain a first radio frequency electrical signal, and output the first radio frequency electrical signal to the coupling module 2301.

[0249] Optionally, the baseband module 2303 generates a first electrical signal and a baseband signal, which can be specifically used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2303 to convert the baseband digital signal into a digital baseband modulated signal; perform digital-to-analog conversion on the digital envelope signal of the digital baseband modulated signal to obtain a first electrical signal as an analog signal; and perform digital-to-analog conversion on the digital baseband modulated signal to obtain a baseband analog signal (i.e., the baseband signal in the analog domain). In addition, the embodiment of the present application does not limit the order of the operation of the baseband module 2303 performing digital-to-analog conversion on the digital envelope signal of the digital baseband modulated signal to obtain the first electrical signal as an analog signal and the operation of the baseband module 2303 performing digital-to-analog conversion on the digital baseband modulated signal to obtain the baseband analog signal.

[0250] Optionally, the baseband module 2303 generates an intermediate frequency signal corresponding to the first electrical signal and the baseband signal, which can be specifically used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2303 to convert the baseband digital signal into a digital baseband modulation signal; perform digital-to-analog conversion on the digital envelope signal of the digital baseband modulation signal to obtain a first electrical signal as an analog signal; perform up-conversion processing on the digital baseband modulation signal to obtain a digital intermediate frequency signal; and then perform digital-to-analog conversion on the digital intermediate frequency signal to obtain an intermediate frequency signal as an analog signal. In the embodiment of the present application, the order of the operation of the baseband module 2303 performing digital-to-analog conversion on the digital envelope signal of the digital baseband modulation signal to obtain the first electrical signal as an analog signal and the operation of the baseband module 2303 performing up-conversion processing on the digital baseband modulation signal to obtain the digital intermediate frequency signal and then performing digital-to-analog conversion on the digital intermediate frequency signal to obtain the intermediate frequency signal as an analog signal is not limited.

[0251] It can be seen that the first communication devices 2300 shown in Figures 24 and 25 can both obtain the first radio frequency optical signal based on the baseband digital signal input to the first communication device and output the first radio frequency optical signal, as shown in Figure 26.

[0252] In an optional embodiment, in the first communication device 2300 shown in Figure 24 or Figure 25, the baseband module 2303 can also be used to adjust the amplitude and delay of the generated first electrical signal through digital delay, and / or adjust the amplitude and delay of the generated first RF electrical signal / baseband signal / intermediate frequency signal, so that the first electrical signal is time-synchronized with the first RF electrical signal and the amplitude of the first electrical signal is the same as the envelope amplitude of the first RF electrical signal.

[0253] In an optional embodiment, in the first communication device 2300, the transmission branch for transmitting the first electrical signal and the transmission branch for transmitting the first RF electrical signal / baseband signal / intermediate frequency signal can be configured to ensure that the first electrical signal is time-synchronized with the first RF electrical signal and that the amplitude of the first electrical signal is the same as the envelope amplitude of the first RF electrical signal by adjusting the transmission line length and / or adding an amplifier, attenuator, and / or delay device. The amplifier can be used to amplify the signal, the attenuator can be used to attenuate the signal, and the delay device can be used to delay the signal.

[0254] For the detailed description of each module / device in Figures 23 to 25, please refer to the aforementioned related description, which will not be repeated here. In addition, the detailed description of each embodiment described above can also refer to the relevant description in the aforementioned signal transmission method. The first communication device 2300 shown in Figures 23 to 25 can also be used to implement the functions of the first communication device in the aforementioned signal transmission method, and also has corresponding beneficial effects, which will not be repeated here.

[0255] Please refer to Figure 27, which is a structural diagram of a first communication device 2700 provided in an embodiment of the present application. The first communication device 2700 includes a low-noise power amplifier 2701, a low-pass filter 2702 and an electro-optical conversion module 2703.

[0256] Low-noise power amplifier 2701 is used to convert the first RF electrical signal into a second RF electrical signal, and output the second RF electrical signal to low-pass filter 2702. Low-pass filter 2702 is used to filter the second RF electrical signal to obtain a baseband signal and a baseband signal in the second RF electrical signal. Low-pass filter 2702 is also used to adjust the spectral amplitude of the baseband signal and the baseband signal in the second RF electrical signal to obtain a unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to electro-optical conversion module 2703. Electro-optical conversion module 2703 is used to optically modulate the unidirectional envelope modulated signal to obtain a first RF optical signal. Electro-optical conversion module 2703 is also used to transmit the first RF optical signal.

[0257] The upper and lower envelopes of the first RF electrical signal are symmetrical relative to the DC component. The second RF electrical signal is a positive half-amplitude signal or a negative half-amplitude signal of the first RF electrical signal relative to the DC component. The first RF optical signal is a unidirectional RF optical signal with a flat lower envelope and a lower envelope amplitude less than or equal to a first value.

[0258] The carrier in the unidirectional envelope modulated signal is a sine wave. The unidirectional envelope modulated signal is composed of an adjusted baseband signal and an adjusted fundamental frequency signal. The difference between the amplitude of the baseband component and the amplitude of the fundamental frequency component in the spectrum corresponding to the unidirectional envelope modulated signal is less than or equal to a second value. The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; alternatively, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0259] In an optional embodiment, the low noise power amplifier 2701 can be a class B low noise power amplifier (e.g., class B LNA), a class AB low noise power amplifier (e.g., class AB LNA), or a class C low noise power amplifier (e.g., class C LNA).

[0260] In an optional embodiment, the electro-optical conversion module 2703 may be an optical modulator. The optical modulator optically modulates the unidirectional envelope modulated signal to obtain a first radio frequency optical signal. Specifically, the optical modulator may be configured to: superimpose a first bias electrical signal on the unidirectional envelope modulated signal; and optically modulate the unidirectional envelope modulated signal superimposed with the first bias electrical signal to obtain the first radio frequency optical signal.

