Radio frequency pilot frequency assisted high linewidth tolerance photon-assisted communication system

Abstract

The invention relates to the technical field of optical fiber communication and wireless communication systems, and discloses a radio-frequency pilot-assisted high-linewidth tolerance photon-assisted communication system, which comprises a signal transmitting end and a signal receiving end, wherein the signal transmitting end comprises a transmitting end digital signal processing unit which is mainly responsible for generating a single-carrier or multi-carrier signal and inserting a pilot signal; according to the high-linewidth-tolerance photon-assisted communication system assisted by the radio frequency pilot frequency provided by the invention, a photon-assisted millimeter wave / terahertz communication system with high laser linewidth tolerance is realized in an assisted manner based on an advanced digital signal algorithm and the radio frequency pilot frequency; the problems that in a traditional photon-assisted millimeter wave / terahertz communication scheme, a narrow linewidth laser is needed for heterodyne, and a high-complexity digital signal algorithm is needed for solving phase noise are effectively solved, and high-quality generation and transmission of millimeter wave / terahertz signals are successfully achieved under the MHz linewidth distributed feedback type laser.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication and wireless communication systems, and in particular to a high line width tolerance photon-assisted communication system assisted by a radio frequency pilot. Background Art

[0002] With the commercialization of 5G communication networks, emerging applications are driving the exponential growth of network data traffic. At present, the frequency bands used by traditional mobile communications are saturated and cannot meet the future high-throughput communication needs. In order to solve the explosive growth in traffic demand, researchers have turned their attention to the millimeter wave (MMW) and terahertz (THz) frequency bands, which are located between 30GHz and 1THz, have rich spectrum resources and unlicensed features, and can support hundreds of Gbps of communication rates. Therefore, researchers from various countries have started research on high-frequency millimeter wave / terahertz communications, among which the millimeter wave / terahertz communication scheme based on photon-assisted technology has attracted widespread attention from researchers because it can overcome the bandwidth bottleneck of electronic devices and has flexible frequency tunability.

[0003] However, in order to ensure the quality of the generated millimeter wave / terahertz signal, the current photon-assisted scheme usually requires a narrow linewidth laser to perform heterodyne beat frequency to reduce the impact of phase noise, but this increases the system cost to a certain extent. In addition, unlike the all-solid-state electronic link scheme that uses a phase-locked loop circuit to achieve phase noise compensation, the photon-assisted scheme receiver usually requires complex digital signal processing algorithms to achieve phase noise compensation, which also increases the complexity of system processing to a certain extent.

[0004] If RF pilot can be used for assistance, and low-complexity digital signal processing technology can be used to solve the phase noise problem in the optical millimeter wave communication system, the tolerance of the photon-assisted scheme to the laser line width can be improved, which will be of great significance for the engineering application of photon-assisted millimeter wave / terahertz communication technology. Summary of the invention

[0005] The purpose of the present invention is to provide a high linewidth tolerance photon-assisted communication system assisted by a radio frequency pilot. By using radio frequency assistance and low-complexity digital signal processing, the phase noise problem in the optical millimeter wave / terahertz scheme is effectively solved, the tolerance of the photon-assisted millimeter wave / terahertz scheme to the laser linewidth is improved, and a photon-assisted millimeter wave / terahertz communication system with high laser linewidth tolerance is realized. Based on the photon-assisted millimeter wave / terahertz scheme assisted by a radio frequency pilot, when the two light sources used for heterodyning are distributed feedback lasers (DFBs) with a linewidth of MHz level, the generation and transmission of broadband millimeter wave / terahertz signals are realized. Compared with the traditional photon-assisted millimeter wave / terahertz scheme, the use of radio frequency pilot in this scheme effectively improves the tolerance of the optical millimeter wave / terahertz scheme to the laser linewidth, and greatly reduces the complexity of the digital signal processing algorithm used for phase noise compensation at the receiving end and the system cost.

[0006] The radio frequency pilot-assisted high linewidth tolerance photon-assisted communication system provided by the present invention includes the following steps, in the order of signal transmission direction:

[0007] 1. Digital signal processing at the transmitter

[0008] A transmitting end digital signal processing unit includes signal generation and RF pilot insertion. In particular, for a single carrier transmission system, the RF pilot signal is directly inserted in the digital domain after baseband shaping, specifically taking equation (1) as an example.

