A quadruple-frequency communication and sensing integrated transmission system based on a single modulator

Abstract

The present invention belongs to the field of communication technologies, and specifically relates to a quadruple-frequency communication and sensing integrated transmission system based on a single modulator. The system of the present invention includes a transmitting end, a communication receiving end, and a sensing receiving end: The transmitting end includes a polarization division multiplexing Mach-Zehnder modulator, an external cavity laser, a waveform generator, a polarization controller, a polarization beam splitter, a fiber Bragg grating, an optical coupler, a photodetector, a transmitting antenna, etc.; The communication receiving end includes a receiving antenna, a mixer, and an oscilloscope; The sensing receiving end includes a receiving antenna, two mixers, and an oscilloscope; The system of the present invention uses a time-division multiplexed LFM-MQAM signal, which is equivalent to inserting block pilots, and can generate a broadband LFM signal to improve the ranging accuracy; The optical signal with the even-order sidebands dominant is output through the fiber Bragg grating to assist the photodetector in beating to generate a high-frequency millimeter-wave signal; The communication and sensing functions share devices, avoiding waste of hardware resources and improving the device integration level.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a quadruple-frequency communication and sensing integrated transmission system based on a single modulator. Background Art

[0002] With the continuous evolution of emerging services such as autonomous driving, drones, immersive extended reality, and industrial Internet, future data-driven intelligent applications will break the boundaries between the three major application scenarios of enhanced mobile broadband, ultra-reliable low-latency communication, and massive machine-type communication in the existing 5G mobile communication system. The 6G mobile communication system will be divided into more refined scenarios and needs to meet multi-dimensional extreme performance requirements at the same time. In past communication methods, communication and sensing functions existed independently. Among them, due to the lack of feedback information brought by the sensing function, the quality of communication could not be received in real time at the sending end, which had a certain negative impact on efficiency. If the communication part and the sensing part of the system can be combined to a certain extent to integrate the communication and sensing functions on one device, the communication quality of the system can be greatly improved, and the power consumption and hardware cost can be reduced. It has good development space in the application of future 6G technologies. Future intelligent applications not only require more extreme communication performance, but also need to perform environmental sensing in real time by means of technologies such as positioning, detection, and imaging. They also need to transmit sensing information to widely distributed computing nodes through ultra-wideband communication for intelligent processing, decision-making, and control of sensing information, and finally achieve ideal end-to-end performance. 6G is no longer just a simple pipeline for transmitting bits centered on humans, but also an intelligent and simple network that can sense all things, connect all things, and have intelligent endogenesis for the full interconnection of humans, machines, and things. Summary of the Invention

[0003] The purpose of the present invention is to provide a quadruple-frequency communication and sensing integrated transmission system based on a single modulator with a compact structure, simple operation, strong frequency doubling ability, and flexible frequency adjustment, so as to realize the sharing of hardware resources between communication devices and sensing devices and achieve high-rate communication and high-precision sensing.

[0004] The quadruple-frequency communication and sensing integrated transmission system based on a single modulator provided by the present invention includes a sending end, a communication receiving end, and a sensing receiving end: where:

[0005] (1) The sending end includes:

[0006] An external cavity laser (ECL), the light wave emitted by the laser is injected into a polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), and is divided into two paths by a 3-dB coupler built into the PDM-MZM, and respectively enters the two sub-modulators (MZM1 and MZM2) of the PDM-MZM. Among them, a part is modulated by the sub-modulator MZM1 working at the maximum bias point to generate even-order sidebands; another part is modulated by the sub-modulator MZM2 working at the minimum bias point to perform de-chirping on the echo signal received at the sensing end.

[0007] An arbitrary waveform generator (AWG), which is used to generate time-division multiplexed LFM and MQAM signals and drive the sub-modulator MZM1 of the optical modulator PDM-MZM.

[0008] A polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), the PDM-MZM consists of two sub-modulators (MZM1 and MZM2), a 90-degree polarization rotator (PR) and a polarization beam combiner (PBC); the function of MZM1 is to modulate the electrical signal generated by the AWG onto the optical carrier, and the function of MZM2 is to perform de-chirping on the down-converted echo signal; the PBC synthesizes the two paths of signals and outputs a polarization multiplexed signal.

[0009] A polarization controller (PC), which is used to control the polarization state of the output signal of the PDM-MZM.

[0010] A polarization beam splitter (PBS), which is used to divide the optical signal that has been modulated by the PDM-MZM and passed through the polarization controller into two paths.