[0261] Optionally, the optical modulator can be a directly modulated laser. In this case, the first bias electrical signal is a first bias current signal, the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0262] Optionally, the optical modulator may be an electro-absorption modulator or a Mach-Zehnder modulator. In this case, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0263] In an optional embodiment, the first communication device 2700 may further include a baseband module 2704, as shown in FIG28 . The baseband module 2704 may be used to generate a first radio frequency electrical signal and output the first radio frequency electrical signal to the low noise power amplifier 2701. Optionally, the first radio frequency electrical signal of the baseband module 2704 may be specifically used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2704 to convert the baseband digital signal into a digital baseband modulated signal; perform up-conversion processing on the digital baseband modulated signal to obtain a digital radio frequency signal; and then perform digital-to-analog conversion on the digital radio frequency signal to obtain the first radio frequency electrical signal as an analog signal.

[0264] In another optional embodiment, the first communication device 2700 may further include a baseband module 2704 and an up-conversion module 2705, as shown in FIG29 . The baseband module 2704 may be used to generate a baseband signal (the baseband signal is a baseband signal in the analog domain) or an intermediate frequency signal (the intermediate frequency signal is an analog signal) corresponding to the baseband signal, and output the baseband signal or the intermediate frequency signal to the up-conversion module 2705. The up-conversion module 2705 may be used to perform up-conversion processing on the baseband signal or the intermediate frequency signal to obtain a first radio frequency electrical signal, and output the first radio frequency electrical signal to the low noise power amplifier 2701.

[0265] Optionally, the baseband module 2704 generates a baseband signal, which can be specifically used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2704 to convert the baseband digital signal into a digital baseband modulated signal; perform digital-to-analog conversion on the digital baseband modulated signal to obtain a baseband analog signal (i.e., the baseband signal in the analog domain).

[0266] Optionally, the baseband module 2704 generates an intermediate frequency signal corresponding to the baseband signal, which can be specifically used to: modulate the baseband digital signal (i.e., the baseband signal in the digital domain) input to the baseband module 2704 to convert the baseband digital signal into a digital baseband modulated signal; perform up-conversion processing on the digital baseband modulated signal to obtain a digital intermediate frequency signal; and then perform digital-to-analog conversion on the digital intermediate frequency signal to obtain an intermediate frequency signal as an analog signal.

[0267] It can be seen that the first communication devices 2700 shown in Figures 28 and 29 can both obtain the first radio frequency optical signal based on the baseband digital signal input to the first communication device and output the first radio frequency optical signal, as shown in Figure 26.

[0268] In another optional embodiment, the first communication device 2300 may further include an antenna configured to receive the first radio frequency electrical signal. This embodiment may be applied to a scenario where the first communication device is an RRH or is deployed in an RRH and the second communication device is a BBU or is deployed in a BBU.

[0269] For the detailed description of each module / device in Figures 27 to 29, please refer to the aforementioned related description, which will not be repeated here. In addition, the detailed description of each embodiment described above can also refer to the relevant description in the aforementioned signal transmission method. The first communication device 2700 shown in Figures 27 to 29 can also be used to implement the functions of the first communication device in the aforementioned signal transmission method, and also has corresponding beneficial effects, which will not be repeated here.

[0270] Please refer to FIG. 30 , which is a schematic structural diagram of a second communication device 3000 provided in an embodiment of the present application. The second communication device 3000 includes a photodetector 3001 and a bandpass filter 3002 .

[0271] Photodetector 3001 is configured to receive a first RF optical signal. Photodetector 3001 is also configured to perform photoelectric conversion on the first RF optical signal to obtain a unidirectional envelope modulated signal, which is then output to bandpass filter 3002. The passband of photodetector 3001 covers the spectrum of the baseband signal in the unidirectional envelope modulated signal. Bandpass filter 3002 is configured to filter the unidirectional envelope modulated signal to obtain a first RF electrical signal. The passband of bandpass filter 3002 only includes the spectrum of the baseband signal in the unidirectional envelope modulated signal.

[0272] Please refer to Figure 31, which is a schematic diagram of the structure of a second communication device 3100 provided in an embodiment of the present application. The second communication device 3100 includes a photodetector 3101. The photodetector 3101 is used to receive a first radio frequency optical signal; the photodetector 3101 is also used to perform photoelectric conversion on the first radio frequency optical signal to obtain a unidirectional envelope modulated signal, and to determine the first radio frequency electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector 3101 only includes the spectrum of the baseband signal in the unidirectional envelope modulated signal.

[0273] It can be seen that the second communication devices shown in Figures 30 and 31 can both be used to restore the first RF optical signal input into the second communication device into a first RF electrical signal and output the first RF electrical signal, as shown in Figure 32.

[0274] In an optional implementation, the second communication device 3000 shown in FIG. 30 or the second communication device 3100 shown in FIG. 31 may further include an antenna, and the antenna is configured to radiate a signal based on the first radio frequency electrical signal.

[0275] In addition, the second communication device shown in Figures 30 and 31 can be used to implement the function of the second communication device in the aforementioned signal transmission method, and also has corresponding beneficial effects. For detailed description, please refer to the aforementioned related description, and will not be repeated here.

[0276] In addition to having the structure shown in any one of Figures 23 to 25 and Figures 27 to 29, the first communication device may have the structure shown in any one of Figures 30 or 31, and the second communication device may also have the structure shown in any one of Figures 33 to 35.

[0277] As shown in Figure 33, an embodiment of the present application provides a communication device 3300. The communication device 3300 can be a first communication device or a second communication device; the communication device 3300 can also be a component of the first communication device (for example, an integrated circuit, a chip, etc.), or a component of the second communication device (for example, an integrated circuit, a chip, etc.), used to implement the method in the method embodiment of the present application. The communication device 3300 may include: a communication unit 3301 and a processing unit 3302. Among them, the processing unit 3302 is used to control the communication unit 3301 to send and receive data / signaling. Optionally, the communication device 3300 may also include a storage unit 3303.