[0009] s(t)=[I(t)+jQ(t)]+exp(j2πf c t) (1)

[0010] Where I(t) and Q(t) are the real and imaginary components of the complex baseband signal, f c is the frequency at which the pilot signal is inserted, usually f c It needs to be larger than the maximum signal bandwidth by about 1 GHz to ensure sufficient protection interval.

[0011] For a multi-carrier transmission system, the pilot signal is inserted by assigning data to the DC subcarrier (the first subcarrier), specifically taking equation (2) as an example.

[0012]

[0013] Among them, s krepresents the data symbol assigned to the Kth subchannel, N represents the number of subcarriers, T represents the symbol period, rect() represents the rectangular function, s0=A represents the data of the first subcarrier as a constant, and the frequency domain represents the inserted pilot component. It should be noted that in order to avoid the influence of phase noise, this scheme also requires a guard interval, that is, the data of the adjacent subcarriers of the first subcarrier need to be set to zero.

[0014] At this point, the digital signal processing part of the single-carrier or multi-carrier transmitter is completed.

[0015] 2. Signal sending end:

[0016] A C-band, wavelength-tunable laser, which may be a distributed feedback laser (DFB) or an external cavity laser (ECL), is used to generate a C-band optical carrier and is vector modulated by an in-phase / quadrature (I / Q) optical modulator;

[0017] a digital-to-analog conversion device, such as an arbitrary waveform generator (AWG), for converting the real and imaginary parts of the digital signal generated by the digital signal processing unit at the transmitting end into two baseband analog electrical signals;

[0018] Two electrical amplifiers (EA), namely electrical amplifier 1 and electrical amplifier 2, are used to amplify two baseband analog electrical signals generated by the digital-to-analog conversion device respectively;

[0019] an in-phase / quadrature (I / Q) optical modulator for modulating two analog baseband electrical signals onto an optical carrier to generate signal light;

[0020] A polarization-maintaining erbium-doped fiber amplifier (PM-EDFA), used to amplify the signal light output by the optical modulator and compensate for the insertion loss of the modulator;

[0021] a C-band, wavelength-tunable laser 2, which is a distributed feedback laser (DFB) or an external cavity laser (ECL), for generating a local oscillator optical signal for heterodyning;

[0022] A polarization-maintaining optical coupler (PM-OC) is used to couple the amplified signal light with the local oscillator light generated by another laser (DFB or ECL). By adjusting the wavelength difference between the local oscillator light and the signal light, the generation of millimeter-wave / terahertz signals of different frequency bands can be achieved;

[0023] a photoelectric converter (PD), such as a photodiode, for converting an optical millimeter wave / terahertz signal output by a polarization-maintaining optical coupler (PM-OC) into an electrical millimeter wave signal / terahertz signal, which is then amplified with or without passing through an electrical amplifier;

[0024] a transmitting antenna device for transmitting the generated electrical millimeter wave / terahertz signal into free space for transmission;

[0025] So far, the transmission of single-carrier or multi-carrier electrical millimeter wave / terahertz signals has been completed;

[0026] 3. Signal receiving end

[0027] a receiving antenna device for receiving an electrical millimeter wave / terahertz signal and then amplifying the millimeter wave / terahertz signal with or without an electrical amplifier;

[0028] A radio frequency signal generator, used to generate a local oscillator electrical signal required for down-conversion;

[0029] a mixer for analog down-converting the received electrical millimeter wave / terahertz signal from the millimeter wave / terahertz frequency band to the radio frequency band;

[0030] an electrical amplifier 3, for amplifying the intermediate frequency signal after down-conversion;

[0031] An analog-to-digital conversion device, such as an oscilloscope (OSC), is used to capture the amplified intermediate frequency signal and observe the time domain and frequency domain diagrams of the signal.

