CN114355382A - Microwave photon MIMO radar transmitting and receiving system - Google Patents

Abstract

A microwave photonic MIMO radar transceiver system belongs to the technical field of radar detection, and solves the problems of difficulty in generating an optical frequency comb signal of a high repetition frequency at a transmitting end and a high spurious amount of a de-skewed intermediate frequency signal at a receiving end; the transmitting end generates two different repetition frequencies optical frequency comb signal, one optical frequency comb signal is used as the local oscillator optical frequency comb signal, and the other optical frequency comb signal is modulated by the baseband chirp signal as an optical carrier, and the modulated optical frequency comb signal is divided into two channels, one channel is connected with the The beat frequency of the vibrating optical frequency comb signal is used to obtain the up-converted M-channel transmission waveform, and the other channel is transmitted to the receiving subsystem as a reference optical signal; the N-channel receiving antenna at the receiving end receives the radar echo signal and modulates it to the light coupled from the transmitting subsystem. The frequency comb signal is coupled with the reference optical signal and then input to the photodetector for beat frequency, and the M×N channel de-slope intermediate frequency signal of the echo signal is obtained, and then digital signal processing is performed after analog-to-digital conversion to obtain the echo signal. target information carried in .

Description

A microwave photonic MIMO radar transceiver system

technical field

The invention belongs to the technical field of radar detection, and relates to a microwave photonic MIMO radar transceiver system.

Background technique

Radar is playing an increasingly important role in military, civil and other fields due to its excellent detection performance in extreme environments and climatic conditions. Multiple input multiple output (MIMO) radar is a new type of radar technology that has attracted much attention in recent years. Using the advantages of antenna array space diversity and waveform diversity, MIMO radar has far better overall performance than single-input single-output radar in terms of target detection, parameter estimation, imaging recognition, and anti-jamming. The traditional radar system is limited by electrical devices, and it is difficult to realize a large-bandwidth, multi-channel simultaneous transceiver integrated MIMO radar system. Microwave photonic links have the advantages of low loss, anti-electromagnetic interference, small size, and large bandwidth signal processing capabilities. In recent years, microwave photonic technology has been introduced more and more widely in modern radar systems to solve the limitations of traditional electrical devices. In the MIMO radar system, the advantages of microwave photonic technology are used to realize the generation of multi-channel orthogonal broadband radar signals, and how to realize fast real-time processing of radar echo signals due to the increase in the amount of received data. This is the current implementation scheme of MIMO radar. issues that need resolving. In the prior art, the Chinese invention patent application "Microwave Photonic MIMO Radar Detection Method and Microwave Photonic MIMO Radar System", whose application publication number is CN108287349A and whose application publication date is July 17, 2018, has the same bandwidth and chirp rate of M channels and The intermediate frequency chirp signals with non-overlapping frequencies are modulated on M channels of optical carriers with different wavelengths to generate M channels of optical signals with only positive and negative second-order sidebands; the M channels of optical signals are combined by an optical wavelength division multiplexer and divided into Divide one of them into N beams of reference light; perform photoelectric conversion on the other optical signal and separate M chirp signals that are orthogonal to each other and transmit them; use N receiving antennas to receive the target reflected signals respectively, De-slope processing and wavelength demultiplexing are performed, and photoelectric conversion, low-pass filtering and analog-to-digital conversion are performed on the obtained M optical signals respectively to obtain M×N digital signals, and the digital signals are processed to obtain the target detection result. However, this document does not solve the problems that the optical frequency comb signal with high repetition frequency in the transmitting subsystem is difficult to generate and the spurious amount of the de-slope IF signal in the receiving subsystem is high.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a microwave photonic MIMO radar transceiver system to solve the problems of difficulty in generating optical frequency comb signals with high repetition frequency in the transmitting subsystem and high spurious amount of de-slope intermediate frequency signals in the receiving subsystem.

The present invention solves the above-mentioned technical problems through the following technical solutions:

A microwave photonic MIMO radar transceiver system, comprising: a transmitting subsystem (10), a receiving subsystem (20); two optical frequency comb signals with different repetition frequencies are generated in the transmitting subsystem (10), one of which is an optical frequency comb signal As the local oscillator optical frequency comb signal, the other optical frequency comb signal is modulated by the baseband chirp signal as the optical carrier of the transmitting subsystem (10), and the modulated optical frequency comb signal is divided into two channels, one channel is connected to the local oscillator optical frequency The beat frequency of the comb signal obtains the up-converted M-channel radar transmit waveform, and the other channel is transmitted to the receiving subsystem (20) as a reference optical signal; the N-channel receiving antenna of the receiving subsystem (20) receives the radar echo signal and modulates it to transmit the waveform. The optical frequency comb signal coupled from the subsystem (10) is coupled with the reference optical signal and then input to the photodetector for beat frequency processing to obtain the M×N channel de-slope intermediate frequency signal of the radar echo signal, which is then modulated by After digital conversion, digital signal processing is performed to obtain the target information carried in the echo signal.