[0278] In one possible design, the communication device 3300 is used to implement the function of the first communication device in the embodiment of the present application:

[0279] The processing unit 3302 is used to convert the first radio frequency electrical signal into a unidirectional envelope modulated signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0280] The communication unit 3301 is used to send a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, with a flat lower envelope and a lower envelope amplitude less than or equal to a first value.

[0281] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0282] In an optional embodiment, the first RF electrical signal is determined based on a baseband signal. The processing unit 3302 converts the first RF electrical signal into a unidirectional envelope modulated signal, specifically for determining the unidirectional envelope modulated signal based on the first RF electrical signal and the first electrical signal, wherein the first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting the baseband amplitude signal corresponding to the baseband signal.

[0283] In an optional implementation, the processing unit 3302 determines the unidirectional envelope modulation signal according to the first RF electrical signal and the first electrical signal, and is specifically configured to: superimpose the first electrical signal on the first RF electrical signal to obtain the unidirectional envelope modulation signal.

[0284] In an optional embodiment, the first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

[0285] In an optional embodiment, the processing unit 3302 converts the first RF electrical signal into a unidirectional envelope modulated signal, specifically for: converting the first RF electrical signal into a second RF electrical signal, where the second RF electrical signal is a positive half-amplitude signal or a negative half-amplitude signal of the first RF electrical signal relative to a DC component; filtering the second RF electrical signal to obtain a baseband signal and a baseband signal in the second RF electrical signal; and adjusting the amplitudes of the baseband signal and the baseband signal in the frequency spectrum to obtain a unidirectional envelope modulated signal. The unidirectional envelope modulated signal is composed of the adjusted baseband signal and the adjusted baseband signal; and the difference between the amplitude of the baseband component and the amplitude of the baseband component in the frequency spectrum corresponding to the unidirectional envelope modulated signal is less than or equal to the second value.

[0286] In an optional embodiment, the processing unit 3302 is further used to superimpose a first bias electrical signal on the unidirectional envelope modulated signal through an optical modulator; the processing unit 3302 is further used to optically modulate the unidirectional envelope modulated signal after superimposing the first bias electrical signal through an optical modulator to obtain a first RF optical signal.

[0287] In an optional embodiment, the optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; the current corresponding to the first bias current signal is greater than or equal to the threshold current of the directly modulated laser, and the current corresponding to the first bias current signal is less than the first current.

[0288] In an optional implementation, the optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, and the first bias electrical signal is a first bias voltage signal; the voltage corresponding to the first bias voltage signal is greater than the first voltage.

[0289] In an optional implementation, the processing unit 3302 is further configured to generate a first radio frequency electrical signal.

[0290] In another possible design, the communication device 3300 is used to implement the function of the second communication device in the embodiment of the present application:

[0291] The communication unit 3301 is used to receive a first RF optical signal; the first RF optical signal is a unidirectional envelope RF optical signal obtained by optically modulating a unidirectional envelope modulated signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulated signal is a sine wave.

[0292] The processing unit 3302 is configured to convert the first radio frequency optical signal into a first radio frequency electrical signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component.

[0293] In which, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

[0294] In an optional implementation, the first radio frequency electrical signal obtained by converting the first radio frequency optical signal is a baseband signal in a unidirectional envelope modulated signal obtained by performing photoelectric conversion on the first radio frequency optical signal.

[0295] In an optional embodiment, the processing unit 3302 converts the first RF optical signal into a first RF electrical signal, specifically for: performing photoelectric conversion on the first RF optical signal through a photodetector to obtain a unidirectional envelope modulated signal; the passband of the photodetector covers the spectrum of the baseband signal; and filtering the unidirectional envelope modulated signal through a bandpass filter to obtain the first RF electrical signal; the passband of the bandpass filter only contains the spectrum of the baseband signal.

[0296] In an optional embodiment, the processing unit 3302 converts the first RF optical signal into a first RF electrical signal, specifically for: performing photoelectric conversion on the first RF optical signal through a photodetector to obtain a unidirectional envelope modulated signal, and determining the first RF electrical signal from the unidirectional envelope modulated signal; the passband of the photodetector only contains the spectrum of the baseband signal.

[0297] In yet another possible design, the communication device 3300 is used to implement the function of the first communication device 2300 shown in any one of FIG. 23 to FIG. 25 :

[0298] The processing unit 3302 may have the functions of the coupling module 2301 and other functions of the electrical-optical conversion module 2302 except sending the first radio frequency optical signal, and the communication unit 3301 may have the function of the electrical-optical conversion module 2302 sending the first radio frequency optical signal.

[0299] When the communication device 3300 is used to implement the functions of the first communication device 2300 shown in Figure 24, the processing unit 3302 may also have the functions of the baseband module 2303 in the first communication device 2300 shown in Figure 24. When the communication device 3300 is used to implement the functions of the first communication device 2300 shown in Figure 25, the processing unit 3302 may also have the functions of the baseband module 2303 and the up-conversion module 2304 in the first communication device 2300 shown in Figure 25.

[0300] In yet another possible design, the communication device 3300 is used to implement the function of the first communication device 2700 shown in any one of FIG. 27 to FIG. 29 :

[0301] The processing unit 3302 can have the function of the low noise power amplifier 2701, the function of the low-pass filter 2702, and other functions of the electro-optical conversion module 2703 except sending the first radio frequency optical signal, and the communication unit 3301 can have the function of the electro-optical conversion module 2703 sending the first radio frequency optical signal.