[0032] 4. Digital signal processing at the receiving end

[0033] The digital signal processing unit at the receiving end is used to perform frequency deviation and phase noise compensation for the signal and channel equalization, wherein the frequency deviation and phase noise compensation are based on the proposed RF pilot auxiliary scheme. For a single-carrier signal: first, the frequency deviation is corrected according to the pilot position, and then the pilot is down-converted to the zero-frequency (DC) component; at this time, the signal is low-pass filtered, and the extracted DC component phase information is the phase noise of the system; then the signal before filtering is multiplied by the conjugate component of the phase noise to complete the phase noise compensation; finally, digital signal processing such as signal down-conversion and channel equalization is performed; for multi-carrier signals: the signal is down-converted and the frequency deviation is corrected directly according to the pilot position, and then low-pass filtering is performed to extract the phase noise and the time domain signal before filtering is multiplied by the conjugate component of the phase noise to complete the phase noise compensation, and finally the multi-carrier signal is demodulated.

[0034] Preferably, the RF pilot insertion method in the digital signal processing unit at the transmitting end is: a single carrier directly generates a digital subcarrier in the digital domain; a multi-carrier scheme directly assigns the data of the first subcarrier to a constant, and the frequency domain is represented by a digital subcarrier located at the center of the signal.

[0035] Preferably, the position where the RF pilot is inserted in the digital signal processing unit at the transmitting end is: both single-carrier and multi-carrier schemes need to reserve a protection interval, and the single-carrier pilot position needs to be about 1 GHz away from the maximum component of the signal bandwidth. The specific interval size is related to the laser line width. The larger the line width, the larger the protection interval; conversely, the smaller the laser line width, the smaller the protection interval; the multi-carrier protection interval is achieved by setting the subcarriers near the first subcarrier to zero. The larger the required protection interval, the more subcarriers are set to zero.

[0036] Preferably, the frequency offset compensation method is as follows: Different from the conventional digital signal processing scheme, the frequency offset compensation of single carrier and multi-carrier in the pilot-assisted scheme is realized by locating the position of the pilot component to correct the frequency offset.

[0037] Preferably, the phase noise compensation method is: different from the conventional digital signal processing scheme, the compensation of single-carrier and multi-carrier phase noise in the pilot-assisted scheme is performed by extracting the phase information of the pilot component; specifically, the pilot component is extracted by low-pass filtering in both the single-carrier and multi-carrier schemes, and then the phase of the pilot component is inverted, and finally multiplied with the time domain signal before the filter to complete the phase noise compensation.

[0038] Preferably, the laser type in the photon-assisted scheme is: different from the narrow-linewidth laser, the teeth of the optical frequency comb or the optical injection-locked optical carrier used in conventional optically generated millimeter-wave / terahertz communication schemes, the pilot-assisted scheme uses a large-linewidth, low-cost distributed feedback laser as a heterodyne optical carrier.

[0039] Preferably, the pilot-assisted frequency offset and phase noise compensation scheme effectively improves the ability of the optically generated millimeter wave / terahertz system to compensate for frequency offset and phase noise, and improves the transmission performance of the system.

[0040] Preferably, when two laser beams with a line width of MHz level are used as heterodyne optical carriers, the transmission of signals with a bandwidth of 20 GHz and 16 / 32 / 64 orthogonal amplitude phase modulation is achieved.

[0041] Preferably, when two distributed feedback lasers are used as heterodyne optical carriers, the generation and transmission of optical millimeter wave / terahertz signals are realized, which greatly reduces the demand for narrow linewidth lasers in traditional optical millimeter wave / terahertz communication system solutions.

[0042] The present invention also proposes a high linewidth tolerance photon-assisted communication scheme assisted by a radio frequency pilot, comprising the following steps:

[0043] In the digital signal processing unit at the transmitting end, multi-carrier or single-carrier signal generation and pilot insertion are respectively performed, and then the generated digital signal is converted into digital-to-analog using a digital-to-analog conversion device (such as an arbitrary waveform generator) to realize the generation of two baseband electrical signals of in-phase and quadrature (I / Q), and the two baseband electrical signals generated are respectively amplified by electrical amplifier 1 and electrical amplifier 2 and used to drive the in-phase / quadrature (I / Q) optical modulator; laser 1 is used to generate a C-band optical carrier and then use the optical modulator for vector modulation; a polarization-maintaining erbium-doped fiber amplifier (PM-EDFA) is used to amplify the optical baseband signal output by the optical modulator; another laser 2 is used to generate an optical local oscillator signal, and then the amplified optical signal is coupled with the polarization-maintaining erbium-doped optical amplifier through a polarization-maintaining optical coupler (PM-OC) to generate an optical millimeter wave / terahertz signal, and the coupled optical millimeter wave / terahertz signal is converted into an electrical millimeter wave / terahertz signal through an optoelectronic converter, and then radiated to free space through the transmitting end antenna device;