[0011] An optical fiber Bragg grating (FBG), which suppresses the optical carrier of the signal output by MZM-1 and outputs ±2-order and ±4-order sideband optical signals.

[0012] Two optical couplers, denoted as the first optical coupler PM-OC1 and the second optical coupler PM-OC2. Among them, the first optical coupler PM-OC1 is used to divide the optical signal that has been modulated by the PDM-MZM and passed through the optical fiber Bragg grating to suppress the optical carrier into two paths, and the second optical coupler PM-OC2 is used to couple the lower path optical signal separated by the polarization beam splitter with the -4-order sideband optical signal selected by the wavelength selective switch (WSS).

[0013] Two photodetectors (PDs), which are used to complete photoelectric conversion by beat frequency. Among them, in the transmitting part, beat frequency generates time-division multiplexed LFM and MQAM signals in the millimeter wave band; for the sensing part, the electrical signal generated by PD2 by beat frequency is used for de-chirping.

[0014] A wavelength selective switch (WSS), which is used to select the -4-order sideband as the reference of the radar.

[0015] A transmitting antenna that transmits the millimeter-wave time-division multiplexed LFM and MQAM signals generated after beat frequency.

[0016] (2) The communication receiving end, including:

[0017] A communication receiving antenna for receiving millimeter-wave signals;

[0018] A mixer for down-converting the communication signals transmitted from the transmitting end received;

[0019] An oscilloscope for detecting the received communication signals and observing the time-domain waveforms and spectrograms of the signals.

[0020] (3) The sensing receiving end, including:

[0021] A sensing receiving antenna for obtaining the signals reflected from the receiving end;

[0022] Two mixers, one for converting the frequency of the received reflected signals to a lower frequency for down-conversion processing, and the other for down-converting the signals after the beat frequency of PD2 to facilitate oscilloscope sampling;

[0023] An oscilloscope for detecting the received sensing signals and observing the time-domain waveforms and spectrograms of the signals.

[0024] For the millimeter-wave communication and sensing integrated transmission system provided by the present invention, its sensing ranging principle is as follows:

[0025] Assume the sampling frequency is f s , the frequency modulation slope is k, τ represents the time delay of the echo signal, c is the speed of light, then the instantaneous frequency f N of the W-band LFM signal is:

[0026] f N = 4f s + 4kt; (1)

[0027] At the sensing demodulation end, the frequency of the de-chirped signal output by the second photodetector PD2 is 4kτ. Move the target to another position to obtain another de-chirped signal with a frequency of 4kτ'. Calculate the frequency difference Δf between the two positions, and the distance difference L between the two positions is:

[0028]

[0029] In the present invention, the time-division multiplexed LFM-MQAM signal is equivalent to inserting block pilots, which can generate broadband LFM signals, thereby improving the ranging accuracy;

[0030] In the present invention, an optical signal with dominant even-order sidebands is output through a fiber Bragg grating, and a high-frequency millimeter-wave signal is generated by beat frequency of an auxiliary photodetector, the first PD1.

[0031] In the present invention, the communication signal is a multi-carrier MQAM signal, and the sensing signal is a chirp signal.

[0032] In the present invention, the communication and sensing functions share devices, avoiding waste of hardware resources.

[0033] The present invention also relates to a communication and sensing integrated transmission method based on LFM-MQAM signals for the above transmission system. The specific steps are as follows:

[0034] At the transmitting end, the light wave emitted by an external cavity laser is injected into a modulator, PDM-MZM. It is divided into two paths by a 3-dB coupler built in the PDM-MZM and enters two sub-modulators (MZM1 and MZM2) of the PDM-MZM respectively. Among them, a part is modulated by the first sub-modulator MZM1 operating at the maximum bias point to generate even-order sidebands, and then is combined and output by a polarization beam combiner built in the optical modulator with the light wave modulated by the second sub-modulator MZM2 operating at the minimum bias point. The first optical coupler, PM-OC1, divides the optical carriers with dominant ±2nd and ±4th order sidebands output by the FBG into upper and lower paths. The upper-path optical carrier output by the first optical coupler PM-OC1 generates a high-frequency millimeter wave through beat frequency by the first photodetector PD1 for the communication function, while the lower-path optical carrier output by the first optical coupler PM-OC1 passes through a wavelength selection switch and is used as a part of the reference signal of the radar at the sensing receiving end;