[0302] When the communication device 3300 is used to implement the functions of the first communication device 2700 shown in FIG28 , the processing unit 3302 may also have the functions of the baseband module 2704 in the first communication device 2700 shown in FIG28 . When the communication device 3300 is used to implement the functions of the first communication device 2700 shown in FIG29 , the processing unit 3302 may also have the functions of the baseband module 2704 and the up-conversion module 2705 in the first communication device 2700 shown in FIG29 .

[0303] In yet another possible design, the communication device 3300 is used to implement the functions of the second communication device 3000 shown in FIG. 30 :

[0304] The communication unit 3301 may have the function of the photodetector 3001 to receive the first radio frequency optical signal, and the processing unit 3302 may have other functions of the photodetector 3001 except receiving the first radio frequency optical signal and the function of the bandpass filter 3002 .

[0305] In yet another possible design, the communication device 3300 is used to implement the functions of the second communication device 3100 shown in FIG. 31 :

[0306] The communication unit 3301 may have the function of the photodetector 3101 to receive the first radio frequency optical signal, and the processing unit 3302 may have other functions of the photodetector 3101 except receiving the first radio frequency optical signal.

[0307] The embodiments of the present application and the above-mentioned method embodiments are based on the same concept, and the technical effects they bring are also the same. For the specific principles, please refer to the description of the above-mentioned embodiments, which will not be repeated here.

[0308] The present application also provides a communication device 3400, as shown in Figure 34. The communication device 3400 can be a first communication device or a second communication device, or can be a chip, chip system, or processor that supports the first communication device to implement the above method, or can be a chip, chip system, or processor that supports the second communication device to implement the above method. This device can be used to implement the method described in the above method embodiment. For details, please refer to the description of the above method embodiment.

[0309] The communication device 3400 may include a processor 3401. The processor 3401 may be a general-purpose processor or a dedicated processor. The processor 3401 may be, for example, a baseband processor, a digital signal processor, an application-specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or a central processing unit (CPU). The baseband processor may be used to process communication protocols and communication data, and the central processing unit may be used to control a communication device (such as a base station, a baseband chip, a terminal, a terminal chip, a DU or CU, etc.), execute software programs, and process data from the software programs. The communication device 3400 may also include a transceiver 3402. The transceiver 3402 may include a communication interface, or the transceiver 3402 may include a communication interface and a radio frequency processing module; the communication interface may be an input / output interface or an input interface or an output interface. The communication device 3400 may also include a memory 3403.

[0310] For example, in one possible design, the communication device 3400 is used to implement the function of the first communication device 2300 shown in any one of Figures 23 to 25 in the embodiments of the present application:

[0311] The transceiver 3402 may include a communication interface, which may have the functions of the coupling module 2301 and the electrical-to-optical conversion module 2302 .

[0312] When the communication device 3400 is used to implement the functions of the first communication device 2300 shown in FIG. 24 , the processor 3401 may have the functions of the baseband module 2303 in the first communication device 2300 shown in FIG. 24 .

[0313] When the communication device 3400 is used to implement the functions of the first communication device 2300 shown in Figure 25, the processor 3401 may have the functions of the baseband module 2303 in the first communication device 2300 shown in Figure 25, and the transceiver 3402 may also include a radio frequency processing module, which may have the functions of the up-conversion module 2304 in the first communication device 2300 shown in Figure 25.

[0314] In another possible design, the communication device 3400 is used to implement the function of the first communication device 2700 shown in any one of Figures 27 to 29 in the embodiments of the present application:

[0315] The transceiver 3402 may include a radio frequency processing module and a communication interface. The radio frequency processing module may have the functions of a low noise power amplifier 2701 and a low pass filter 2702 , and the communication interface may have the function of an electro-optical conversion module 2703 .

[0316] When the communication device 3400 is used to implement the functions of the first communication device 2700 shown in FIG. 28 , the processor 3401 may have the functions of the baseband module 2704 in the first communication device 2700 shown in FIG. 28 .

[0317] When the communication device 3400 is used to implement the functions of the first communication device 2700 shown in Figure 29, the processor 3401 may have the functions of the baseband module 2303 in the first communication device 2700 shown in Figure 29, and the RF processing module in the transceiver 3402 may also have the functions of the up-conversion module 2705 in the first communication device 2700 shown in Figure 29.

[0318] In another possible design, the communication device 3400 is used to implement the functions of the second communication device 3000 shown in Figure 30 in the embodiment of the present application: the transceiver 3402 may include a communication interface and a radio frequency processing module, the communication interface may have the function of the photodetector 3001, and the radio frequency processing module may have the function of the bandpass filter 3002.

[0319] In another possible design, the communication device 3400 is used to implement the functions of the second communication device 3100 shown in Figure 31 in the embodiment of the present application: the transceiver 3402 may include a communication interface, and the communication interface may have the function of the photodetector 3101.

[0320] The present application also provides a communication device 3500, as shown in FIG35 . The communication device 3500 may include a transceiver 3501 and an antenna 3502. The communication device 3500 may have the functions of the first communication device or the second communication device in the above method embodiment and may be used to implement the method described in the above method embodiment. For details, please refer to the description of the above method embodiment.

[0321] For example, in one possible design, the communication device 3500 is used to implement the functions of the first communication device 2700 shown in FIG. 27 in an embodiment of the present application:

[0322] Antenna 3502 can be used to receive a first RF electrical signal. Transceiver 3501 may include a RF processing module and a communication interface. Antenna 3502 may be connected to the RF processing module. The RF processing module may function as a low-noise power amplifier 2701, configured to convert the first RF electrical signal received by antenna 3502 into a second RF electrical signal. The RF processing module may also function as a low-pass filter 2702. The communication interface may function as an electro-optical conversion module 2703.

[0323] In another possible design, the communication device 3500 is used to implement the functions of the second communication device 3000 shown in Figure 30 in the embodiment of the present application: the transceiver 3501 may include a communication interface and a radio frequency processing module. The communication interface may have the function of the photodetector 3001, and the radio frequency processing module may have the function of the bandpass filter 3002. The transceiver 3501 may also be used to output the obtained first radio frequency electrical signal to the antenna 3502. The antenna 3502 may be used to radiate a signal based on the first radio frequency electrical signal.