[0044] At the receiving end, the transmitted electrical millimeter wave / terahertz signal is received by the receiving end antenna device, and the RF signal generator is used to provide the electrical local oscillator signal required by the mixer. The received electrical millimeter wave / terahertz signal then enters the mixer together with the local oscillator electrical signal for analog down-conversion. The intermediate frequency signal after down-conversion by the mixer is amplified by an electrical amplifier three, and then received by an analog-to-digital conversion device (such as an oscilloscope) and digital signal processing at the receiving end is performed, which mainly includes frequency deviation and phase noise compensation and channel equalization based on pilot assistance.

[0045] Generate broadband, high-frequency electrical millimeter-wave / terahertz signals using optical heterodyne beat frequency, and change the frequency of the generated millimeter-wave / terahertz signals by tuning the wavelength difference between the two laser beams;

[0046] At the receiving end, an antenna device is used to receive the electrical millimeter wave / terahertz signal, and a mixer is used for superheterodyne reception to realize down-conversion of the electrical millimeter wave / terahertz signal. Finally, an analog-to-digital conversion device such as an oscilloscope is used for data acquisition. The digital signal processing unit at the receiving end completes the compensation of frequency deviation and phase noise by locating the position of the pilot component, low-pass filtering and phase inversion.

[0047] So far, the system has completed the generation and transmission of high-linewidth-tolerance photon-assisted terahertz / millimeter-wave signals based on RF pilot assistance.

[0048] Compared with the related art, the high linewidth tolerance photon-assisted communication system assisted by the radio frequency pilot provided by the present invention has the following beneficial effects:

[0049] Compared with the prior art, the high linewidth tolerance photon-assisted communication system assisted by the RF pilot provided by the present invention can effectively improve the tolerance of the optically generated millimeter wave / terahertz communication scheme to the laser linewidth, while reducing the complexity of the phase noise and frequency offset compensation algorithm;

[0050] The RF pilot scheme improves the system's tolerance to frequency deviation and phase noise, and the expensive narrow-linewidth lasers in the traditional photon-assisted scheme can be replaced with cheaper wide-linewidth lasers, which can greatly save the system cost of the photon-assisted scheme.

[0051] Based on advanced digital signal processing technology and RF pilot-assisted photon-assisted millimeter-wave / terahertz solutions, a photon-assisted millimeter-wave / terahertz communication system with wide laser linewidth tolerance can be realized, providing a feasible solution for future high-frequency millimeter-wave terahertz communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of a high linewidth tolerance photon-assisted communication system assisted by a radio frequency pilot provided by the present invention, in which the solid line portion is an optical signal and the dotted line portion is an electrical signal;

[0053] Figure 2 is a schematic diagram of the power spectrum of a multi-carrier transmission signal, which includes a pilot at a zero-frequency component;

[0054] Figure 3 It is a schematic diagram of the power spectrum of a single-carrier transmission signal, which includes the inserted pilot component;

[0055] Figure 4 It is a schematic diagram of the power spectrum of the pilot component extracted after the multi-carrier received signal is low-pass filtered;

[0056] Figure 5 It is a schematic diagram of phase noise components extracted from a multi-carrier received signal using pilot components;

[0057] Figure 6 It is a schematic diagram of the power spectrum of the pilot component extracted after low-pass filtering of the single-carrier received signal;

[0058] Figure 7 It is a schematic diagram of phase noise components proposed by using pilot components for a single carrier received signal;

[0059] Figure 8 It is a performance curve of 20GHz bandwidth multi-carrier terahertz transmission based on RF pilot scheme assisted by DFB laser, which specifically shows the relationship between received optical power and bit error rate;

[0060] Fig. 9It is the performance curve of 20 GHz baud single-carrier terahertz transmission based on the RF pilot scheme under DFB laser, which specifically shows the relationship between the received optical power and the bit error rate.