The microwave photonic MIMO radar transceiver system of the present invention needs to use an optical frequency comb signal with a high repetition frequency in order to realize the generation of a large bandwidth transmission signal. However, it is difficult to directly generate a high repetition frequency optical frequency comb through a simple photonic link. By using a comb filter to filter the low repetition frequency optical frequency comb signal, the frequency components of the original optical frequency comb signal are suppressed, thereby increasing the repetition frequency of the optical frequency comb. The reference optical signal at the receiving end and the modulated radar echo signal are directly coupled to one channel through an optical coupler. The optical frequency comb signal modulated by the echo signal is different from the source of the reference signal, which avoids the generation of the reference signal due to multiple modulations in the receiver. There are no extra stray light sidebands in the reference signal and echo signal in the receiver, so that the optical sideband spectrum of the reference signal and echo signal entering the photodetector for beat frequency has no other stray components, and finally suppresses to remove the spurs in the IF signal after de-slope.

Further, the emission subsystem (10) includes: a laser (301), two optical frequency combs (302), two comb filters (303), one electro-optical modulator (304), two dividing beamer (305), an optical coupler (306), an amplifier (307), an arrayed waveguide grating (308), M detectors (309) and a transmitting front end (310); the laser ( The output ends of 301) are respectively connected with the input ends of the two optical frequency combs (302), and the output ends of the two optical frequency combs (302) are respectively connected with the input ends of the two comb filters (303). The output end of the comb filter (303) is connected to the input end of the electro-optical modulator (304) of the transmitting subsystem (10), and the output end of the electro-optical modulator (304) of the transmitting subsystem (10) is connected to the first circuit The input end of the beam splitter (305) is connected, the modulated wave input port of the electro-optic modulator (304) of the transmitting subsystem (10) inputs the baseband chirp signal, and an output end of the first beam splitter (305) is connected to the transmitting The first input end of the optical coupler (306) in the subsystem (10) is connected, the other output end of the first beam splitter (305) is connected with the receiving subsystem (20), and the transmitting subsystem (10) The output terminal of the optocoupler (306) is connected to the input terminal of the amplifier (307) in the transmitting subsystem (10), and the output terminal of the amplifier (307) in the transmitting subsystem (10) is connected to the transmitting subsystem (10) The input end of the arrayed waveguide grating (308) in the transmitting subsystem (10) is connected to the M output ends of the arrayed waveguide grating (308) in the transmitting subsystem (10) respectively with the M detectors (309) in the transmitting subsystem (10). The input ends are connected, and the output ends of the M detectors (309) in the transmitting subsystem (10) are all connected with the transmitting front end (310); the output end of the second comb filter (303) is connected to the second beam splitter The input end of the second beam splitter (305) is connected to the second input end of the optical coupler (306) in the emission subsystem (10), and the second beam splitter The other output of (305) is connected to the receiving subsystem (20).

Further, the receiving subsystem (20) includes: N electro-optic modulators (304), N optical couplers (306), 1 amplifier (307), N arrayed waveguide gratings (308), M× N detectors (309) and receiving front ends (311); the outputs of the amplifiers (307) in the receiving subsystem (20) are respectively connected to the N electro-optic modulators (304) in the receiving subsystem (20) The second input ends of the N optocouplers (306) in the receiving subsystem (20) are respectively connected with the output ends of the N electro-optical modulators (304) in the receiving subsystem (20), and receive The modulated wave input ports of the N electro-optic modulators (304) in the subsystem (20) are correspondingly connected to the N output ends of the receiving front end (311), and the N optical couplers (306) in the receiving subsystem (20) are connected The output ends of the arrayed waveguide gratings (308) in the receiving subsystem (20) are respectively connected with the input ends of the N arrayed waveguide gratings (308), and the M output ends of each arrayed waveguide grating (308) in the receiving subsystem (20) are respectively connected with the receiving The input ends of the M detectors (309) in the subsystem (20) are connected; the other output ends of the beam splitter (305) in the first path are respectively connected with the N optical couplers of the receiving subsystem (20). The first input of (306) is connected. The other output end of the second beam splitter (305) is connected to the input end of the amplifier (307) in the receiving subsystem (20).