[0324] In another possible design, the communication device 3500 is used to implement the functions of the second communication device 3100 shown in Figure 31 in the embodiment of the present application: the transceiver 3501 may include a communication interface, and the communication interface may have the function of the photodetector 3101. The transceiver 3501 may also be used to output the obtained first radio frequency electrical signal to the antenna 3502. The antenna 3502 may be used to radiate a signal based on the first radio frequency electrical signal.

[0325] In addition, the communication device 3500 may further include a processor 3503, on which instructions 3504 may be stored. The instructions 3504 can be executed to enable the communication device 3500 to perform the method described in the above method embodiment. The instructions 3504 may be fixed in the processor 3503. In this case, the processor 3503 may be implemented by hardware.

[0326] Optionally, the communication device 3500 may include one or more memories 3505, on which instructions 3506 may be stored. The instructions may be executed to cause the communication device 3500 to perform the method described in the above method embodiment. Optionally, the memory 3505 may also store data. The processor 3503 and the memory 3505 may be provided separately or integrated together.

[0327] Memory 3505 may include, but is not limited to, non-volatile memory such as a hard disk drive (HDD) or a solid-state drive (SSD), random access memory (RAM), erasable programmable ROM (EPROM), ROM or portable read-only memory (CD-ROM), etc.

[0328] Optionally, the communication device 3400 or the communication device 3500 may further include a circuit that can implement the function of sending or receiving or communicating in the aforementioned method embodiment. The processor and transceiver described in the embodiments of the present application can be implemented in an integrated circuit (integrated circuit, IC), an analog IC, a radio frequency integrated circuit (radio frequency integrated circuit, RFIC), a mixed signal IC, an application specific integrated circuit (application specific integrated circuit, ASIC), a printed circuit board (printed circuit board, PCB), an electronic device, etc. The processor and transceiver can also be manufactured using various IC process technologies, such as complementary metal oxide semiconductor (CMOS), N-type metal oxide semiconductor (nMetal-oxide-semiconductor, NMOS), P-type metal oxide semiconductor (positive channel metal oxide semiconductor, PMOS), bipolar junction transistor (bipolar junction transistor, BJT), bipolar CMOS (BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), etc.

[0329] The embodiment of the present application and the above-mentioned signal transmission method are based on the same concept, and the technical effects they bring are also the same. For the specific principles, please refer to the description in the above-mentioned signal transmission method, which will not be repeated here.

[0330] Those skilled in the art will also appreciate that the various illustrative logical blocks and steps listed in the embodiments of the present application can be implemented by electronic hardware, computer software, or a combination of both. Whether such functions are implemented by hardware or software depends on the specific application and the design requirements of the entire system. Those skilled in the art may use various methods to implement the described functions for each specific application, but such implementation should not be construed as exceeding the scope of protection of the embodiments of the present application.

[0331] The present application also provides a computer-readable storage medium for storing computer software instructions, which, when executed by a communication device, implements the functions of any of the above method embodiments.

[0332] The present application also provides a computer program product for storing computer software instructions, which, when executed by a communication device, implements the functions of any of the above method embodiments.

[0333] The present application also provides a computer program that, when executed on a computer, implements the functions of any of the above method embodiments.

[0334] The present application also provides a communication system, which includes the first communication device and the second communication device of the above aspect. In another possible design, the system may also include other devices that interact with the first communication device and / or the second communication device in the solution provided by the present application.

[0335] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, an SSD).

[0336] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0337] In the various embodiments of the present application, unless otherwise specified or there is a logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0338] In this application, "at least one" means one or more, and "more" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. In the text description of this application, the character " / " generally indicates that the previous and next related objects are in an "or" relationship; in the formulas of this application, the character " / " indicates that the previous and next related objects are in a "division" relationship.

[0339] It is understood that the various numbers used in the embodiments of this application are merely for ease of description and are not intended to limit the scope of the embodiments of this application. The order of the sequence numbers of the above-mentioned processes does not necessarily imply a specific order of execution; the order of execution of the processes should be determined by their functions and inherent logic.

Claims

1. A signal transmission method, characterized in that: The method comprises: Converting a first radio frequency electrical signal into a unidirectional envelope modulation signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to a DC component, and the carrier in the unidirectional envelope modulation signal is a sine wave; Sending a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating the unidirectional envelope modulation signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

2. The method according to claim 1, characterized in that The first radio frequency electrical signal is determined according to the baseband signal; and the converting the first radio frequency electrical signal into a unidirectional envelope modulation signal comprises: Determining the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal; The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal.

3. The method according to claim 2, characterized in that The step of determining the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal comprises: The first electrical signal is superimposed on the first radio frequency electrical signal to obtain the unidirectional envelope modulated signal.

4. The method according to claim 2 or 3, characterized in that: The first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

5. The method according to claim 1, characterized in that The step of converting the first radio frequency electrical signal into a unidirectional envelope modulation signal comprises: Converting the first radio frequency electrical signal into a second radio frequency electrical signal, wherein the second radio frequency electrical signal is a positive half amplitude signal or a negative half amplitude signal of the first radio frequency electrical signal relative to a DC component; filtering the second radio frequency electrical signal to obtain a baseband signal and a basefrequency signal in the second radio frequency electrical signal; Adjusting the amplitudes of the baseband signal and the baseband signal on the frequency spectrum to obtain the unidirectional envelope modulation signal; The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal; the difference between the amplitude of the baseband component and the amplitude of the baseband component in the spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value.

6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: superimposing a first bias electrical signal on the unidirectional envelope modulation signal through an optical modulator; The unidirectional envelope modulation signal superimposed with the first bias electrical signal is optically modulated by the optical modulator to obtain the first radio frequency optical signal.