[0061] Attached Figure 1 Chinese markings: 1. Transmitter digital signal processing unit; 2. Digital-to-analog conversion device; 3. Electric amplifier one; 4. Electric amplifier two; 5. Laser one; 6. Optical modulator; 7. Polarization-maintaining erbium-doped fiber amplifier; 8. Laser two; 9. Polarization-maintaining optical coupler; 10. Photoelectric converter; 11. Transmitter antenna device; 12. Receiver antenna device; 13. Mixer; 14. RF signal generator; 15. Electric amplifier three; 16. Analog-to-digital conversion device. DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0063] See also Figure 1-9 ,in, Figure 1 Schematic diagram of a high linewidth tolerance photon-assisted communication system assisted by a radio frequency pilot provided by the present invention, in which the solid line portion is an optical signal and the dotted line portion is an electrical signal; Figure 2 is a schematic diagram of the power spectrum of a multi-carrier transmission signal, which includes a pilot at a zero-frequency component; Figure 3 It is a schematic diagram of the power spectrum of a single-carrier transmission signal, which includes the inserted pilot component; Figure 4 It is a schematic diagram of the power spectrum of the pilot component extracted after the multi-carrier received signal is low-pass filtered; Figure 5 It is a schematic diagram of phase noise components extracted from a multi-carrier received signal using pilot components; Figure 6 It is a schematic diagram of the power spectrum of the pilot component extracted after low-pass filtering of the single-carrier received signal; Figure 7 It is a schematic diagram of phase noise components proposed by using pilot components for a single carrier received signal; Figure 8 It is a performance curve of 20GHz bandwidth multi-carrier terahertz transmission based on RF pilot scheme assisted by DFB laser, which specifically shows the relationship between received optical power and bit error rate; Fig. 9 It is the performance curve of 20 GHz baud single-carrier terahertz transmission based on the RF pilot scheme under DFB laser, which specifically shows the relationship between the received optical power and the bit error rate.

[0064] The embodiment of the present invention proposes a high line width tolerance photon-assisted communication system assisted by a radio frequency pilot, such as Figure 1 As shown, the order of description is based on the signal transmission direction, including:

[0065] (1) Digital signal processing at the transmitting end

[0066] A transmitting end digital signal processing unit 1 includes signal generation and RF pilot insertion. In particular, for a single carrier transmission system, the RF pilot signal is directly inserted in the digital domain after baseband shaping, specifically taking formula (1) as an example.

[0067] s(t)=[I(t)+jQ(t)]+exp(j2πf c t) (1)

[0068] Where I(t) and Q(t) are the real and imaginary components of the complex baseband signal, f c is the frequency at which the pilot signal is inserted, usually f c It needs to be larger than the maximum signal bandwidth by about 1 GHz to ensure sufficient protection interval.

[0069] For a multi-carrier transmission system, the pilot signal is inserted by assigning data to the DC subcarrier (the first subcarrier), specifically taking equation (2) as an example.

[0070]

[0071] Among them, s k represents the data symbol assigned to the Kth subchannel, N represents the number of subcarriers, T represents the symbol period, rect() represents the rectangular function, s0=A represents the data of the first subcarrier as a constant, and the frequency domain represents the inserted pilot component. It should be noted that in order to avoid the influence of phase noise, this scheme also requires a guard interval, that is, the data of the adjacent subcarriers of the first subcarrier need to be set to zero.

[0072] At this point, the digital signal processing part of the single-carrier or multi-carrier transmitter is completed.

[0073] (2) Signal sending end:

[0074] A C-band, wavelength-tunable laser 5, which may be a distributed feedback laser (DFB) or an external cavity laser (ECL) for generating a C-band optical carrier and performing vector modulation via an in-phase / quadrature (I / Q) optical modulator 6;

[0075] A digital-to-analog conversion device 2, such as an arbitrary waveform generator (AWG), is used to convert the real part and the imaginary part of the digital signal generated by the digital signal processing unit 1 at the transmitting end into two baseband analog electrical signals;

[0076] Two electrical amplifiers (EA), namely electrical amplifier 1 3 and electrical amplifier 2 4, are used to amplify two baseband analog electrical signals generated by the digital-to-analog conversion device 2;

[0077] an in-phase / quadrature (I / Q) optical modulator 6, used to modulate two analog baseband electrical signals onto an optical carrier to generate signal light;