[0035] The first optical coupler (PM-OC1) separates the upper sideband signal and the lower sideband signal of the signal output by the Bragg grating. The upper sideband signal is used for communication and sensing after subsequent processing, and the lower sideband signal is used as the reference optical signal at the ranging receiving end;

[0036] The upper sideband optical signal output by the first optical coupler PM-OC1 enters the first photodetector PD1 to complete beat frequency;

[0037] The first photodetector PD1 completes photoelectric conversion through beat frequency to obtain an LFM-MQAM signal in the millimeter-wave band. So far, the generation of communication and sensing signals has been completed;

[0038] The above signals are transmitted through an antenna and sent into the wireless channel;

[0039] At the communication receiving end, after wireless reception of the communication, the communication signal is coherently demodulated, and the demodulation method is the same as the modulation method;

[0040] At the sensing receiving end, the ranging signal reflected back is received through an antenna;

[0041] The sub - modulator MZM2 of the PDM - MZM modulator operating at the minimum bias point is driven by the down - converted signal obtained by mixing with the local oscillator signal, and is coupled with the - 4th order sideband optical signal output by the WSS using the second optical coupler PM - OC2;

[0042] The second photodetector PD2 receives the coupled signal output by the second optical coupler PM - OC2, beats to obtain a frequency peak, emits LFM signals to two targets respectively, and calculates the difference between the two frequency peaks to solve the distance between the two targets.

[0043] So far, the system has completed the functions of sensing ranging and communication.

[0044] Compared with the prior art, the present invention generates time - division multiplexed LFM and MQAM signals in the millimeter - wave band using optical heterodyne beating based on a single modulator and a single ECL, realizes the integration of hardware resources of sensing and communication devices, improves the hardware integration degree, and also meets the trend that the communication signal frequency bands with higher frequencies in the future gradually overlap with the radar signal spectrum bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the four - frequency communication and sensing integrated transmission system architecture based on a single modulator of the present invention.

[0046] Reference numerals in the figure: 1 is the laser generator ECL, 2 is the arbitrary waveform generator AWG, 3 is the sub - modulator MZM1 of the optical modulator PDM - MZM, 4 is the sub - modulator MZM2 of the optical modulator PDM - MZM, 5 is the 90 - degree polarization rotator PR of the optical modulator PDM - MZM, 6 is the polarization beam combiner PBC of the optical modulator PDM - MZM, 7 is the polarization controller PC, 8 is the polarization beam splitter PBS, 9 is the fiber Bragg grating FBG, 10 is the first optical coupler PM - OC1, 11 is the first photodetector PD1, 12 is the transmitting antenna HA1, 13 is the communication receiving antenna HA2, 14 is the local oscillator ELO1, 15 is the first mixer, 16 is the oscilloscope OSC, 17 is the wavelength selection switch WSS, 18 is the second mixer, 19 is the local oscillator ELO2, 20 is the sensing receiving antenna HA3, 21 is the target to be measured, 22 is the second optical coupler PM - OC2, 23 is the second photodetector PD2, 24 is the third mixer, 25 is the oscilloscope OSC. DETAILED DESCRIPTION OF THE INVENTION

[0047] The following further describes the present invention with reference to the accompanying drawings.

[0048] The four - frequency communication and sensing integrated transmission system based on a single modulator provided by the present invention has an architecture as shown in Figure 1 where:

[0049] At the transmitting end, based on time-division multiplexing LFM, the MQAM signal is generated by MATLAB programming. Since the MQAM signal for the communication function is frequency-doubled, pre-coding processing is performed on the MQAM signal at this stage, and then it is uploaded to an arbitrary waveform generator (2). The intermediate frequency signal generated by the arbitrary waveform generator (2) drives the first sub-modulator MZM1 (3) of the optical modulator to modulate the optical carrier output by the laser (1) to generate even-order sidebands. The polarization beam combiner PBC (6) of the polarization division multiplexing MZM of the optical modulator combines the two signals of the two sub-modulators to output a polarization multiplexed signal. The polarization multiplexed signal output by the polarization beam combiner PBC (6) is divided into two paths by a polarization beam splitter (8) after the polarization state is controlled by a polarization controller (7). One path passes through a fiber Bragg grating (9) to suppress the optical carrier and is then divided into two paths by the first polarization-maintaining optical coupler PM-OC1 (10). After the upper path is beat-frequency detected by the first photodetector PD1 (11), it is transmitted through a suitable transmitting antenna (12).