7. The method according to claim 6, characterized in that The optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; The current corresponding to the first bias current signal is greater than or equal to the threshold current of the direct-modulated laser, and the current corresponding to the first bias current signal is less than the first current.

8. The method according to claim 6, characterized in that The optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

9. The method according to any one of claims 1 to 8, characterized in that: The method further comprises: The first radio frequency electrical signal is generated.

10. A signal transmission method, characterized in that: The method comprises: Receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, the lower envelope is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulation signal is a sine wave; converting the first radio frequency optical signal into a first radio frequency electrical signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to a DC component; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

11. The method according to claim 10, characterized in that The first radio frequency electrical signal obtained by converting the first radio frequency optical signal is: a baseband signal in the unidirectional envelope modulated signal obtained by performing photoelectric conversion on the first radio frequency optical signal.

12. The method according to claim 11, characterized in that The converting the first radio frequency optical signal into the first radio frequency electrical signal comprises: Performing photoelectric conversion on the first radio frequency optical signal through a photoelectric detector to obtain the unidirectional envelope modulation signal; the passband of the photoelectric detector covers the spectrum of the baseband signal; The unidirectional envelope modulated signal is filtered through a bandpass filter to obtain the first radio frequency electrical signal; the passband of the bandpass filter only contains the frequency spectrum of the baseband signal.

13. The method according to claim 11, characterized in that The converting the first radio frequency optical signal into the first radio frequency electrical signal comprises: The first radio frequency optical signal is photoelectrically converted by a photoelectric detector to obtain the unidirectional envelope modulated signal, and the first radio frequency electrical signal is determined from the unidirectional envelope modulated signal; the passband of the photoelectric detector only includes the spectrum of the baseband signal.

14. A signal transmission method, characterized in that: The method comprises: The first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulation signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component, and the carrier in the unidirectional envelope modulation signal is a sine wave; The first communication device sends a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating the unidirectional envelope modulation signal, the lower envelope being flat and the lower envelope amplitude being less than or equal to a first value; A second communication device receives the first radio frequency optical signal; The second communication device converts the first radio frequency optical signal into the first radio frequency electrical signal; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

15. The method according to claim 14, characterized in that The first radio frequency electrical signal is determined according to the baseband signal; the first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulation signal, including: The first communication device determines the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal; The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal.

16. The method according to claim 15, characterized in that The first communication device determines the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal, including: The first communication device superimposes the first electrical signal on the first radio frequency electrical signal to obtain the unidirectional envelope modulated signal.

17. The method according to claim 15 or 16, characterized in that The first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

18. The method according to claim 14, characterized in that The first communication device converts the first radio frequency electrical signal into a unidirectional envelope modulation signal, including: The first communication device converts the first radio frequency electrical signal into a second radio frequency electrical signal, where the second radio frequency electrical signal is a positive half amplitude signal or a negative half amplitude signal of the first radio frequency electrical signal relative to a DC component; The first communication device filters the second radio frequency electrical signal to obtain a baseband signal and a base frequency signal in the second radio frequency electrical signal; The first communication device adjusts the amplitude of the baseband signal and the baseband signal on the frequency spectrum to obtain the unidirectional envelope modulation signal; The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal; the difference between the amplitude of the baseband component and the amplitude of the baseband component in the spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value.

19. The method according to any one of claims 14 to 18, characterized in that The method further comprises: The first communication device superimposes a first bias electrical signal on the unidirectional envelope modulation signal through an optical modulator; The first communication device optically modulates the unidirectional envelope modulation signal superimposed with the first bias electrical signal through the optical modulator to obtain the first radio frequency optical signal.

20. The method according to claim 19, characterized in that The optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; The current corresponding to the first bias current signal is greater than or equal to the threshold current of the direct-modulated laser, and the current corresponding to the first bias current signal is less than the first current.

21. The method according to claim 19, characterized in that The optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

22. The method according to any one of claims 14 to 21, characterized in that The method further comprises: The first communication device generates the first radio frequency electrical signal.

23. The method according to any one of claims 14 to 22, characterized in that The first radio frequency electrical signal obtained by the second communication device converting the first radio frequency optical signal is: the baseband signal in the unidirectional envelope modulated signal obtained by the second communication device performing photoelectric conversion on the first radio frequency optical signal.

24. The method according to claim 23, characterized in that The second communication device converts the first radio frequency optical signal into the first radio frequency electrical signal, including: The second communication device performs photoelectric conversion on the first radio frequency optical signal through a photoelectric detector to obtain the one-way envelope modulation signal; the passband of the photoelectric detector covers the spectrum of the baseband signal in the one-way envelope modulation signal; The second communication device filters the unidirectional envelope modulated signal through a bandpass filter to obtain the first radio frequency electrical signal; the passband of the bandpass filter only includes the frequency spectrum of the baseband signal in the unidirectional envelope modulated signal.

25. The method according to claim 23, characterized in that The second communication device converts the first radio frequency optical signal into the first radio frequency electrical signal, including: The second communication device performs photoelectric conversion on the first radio frequency optical signal through a photoelectric detector to obtain the one-way envelope modulation signal, and determines the first radio frequency electrical signal from the one-way envelope modulation signal; the passband of the photoelectric detector only includes the spectrum of the baseband signal in the one-way envelope modulation signal.