[0078] a polarization-maintaining erbium-doped fiber amplifier (PM-EDFA) 7, used to amplify the signal light output by the optical modulator 6 and compensate for the insertion loss of the modulator;

[0079] A C-band, wavelength-tunable laser 28, which is a distributed feedback laser (DFB) or an external cavity laser (ECL), for generating a local oscillator optical signal for heterodyning;

[0080] A polarization-maintaining optical coupler (PM-OC) 9 is used to couple the amplified signal light with the local oscillator light generated by another laser (DFB or ECL) 8. By adjusting the wavelength difference between the local oscillator light and the signal light, the generation of millimeter-wave / terahertz signals of different frequency bands can be achieved;

[0081] a photoelectric converter (PD), such as a photodiode, for converting the optical millimeter wave / terahertz signal output by the polarization-maintaining optical coupler (PM-OC) 9 into an electrical millimeter wave signal / terahertz signal, which is then amplified with or without an electrical amplifier;

[0082] a transmitting antenna device 11, for transmitting the generated electrical millimeter wave / terahertz signal into free space for transmission;

[0083] So far, the transmission of single-carrier or multi-carrier electrical millimeter wave / terahertz signals has been completed;

[0084] (3) Signal receiving end

[0085] a receiving antenna device 12 for receiving electrical millimeter wave / terahertz signals and then amplifying the millimeter wave / terahertz signals with or without an electrical amplifier;

[0086] A radio frequency signal generator 14, used to generate a local oscillator electrical signal required for down-conversion;

[0087] A mixer 13, used for analog down-converting the received electrical millimeter wave / terahertz signal from the millimeter wave / terahertz frequency band to the radio frequency band;

[0088] An electrical amplifier 3 15, for amplifying the intermediate frequency signal after down-conversion;

[0089] An analog-to-digital conversion device 16, such as an oscilloscope (OSC), is used to capture the amplified intermediate frequency signal and observe the time domain and frequency domain diagrams of the signal.

[0090] (4) Digital signal processing at the receiving end

[0091] The digital signal processing unit at the receiving end is used to perform frequency deviation and phase noise compensation for the signal and channel equalization, wherein the frequency deviation and phase noise compensation are based on the proposed RF pilot auxiliary scheme. For a single-carrier signal: first, the frequency deviation is corrected according to the pilot position, and then the pilot is down-converted to the zero-frequency (DC) component; at this time, the signal is low-pass filtered, and the extracted DC component phase information is the phase noise of the system; then the signal before filtering is multiplied by the conjugate component of the phase noise to complete the phase noise compensation; finally, digital signal processing such as signal down-conversion and channel equalization is performed; for multi-carrier signals: the signal is down-converted and the frequency deviation is corrected directly according to the pilot position, and then low-pass filtering is performed to extract the phase noise and the time domain signal before filtering is multiplied by the conjugate component of the phase noise to complete the phase noise compensation, and finally the multi-carrier signal is demodulated.

[0092] The embodiment of the present invention further proposes a high linewidth tolerance photon-assisted communication solution assisted by a radio frequency pilot, comprising the following steps:

[0093] In the digital signal processing unit 1 at the transmitting end, multi-carrier or single-carrier signal generation and pilot insertion are respectively performed, and then the generated digital signal is converted into digital-to-analog by using a digital-to-analog conversion device 2 (such as an arbitrary waveform generator) to realize the generation of in-phase and quadrature (I / Q) baseband electrical signals. The generated two baseband electrical signals are respectively amplified by an electrical amplifier 1 3 and an electrical amplifier 2 4 and used to drive an in-phase / quadrature (I / Q) optical modulator 6; a laser 1 5 is used to generate a C-band optical carrier and then perform vector modulation using the optical modulator 6; a polarization-maintaining erbium-doped fiber amplifier 7 is used to amplify the optical baseband signal output by the optical modulator 6; another laser 2 8 is used to generate an optical local oscillator signal, and then the amplified optical signal is coupled with the polarization-maintaining erbium-doped optical amplifier 7 through a polarization-maintaining optical coupler 9 to generate an optical millimeter wave / terahertz signal, and the coupled optical millimeter wave / terahertz signal is converted into an electrical millimeter wave / terahertz signal through an optoelectronic converter 10, and then radiated to free space through a transmitting end antenna device 11;

[0094] At the receiving end, the transmitted electrical millimeter wave / terahertz signal is received by the receiving end antenna device 12, and the RF signal generator 14 is used to provide the electrical local oscillator signal required by the mixer 13. The received electrical millimeter wave / terahertz signal then enters the mixer 13 together with the local oscillator electrical signal for analog down-conversion. The intermediate frequency signal after down-conversion by the mixer 13 is amplified by the electrical amplifier 3 15, and then received by the analog-to-digital conversion device 16 (such as an oscilloscope) and digital signal processing at the receiving end is performed, which mainly includes frequency deviation and phase noise compensation and channel equalization based on pilot assistance.