Further, the work flow of the transmitting subsystem (10): the laser (301) generates a continuous wave laser signal and is divided into two paths, which are respectively injected and locked into the two optical frequency combs (302), so that the two The optical frequency comb signals generated by the two optical frequency combs (302) are phase-coherent, the frequency intervals of the optical signals generated by the two optical frequency combs (302) are respectively FSR1 and FSR2, and the signals generated by the two optical frequency combs are respectively input to the two optical frequency combs (302). In the comb filter (303), the interval between adjacent channels of the comb filter (303) is twice the frequency interval of the optical frequency comb (302), so the optical signal generated by the optical frequency comb (302) passes through the comb filter (303) After filtering, the frequency interval becomes twice that of the original optical frequency comb; the signal after the first optical frequency comb (302) passes through the comb filter (303) is input to the transmitting subsystem (10) as an optical carrier signal In the electro-optical modulator (304) in , the optical carrier signal is modulated by a chirp signal in the electro-optical modulator. The modulated optical carrier signal is divided into two paths, one of which is input to the receiving subsystem (20) as a reference light, and the other is input to one of the input ports of the optical coupler (306) in the transmitting subsystem (10); The optical frequency comb signal generated by the two-channel optical frequency comb (302) is also divided into two channels after being filtered by the comb filter (303). One channel is input to the receiving subsystem (20) as an optical carrier signal, and the other channel is connected to the transmitter The modulated signals in the electro-optical modulator (304) in the system (10) are coupled together by an optical coupler (306) in the emission subsystem (10), and then amplified by an amplifier (307) in the emission subsystem (10) Then, it is input into the arrayed waveguide grating (308) in the transmitting subsystem (10). Different channels of the arrayed waveguide grating (308) in the emission subsystem (10) select M-channel modulation signals and optical frequency comb signals, and after photoelectric conversion by the M-channel detectors (309) in the emission subsystem (10), the obtained M channels of frequency-orthogonal chirp microwave signals are filtered and amplified, and the M channels of quadrature chirp signals are radiated to free space as transmitting signals of the radar transmitting subsystem (10).

Further, the work flow of the receiving subsystem (20): the echo signals are collected by N-way receiving antennas, and then filtered and amplified by the receiving front-end (311) and then input to the N receiving subsystems (20) respectively. At the input end of the electro-optic modulator (304), the N-channel echo signals are respectively modulated onto the optical carriers branched off after filtering by the second-channel optical frequency comb (302), and then respectively input to the N channels in the receiving subsystem (20). In the arrayed waveguide gratings (308), each echo and reference optical signal is divided into M different channels for output, and input to the detector (309) in the receiving subsystem (20) for de-skew operation to obtain M ×N channels of de-slope IF signals, and then digital signal processing after analog-to-digital conversion to obtain the target information carried in the echo signal. Both M and N are positive integers, and the sum of M and N is greater than 2.

Further, the de-slope operation is to modulate the radar echo signal on the optical carrier, and input it together with the reference light into the arrayed waveguide grating, and the corresponding optical sidebands of the echo signal and the reference optical signal are carried out in the photodetector. Beat frequency processing to obtain the difference frequency signal between the echo and the reference signal.

Further, the laser (301) is used to generate a continuous wave laser signal as the injection reference light source of the optical frequency comb (302).

Further, the comb filter (303) is composed of a plurality of passbands and stopbands periodically arranged at certain frequency intervals, and the comb filter (303) is used to filter the low repetition frequency optical frequency comb to suppress The specific frequency spectrum components in the original optical frequency comb allow the spectrum of a specific frequency to pass through, so as to realize the conversion of the low repetition frequency optical frequency comb to the high repetition frequency optical frequency comb.

Further, the electro-optical modulator (304) operates at the minimum bias point, suppresses the optical carrier signal, and only retains the modulated optical frequency comb signal of the positive and negative first-order optical sidebands.

Further, the chirp signal is generated by a digital frequency synthesizer.

The advantages of the present invention are:

The microwave photonic MIMO radar transceiver system of the present invention needs to use an optical frequency comb signal with a high repetition frequency in order to realize the generation of a large bandwidth transmission signal. However, it is difficult to directly generate a high repetition frequency optical frequency comb through a simple photonic link. By using a comb filter to filter the low repetition frequency optical frequency comb signal, the frequency components of the original optical frequency comb signal are suppressed, thereby increasing the repetition frequency of the optical frequency comb. The reference optical signal at the receiving end and the modulated radar echo signal are directly coupled to one channel through an optical coupler. The optical frequency comb signal modulated by the echo signal is different from the source of the reference signal, which avoids the generation of the reference signal due to multiple modulations in the receiver. There are no extra stray light sidebands in the reference signal and echo signal in the receiver, so that the optical sideband spectrum of the reference signal and echo signal entering the photodetector for beat frequency has no other stray components, and finally suppresses to remove the spurs in the IF signal after de-slope.