26. A communication device, characterized in that: The communication device comprises: The coupling module is used to superimpose the first electrical signal on the first radio frequency electrical signal to obtain a unidirectional envelope modulation signal, and output the unidirectional envelope modulation signal to the optical modulator; the first radio frequency electrical signal is determined according to the baseband signal, and the upper envelope and the lower envelope of the first radio frequency electrical signal are The network is symmetrical with respect to the DC component; the carrier in the unidirectional envelope modulation signal is a sine wave; The optical modulator is used to optically modulate the unidirectional envelope modulation signal to obtain a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal with a flat lower envelope and a lower envelope amplitude less than or equal to a first value; The optical modulator is further used to send the first radio frequency optical signal; The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal; The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

27. The device according to claim 26, characterized in that The first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

28. The device according to claim 26 or 27, characterized in that The optical modulator optically modulates the unidirectional envelope modulation signal to obtain a first radio frequency electrical signal, which is specifically used for: superimposing a first bias electrical signal on the unidirectional envelope modulation signal; The unidirectional envelope modulated signal superimposed with the first bias electrical signal is optically modulated to obtain the first radio frequency optical signal.

29. The device according to claim 28, characterized in that The optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; The current corresponding to the first bias current signal is greater than or equal to the threshold current of the direct-modulated laser, and the current corresponding to the first bias current signal is less than the first current.

30. The device according to claim 28, characterized in that The optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

31. The device according to any one of claims 26 to 30, characterized in that The device also includes: a baseband module, configured to generate the first electrical signal and output the first electrical signal to the coupling module; The baseband module is further configured to generate the first radio frequency electrical signal and output the first radio frequency electrical signal to the coupling module.

32. The device according to any one of claims 26 to 30, characterized in that The device also includes: a baseband module, configured to generate the first electrical signal and output the first electrical signal to the coupling module; The baseband module is further used to generate the baseband signal or an intermediate frequency signal corresponding to the baseband signal, and output the baseband signal or the intermediate frequency signal corresponding to the baseband signal to the up-conversion module; The up-conversion module is used to up-convert the baseband signal or the intermediate frequency signal corresponding to the baseband signal to obtain the first radio frequency electrical signal, and output the first radio frequency electrical signal to the coupling module.

33. A communication device, characterized in that: The device comprises: A low-noise power amplifier, configured to convert a first radio frequency electrical signal into a second radio frequency electrical signal, and output the second radio frequency electrical signal to a low-pass filter; an upper envelope and a lower envelope of the first radio frequency electrical signal are symmetrical with respect to a DC component, and the second radio frequency electrical signal is a positive half amplitude signal or a negative half amplitude signal of the first radio frequency electrical signal with respect to the DC component; The low-pass filter is used to: filter the second radio frequency electrical signal to obtain a baseband signal and a baseband signal in the second radio frequency electrical signal; adjust the amplitude of the baseband signal and the baseband signal on the spectrum to obtain a unidirectional envelope modulation signal, and output the unidirectional envelope modulation signal to the optical modulator; the carrier in the unidirectional envelope modulation signal is a sine wave; The optical modulator is used to optically modulate the unidirectional envelope modulation signal to obtain a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal with a flat lower envelope and a lower envelope amplitude less than or equal to a first value; The optical modulator is further used to send the first radio frequency optical signal; The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal, and the difference between the amplitude of the baseband component and the amplitude of the baseband component in the frequency spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value; The unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

34. The device according to claim 33, characterized in that The low noise power amplifier is a class B low noise power amplifier, or a class AB low noise power amplifier, or a class C low noise power amplifier.

35. The device according to claim 33 or 34, characterized in that The optical modulator optically modulates the unidirectional envelope modulation signal to obtain a first radio frequency optical signal, which is specifically used for: superimposing a first bias electrical signal on the unidirectional envelope modulation signal; The unidirectional envelope modulated signal superimposed with the first bias electrical signal is optically modulated to obtain the first radio frequency optical signal.

36. The device according to claim 35, characterized in that The optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; The current corresponding to the first bias current signal is greater than or equal to the threshold current of the direct-modulated laser, and the current corresponding to the first bias current signal is less than the first current.

37. The device according to claim 35, characterized in that The optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

38. The device according to any one of claims 33 to 37, characterized in that The device also includes: The baseband module is used to generate the first radio frequency electrical signal and output the first radio frequency electrical signal to the low noise power amplifier.

39. The device according to any one of claims 33 to 37, characterized in that The device also includes: A baseband module, used to generate the baseband signal or an intermediate frequency signal corresponding to the baseband signal, and output the baseband signal or the intermediate frequency signal corresponding to the baseband signal to an up-conversion module; The up-conversion module is used to up-convert the baseband signal or the intermediate frequency signal corresponding to the baseband signal to obtain the first radio frequency electrical signal, and output the first radio frequency electrical signal to the low noise power amplifier.

40. A communication device, characterized in that: The device comprises: a photoelectric detector, configured to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulation signal is a sine wave; The photoelectric detector is further used to perform photoelectric conversion on the first radio frequency optical signal to obtain the unidirectional envelope modulated signal, and output the unidirectional envelope modulated signal to a bandpass filter; the passband of the photoelectric detector covers the spectrum of the baseband signal in the unidirectional envelope modulated signal; The bandpass filter is used to filter the unidirectional envelope modulated signal to obtain the first radio frequency electrical signal; the passband of the bandpass filter only contains the spectrum of the baseband signal in the unidirectional envelope modulated signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

41. A communication device, characterized in that: The device comprises: A photoelectric detector is used to receive a first radio frequency optical signal; the first radio frequency optical signal is obtained by optically modulating a unidirectional envelope modulation signal a unidirectional envelope radio frequency optical signal with a flat lower envelope and a lower envelope amplitude less than or equal to a first value, wherein the carrier in the unidirectional envelope modulated signal is a sine wave; The photodetector is further used to perform photoelectric conversion on the first radio frequency optical signal to obtain the one-way envelope modulation signal, and determine the first radio frequency electrical signal from the one-way envelope modulation signal; the passband of the photodetector only includes the spectrum of the baseband signal in the one-way envelope modulation signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to the DC component; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

42. A communication device, characterized in that: The device comprises: A processing unit, configured to convert a first radio frequency electrical signal into a unidirectional envelope modulation signal; the upper envelope and the lower envelope of the first radio frequency electrical signal are symmetrical with respect to a DC component, and the carrier in the unidirectional envelope modulation signal is a sine wave; A communication unit, configured to send a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating the unidirectional envelope modulation signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

43. The device according to claim 42, characterized in that The first radio frequency electrical signal is determined according to the baseband signal; the processing unit converts the first radio frequency electrical signal into a unidirectional envelope modulation signal, specifically for: Determining the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal; The first electrical signal is a baseband amplitude signal corresponding to the baseband signal, or the first electrical signal is an electrical signal obtained by inverting a baseband amplitude signal corresponding to the baseband signal.