[0050] At the communication receiving end, the millimeter-wave signal in the W band used for the communication function is received by the communication receiving antenna (12). The local oscillator ELO1 (14) generates a fixed-frequency signal to perform down-conversion processing on the communication signal using the first mixer (15). The demodulation method corresponds to the modulation method. A series of digital signal processing is used to recover the MQAM signal, and the signal is received through an oscilloscope (16).

[0051] At the sensing receiving end, the echo signal from the measured target (21) is received through the sensing receiving antenna (20). The down-conversion of the signal is completed at the second mixer (18) and the local oscillator ELO2 (19). At this time, the down-converted signal is sent back to the polarization division multiplexing MZM of the optical modulator to drive the second sub-modulator MZM2 (4) for de-chirping. After passing through a 90-degree polarization rotator PR (5), it is combined with the signal output by the first sub-modulator MZM1 (3) by the polarization beam combiner PBC (6) to output a polarization multiplexed signal. The lower-path optical signal separated by the first polarization-maintaining optical coupler PM-OC1 (10) at the transmitting end selects the -4th order sideband optical signal through a wavelength selection switch (17) and is coupled with the lower-path signal separated by the polarization beam splitter (8) at the second polarization-maintaining optical coupler PM-OC2 (22). After photoelectric conversion is completed by beat-frequency detection by the second photodetector PD2 (23), it is down-converted by the third mixer (24) and the received signal is detected through an OSC oscilloscope (25).

[0052] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A quadruple-frequency communication and sensing integrated transmission system based on a single modulator, characterized in that Including a transmitting end, a communication receiving end, and a sensing receiving end: Among them: The transmitting end includes: A polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), which is composed of a first sub-modulator (MZM1), a second sub-modulator (MZM2), a 90-degree polarization rotator (PR), and a polarization beam combiner (PBC); the function of the first sub-modulator (MZM1) is to modulate the electrical signal generated by the arbitrary waveform generator (AWG) onto the optical carrier, and the function of the second sub-modulator (MZM2) is to de-chirp the down-converted echo signal; the polarization beam combiner (PBC) synthesizes the two signals into a polarization multiplexed signal for output; An external cavity laser (ECL), the light wave emitted by the external cavity laser is injected into the polarization division multiplexing Mach-Zehnder modulator (PDM-MZM), and is divided into two paths by a 3-dB coupler built in the modulator (PDM-MZM), and respectively enter the first sub-modulator (MZM1) and the second sub-modulator (MZM2) of the modulator (PDM-MZM). Among them, a part is modulated by the sub-modulator (MZM1) operating at the maximum bias point to generate even-order sidebands; the other part is modulated by the second sub-modulator (MZM2) operating at the minimum bias point, which is used to de-chirp the echo signal received by the sensing end; An arbitrary waveform generator (AWG), which is used to generate time-division multiplexed LFM and MQAM signals and drive the first optical sub-modulator (MZM1); A polarization controller (PC), which is used to control the polarization state of the signal output by the modulator (PDM-MZM); A polarization beam splitter (PBS), which is used to divide the optical signal modulated by the modulator (PDM-MZM) and passing through the polarization controller into two paths; An optical fiber Bragg grating (FBG), which suppresses the optical carrier of the signal output by the first sub-modulator (MZM-1) and outputs ±2-order and ±4-order sideband optical signals; Two optical couplers, namely the first optical coupler (PM-OC1) and the second optical coupler (PM-OC2). Among them, the first optical coupler (PM-OC1) is used to divide the optical signal modulated by the modulator (PDM-MZM) and having the optical carrier suppressed by the optical fiber Bragg grating (FBG) into two paths; the second optical coupler (PM-OC2) is used to couple the lower-path optical signal separated by the polarization beam splitter (PBS) with the -4-order sideband optical signal selected by the wavelength selective switch (WSS); Two photodetectors (PD), namely the first photodetector (PD1) and the second photodetector (PD2), which are used to complete photoelectric conversion by beat frequency; among them, in the transmitting part, the first photodetector (PD1) generates time-division multiplexed LFM and MQAM signals in the millimeter wave band by beat frequency; for the sensing part, the electrical signal generated by the second photodetector (PD2) by beat frequency is used for de-chirping; A wavelength selective switch (WSS), which is used to select the -4-order sideband as the reference for the radar; A transmitting antenna, which transmits the millimeter wave time-division multiplexed LFM and MQAM signals generated after beat frequency; The communication receiving end comprises: a communication receiving antenna for receiving millimeter wave signals; A mixer for down-converting the communication signal received from the transmitter; An oscilloscope, used to detect the received communication signal and observe the signal time domain waveform and spectrum; The sensing receiving end comprises: A sensing receiving antenna for acquiring the signal reflected from the receiving end; Two mixers, one for converting the received reflected signal frequency to a lower frequency for down-conversion processing, and the other for down-converting the signal after the beat frequency of the second photodetector (PD2) for oscilloscope sampling; An oscilloscope is used to detect the received perception signal and observe the signal time domain waveform and spectrum diagram.