[0095] Generate broadband, high-frequency electrical millimeter-wave / terahertz signals using optical heterodyne beat frequency, and change the frequency of the generated millimeter-wave / terahertz signals by tuning the wavelength difference between the two laser beams;

[0096] At the receiving end, an antenna device is used to receive the electrical millimeter wave / terahertz signal, and a mixer is used for superheterodyne reception to realize down-conversion of the electrical millimeter wave / terahertz signal. Finally, an analog-to-digital conversion device such as an oscilloscope is used for data acquisition. The digital signal processing unit at the receiving end completes the compensation of frequency deviation and phase noise by locating the position of the pilot component, low-pass filtering and phase inversion.

[0097] So far, the system has completed the generation and transmission of high-linewidth-tolerance photon-assisted terahertz / millimeter-wave signals based on RF pilot assistance.

[0098] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high linewidth tolerance photon-assisted communication system assisted by a radio frequency pilot, characterized in that: It includes a signal sending end and a signal receiving end; The signal sending end includes: A transmitting end digital signal processing unit (1) is mainly responsible for generating a single carrier or multi-carrier signal and inserting a pilot signal, wherein the single carrier scheme includes single carrier modulation and insertion of a radio frequency pilot signal; the multi-carrier scheme includes multi-carrier modulation and assigning a first subcarrier data value to a constant; Two C-band continuously tunable lasers, namely laser one (5) and laser two (8), which can be narrow-linewidth external cavity lasers or wide-linewidth distributed feedback lasers. Laser one (5) is used to generate an optical carrier of a modulated signal, and laser two (8) is used to generate a local oscillator optical signal. a digital-to-analog conversion device (2), such as an arbitrary waveform generator, for converting the digital signal generated by the digital signal processing unit into an analog baseband electrical signal; Two electrical amplifiers, namely electrical amplifier 1 (3) and electrical amplifier 2 (4), are used to amplify analog baseband electrical signals; An in-phase / quadrature optical modulator (6) for modulating a pilot-assisted single-carrier or multi-carrier electrical baseband signal onto a C-band optical carrier; A polarization-maintaining erbium-doped fiber amplifier (7) for amplifying the optical signal output by the optical modulator (6); A polarization-maintaining optical coupler (9) is used to couple the amplified optical signal with the local oscillator optical signal to generate an optical millimeter wave / terahertz signal; an optical-to-electrical converter (10) for converting an optical millimeter-wave / terahertz signal into an electrical millimeter-wave / terahertz signal; a transmitting antenna device (11) for radiating electrical millimeter wave / terahertz signals into free space; The signal receiving end includes: a receiving antenna device (12) for receiving electrical millimeter wave / terahertz signals; A radio frequency signal generator (14) for generating an electric local oscillator signal; A mixer (13) for mixing the received electrical millimeter wave / terahertz with the local oscillator electrical signal, thereby downconverting the millimeter wave / terahertz signal to a radio frequency signal range; An electrical amplifier 3 (15) for amplifying the downconverted intermediate frequency electrical signal; an analog-to-digital conversion device (16), such as an oscilloscope, for capturing the amplified electrical signal and observing the time domain and frequency spectrum of the signal; A receiving end digital signal processing unit is used to be mainly responsible for signal frequency deviation, phase noise compensation and channel equalization at the receiving end.

2. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The radio frequency pilot signal is inserted in the digital signal processing unit (1) at the transmitting end in the following manner: a single carrier directly generates a digital subcarrier in the digital domain; a multi-carrier scheme directly assigns the data of the first subcarrier to a constant, and the frequency domain is represented as a digital subcarrier located at the center of the signal.

3. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The position of the radio frequency pilot insertion in the digital signal processing unit (1) at the transmitting end is as follows: both the single-carrier and multi-carrier schemes need to reserve a guard interval. The single-carrier pilot position needs to be about 1 GHz away from the maximum component of the signal bandwidth. The specific interval size is related to the laser line width. The larger the line width, the larger the guard interval; conversely, the smaller the laser line width, the smaller the guard interval. The multi-carrier guard interval is achieved by setting the subcarriers near the first subcarrier to zero. The larger the required guard interval, the more subcarriers are set to zero.

4. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The method of frequency offset compensation is as follows: Different from the conventional digital signal processing scheme, the frequency offset compensation of single carrier and multi-carrier in the pilot-assisted scheme is realized by locating the position of the pilot component to correct the frequency offset.

5. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The compensation method for phase noise is as follows: Different from the conventional digital signal processing scheme, the compensation of single-carrier and multi-carrier phase noise in the pilot-assisted scheme is performed by extracting the phase information of the pilot component; specifically, in both the single-carrier and multi-carrier schemes, the pilot component is extracted by low-pass filtering, and then the phase of the pilot component is inverted, and finally multiplied with the time domain signal before the filter to complete the phase noise compensation.

6. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The types of lasers used in the photon-assisted scheme are: Different from the narrow-linewidth lasers, the teeth of an optical frequency comb, or the optical injection-locked optical carriers used in conventional optically generated millimeter-wave / terahertz communication schemes, the pilot-assisted scheme uses a large-linewidth, low-cost distributed feedback laser as a heterodyne optical carrier.

7. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: The pilot-assisted frequency offset and phase noise compensation scheme effectively improves the ability of the optically generated millimeter wave / terahertz system to compensate for frequency offset and phase noise, and improves the transmission performance of the system.

8. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: When two MHz-level lasers are used as heterodyne optical carriers, the transmission of signals with a bandwidth of 20 GHz and 16 / 32 / 64 quadrature amplitude-phase modulation is achieved.

9. The high linewidth tolerance photon-assisted communication system assisted by radio frequency pilot according to claim 1, characterized in that: When two distributed feedback lasers are used as heterodyne optical carriers, the generation and transmission of optical millimeter-wave / terahertz signals are realized, greatly reducing the demand for narrow-linewidth lasers in traditional optical millimeter-wave / terahertz communication system solutions.

10. A high linewidth tolerance photon-assisted communication scheme assisted by a radio frequency pilot, characterized in that: The following steps are involved: In the digital signal processing unit (1) at the transmitting end, multi-carrier or single-carrier signal generation and pilot insertion are respectively performed, and then the generated digital signal is converted into digital by using the digital-to-analog conversion device (2) to realize the generation of two baseband electrical signals of in-phase and quadrature (I / Q). The generated two baseband electrical signals are respectively amplified by the electrical amplifier 1 (3) and the electrical amplifier 2 (4) and used to drive the in-phase / quadrature optical modulator (6); the laser 1 (5) is used to generate a C-band optical carrier and then use the optical modulator (6) to generate the C-band optical carrier. ) for vector modulation; the polarization-maintaining erbium-doped optical fiber amplifier (7) is used to amplify the optical baseband signal output by the optical modulator (6); another laser second (8) is used to generate an optical local oscillator signal, and then the amplified optical signal is coupled with the polarization-maintaining erbium-doped optical amplifier (7) through a polarization-maintaining optical coupler (9) to generate an optical millimeter wave / terahertz signal, and the coupled optical millimeter wave / terahertz signal is converted into an electrical millimeter wave / terahertz signal through a photoelectric converter (10), and then radiated to free space through a transmitting end antenna device (11); At the receiving end, the transmitted electric millimeter wave / terahertz signal is received by the receiving end antenna device (12), and the radio frequency signal generator (14) is used to provide the electric local oscillator signal required by the mixer 13. The received electric millimeter wave / terahertz signal then enters the mixer (13) together with the local oscillator electric signal for analog down-conversion. The intermediate frequency signal after down-conversion by the mixer 13 is amplified by the electric amplifier three (15), and then received by the analog-to-digital conversion device (16) and digital signal processing at the receiving end is performed, which mainly includes frequency deviation and phase noise compensation and channel equalization based on pilot assistance.

Images