44. The device according to claim 43, characterized in that The processing unit determines the unidirectional envelope modulation signal according to the first radio frequency electrical signal and the first electrical signal, specifically for: The first electrical signal is superimposed on the first radio frequency electrical signal to obtain the unidirectional envelope modulated signal.

45. The device according to claim 43 or 44, characterized in that The first electrical signal is time-synchronized with the first radio frequency electrical signal, and the amplitude of the first electrical signal is the same as the envelope amplitude of the first radio frequency electrical signal.

46. ​​The device according to claim 42, characterized in that The processing unit converts the first radio frequency electrical signal into a unidirectional envelope modulation signal, specifically for: Converting the first radio frequency electrical signal into a second radio frequency electrical signal, wherein the second radio frequency electrical signal is a positive half amplitude signal or a negative half amplitude signal of the first radio frequency electrical signal relative to a DC component; filtering the second radio frequency electrical signal to obtain a baseband signal and a basefrequency signal in the second radio frequency electrical signal; Adjusting the amplitudes of the baseband signal and the baseband signal on the frequency spectrum to obtain the unidirectional envelope modulation signal; The one-way envelope modulation signal is composed of the adjusted baseband signal and the adjusted baseband signal; the difference between the amplitude of the baseband component and the amplitude of the baseband component in the spectrum corresponding to the one-way envelope modulation signal is less than or equal to the second value.

47. The device according to any one of claims 42 to 46, characterized in that The processing unit is further configured to superimpose a first bias electrical signal on the unidirectional envelope modulated signal through an optical modulator; The processing unit is further configured to optically modulate the unidirectional envelope modulated signal superimposed with the first bias electrical signal through an optical modulator to obtain the first radio frequency optical signal.

48. The device according to claim 47, characterized in that The optical modulator is a directly modulated laser, and the first bias electrical signal is a first bias current signal; The current corresponding to the first bias current signal is greater than or equal to the threshold current of the direct-modulated laser, and the current corresponding to the first bias current signal is less than the first current.

49. The device according to claim 47, characterized in that The optical modulator is an electro-absorption modulator or a Mach-Zehnder modulator, the first bias electrical signal is a first bias voltage signal, and the voltage corresponding to the first bias voltage signal is greater than the first voltage.

50. The device according to any one of claims 42 to 49, characterized in that The processing unit is further configured to generate the first radio frequency electrical signal.

51. A communication device, characterized in that: The device comprises: A communication unit, configured to receive a first radio frequency optical signal; the first radio frequency optical signal is a unidirectional envelope radio frequency optical signal obtained by optically modulating a unidirectional envelope modulation signal, the lower envelope of which is flat and the lower envelope amplitude is less than or equal to a first value, and the carrier in the unidirectional envelope modulation signal is a sine wave; A processing unit, configured to convert the first radio frequency optical signal into a first radio frequency electrical signal; an upper envelope and a lower envelope of the first radio frequency electrical signal being symmetrical with respect to a DC component; Among them, the unidirectional envelope modulated signal is an RF electrical signal with a flat lower envelope, and the upper envelope of the unidirectional envelope modulated signal corresponds to the upper envelope of the first RF electrical signal; or, the unidirectional envelope modulated signal is an RF electrical signal with a flat upper envelope, and the lower envelope of the unidirectional envelope modulated signal corresponds to the lower envelope of the first RF electrical signal.

52. The device according to claim 51, characterized in that The first radio frequency electrical signal obtained by converting the first radio frequency optical signal is: a baseband signal in the unidirectional envelope modulated signal obtained by performing photoelectric conversion on the first radio frequency optical signal.

53. The device according to claim 52, characterized in that The processing unit converts the first radio frequency optical signal into the first radio frequency electrical signal, specifically for: Performing photoelectric conversion on the first radio frequency optical signal through a photoelectric detector to obtain the unidirectional envelope modulation signal; the passband of the photoelectric detector covers the spectrum of the baseband signal; The unidirectional envelope modulated signal is filtered through a bandpass filter to obtain the first radio frequency electrical signal; the passband of the bandpass filter only contains the frequency spectrum of the baseband signal.

54. The device according to claim 52, characterized in that The processing unit converts the first radio frequency optical signal into the first radio frequency electrical signal, specifically for: The first radio frequency optical signal is photoelectrically converted by a photoelectric detector to obtain the unidirectional envelope modulated signal, and the first radio frequency electrical signal is determined from the unidirectional envelope modulated signal; the passband of the photoelectric detector only includes the spectrum of the baseband signal.

55. A communication device, characterized in that: including memory and processor; The memory is used to store instructions or computer programs; The processor is used to execute the computer program or instructions stored in the memory so that the communication device executes the method described in any one of claims 1 to 9, or so that the communication device executes the method described in any one of claims 10 to 13.

56. A communication system, the communication system comprising a first communication device and a second communication device; The first communication device is used to perform the method according to any one of claims 1 to 9; The second communication device is used to execute the method according to any one of claims 10 to 13.

57. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 9 is implemented, or the method according to any one of claims 10 to 13 is implemented.

58. A computer program product, the computer program product comprising: Computer program code, when the computer program code is run, implements the method according to any one of claims 1 to 9, or implements the method according to any one of claims 10 to 13.

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