2. The quadruple-frequency communication and sensing integrated transmission system according to claim 1, wherein The use of time-division multiplexed LFM-MQAM signals is equivalent to inserting block pilots, which can generate broadband LFM signals and thus improve the ranging accuracy.

3. The quadruple-frequency communication and sensing integrated transmission system according to claim 1, wherein The fiber Bragg grating outputs an optical signal dominated by even-order sidebands, which assists the photodetector (PD) beat frequency to generate a high-frequency millimeter-wave signal.

4. The quadruple-frequency communication and sensing integrated transmission system according to claim 1, wherein The communication signal is a multi-carrier MQAM signal, and the perception signal is a linear frequency modulation signal.

5. The quadruple-frequency communication and sensing integrated transmission system according to claim 1, wherein Communication and perception functions share equipment to avoid wasting hardware resources.

6. The quadruple-frequency communication and sensing integrated transmission system according to claim 1, wherein The workflow is: At the transmitting end, the light wave emitted by the external cavity laser is injected into the modulator (PDM-MZM), and is divided into two paths by the built-in 3-dB coupler of the modulator (PDM-MZM), and enters two sub-modulators (MZM1 and MZM2) respectively; one part is modulated by the first sub-modulator (MZM1) working at the maximum bias point to generate even-order sidebands, and the other part is modulated by the second sub-modulator (MZM2) working at the minimum bias point; the two modulated parts of the light wave are synthesized and output by the built-in polarization beam combiner (PBC) of the optical modulator, and the first optical coupler (PM-OC1) divides the optical carrier dominated by the ±2nd and ±4th order sidebands output by the fiber Bragg grating (FBG) into upper and lower paths, and the upper optical carrier output by the first optical coupler (PM-OC1) is beat by the first photodetector (PD1) to generate high-frequency millimeter waves for communication functions, while the lower optical carrier output by the first optical coupler (PM-OC1) is used as part of the reference signal for sensing the radar at the receiving end through the wavelength selective switch; The first optical coupler (PM-OC1) separates the upper sideband signal and the lower sideband signal of the Bragg grating output signal. The upper sideband signal is used for communication and perception after subsequent processing, and the lower sideband signal is used as a reference optical signal for the ranging receiving end; The upper sideband optical signal output by the first optical coupler (PM-OC1) enters the first photodetector (PD1) to complete the beat frequency; The first photodetector (PD1) completes the photoelectric conversion by beating the frequency to obtain the LFM-MQAM signal in the millimeter wave band, thus completing the generation of the communication sensing signal; The above signal is transmitted through the transmitting antenna and sent into the wireless channel; At the communication receiving end, after wireless reception by the communication receiving end, the communication signal is coherently demodulated, and the demodulation method is consistent with the modulation method; At the sensing receiving end, the reflected ranging signal is received by the sensing receiving antenna; The down-converted signal obtained by mixing with the local oscillator signal is used to drive the second sub-modulator (MZM2) operating at the minimum bias point, and is coupled with the -4th order sideband optical signal output by the second optical coupler (PM-OC2) and the wavelength selective switch (WSS); The second photodetector (PD2) receives the coupled signal output by the second optical coupler (PM-OC2), beats to obtain a frequency peak, emits LFM signals to two targets respectively, and calculates the difference between the two frequency peaks to solve the distance between the two targets; So far, the functions of sensing ranging and communication have been completed.

7. The quadruple-frequency communication and sensing integrated transmission system according to claim 6, wherein The principle of the sensing ranging is as follows: Assume the sampling frequency is f s , the frequency modulation slope is k, τ represents the time delay of the echo signal, c is the speed of light, then the instantaneous frequency f N of the W-band LFM signal is as follows: f N = 4f s + 4kt; (1) At the sensing demodulation end, the frequency of the de-chirped signal output by the second photodetector (PD2) is 4kτ. Move the target to another position to obtain another de-chirped signal with a frequency of 4kτ′. Calculate the frequency difference Δf between the two positions, and the distance difference L between the two positions is:

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