Description of drawings

Fig. 1 is a schematic diagram of an optical carrier generated by a laser being modulated by a baseband signal and a local oscillator signal;

Fig. 2 is a schematic diagram of the principle of de-slope treatment;

FIG. 3 is a schematic diagram of traditional MIMO radar echo reception;

FIG. 4 is a schematic diagram of low spurious reception of MIMO radar echoes according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a comb filter for filtering a low repetition frequency optical frequency comb.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The technical solutions of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments:

Example 1

1. Photon-assisted radar signal generation

In a radar system, parameters such as power, time width, bandwidth, and encoding form of the transmitted signal determine the detection distance, detection accuracy, and anti-jamming capability of the system. As next-generation radar systems have higher and higher requirements for detection capabilities, traditional electronic waveform generation technology has become increasingly difficult to meet the needs of radar systems. Photon-assisted signal generation is to modulate the baseband waveform generated in the electrical domain to the optical carrier through electro-optical conversion, and obtain high-order optical modulation components in the optical domain through operating point control or optical domain filtering. The up-conversion component of the baseband signal is generated after mid-demodulation, thereby multiplying the center frequency of the signal. Compared with the electronic frequency conversion scheme, the photonic frequency conversion technology has better amplitude flatness and lower phase nonlinearity.

As shown in Figure 1, the laser generates a single-frequency continuous wave laser signal, the waveform shown at point a in Figure 1, which is divided into two channels and input to the electro-optical modulator as an optical carrier signal. Modulation, the drop optical signal is modulated by the local oscillator signal, and the generated optical carrier wave has the waveforms shown at points b and c in Figure 1. The modulated baseband signal and the local oscillator signal are coupled into one channel, as shown at point d in Figure 1. After filtering by the optical filter, the waveform shown at point e in Figure 1 is selected, and the required optical sideband is selected. The local oscillator and the corresponding optical sideband of the microwave signal output by the filter are injected into the photodetector for demodulation. , and finally an up-converted microwave signal is obtained. Compared with the original baseband signal, the center frequency of the obtained RF signal can be improved several times.

2. De-oblique reception of radar echo signals

The de-slope technology uses the homodyne reception method to process the broadband chirp waveform. The de-slope IF signal can be collected by using a low-speed analog-to-digital converter, and the difficulty of subsequent signal processing is greatly reduced. In the microwave receiver, the microwave mixer is used to complete the de-slope processing of the de-slope local oscillator and the echo signal. However, the amplitude and phase characteristics of the broadband mixer are inconsistent and the intermodulation interference is difficult to eliminate, which limits the dynamic range of the de-slope system. The microwave photonic de-slope technology has the advantages of high broadband consistency and low spurious. By modulating the radar reference signal and echo signal onto the optical carrier, and using the square-law detection characteristics of the photodetector, the reference signal and echo can be obtained. The de-slope of the signal outputs an IF signal, which is similar to the de-slope result of an electrical device. The frequency of the IF signal corresponds to the distance (time delay) of the detection area one-to-one, that is, it can convert the broadband transmission signal into a narrow-band IF signal, thereby greatly reducing the requirements for the analog-to-digital converter.

As shown in Figure 2, in order to ensure the range resolution index of the radar, the transmitting waveform of the radar requires a large transmitting bandwidth, and the radar echo signal has a certain time delay t compared with the transmitting signal. It is not difficult to see that at the same time , the frequency difference f between the transmitted signal and the echo signal remains unchanged, and the frequency difference corresponds to the target distance one-to-one. In the radar receiver, if the echo signal is directly sampled and received, because of its large bandwidth, the receiver is required to have a very large sampling rate, which puts forward high requirements for the analog-to-digital converter of the receiver. The de-slope receiving process is to mix the radar transmit signal and the echo signal, so as to obtain the frequency difference between the transmit signal and the echo signal, that is, convert the wideband transmit signal into a narrowband intermediate frequency signal, and then perform the intermediate frequency signal processing. Sampling, because the frequency of the intermediate frequency signal is very low, it can be collected with a low-speed analog-to-digital converter, which reduces the amount of data after sampling.

The microwave photonic de-slope technology modulates the radar's emission signal and echo signal respectively on the optical carrier, and controls the working point of the electro-optic modulator through the DC voltage, so that the electro-optic modulator works at the minimum bias point, at this time the optical carrier and the high-order optical sideband All are suppressed, leaving only the positive and negative first-order optical sidebands modulated by the transmitted signal and the echo signal. The modulated optical carrier is filtered to retain the positive first-order optical sidebands of the emission and echo signals. The intermediate frequency signal is finally collected by the low-speed ADC for subsequent digital signal processing.

3. Typical microwave photonic radar system

As shown in Figure 3, at the transmitting end, the baseband chirp signal is modulated onto the optical carrier generated by the laser. By controlling the operating point of the dual parallel modulator, the modulator output only retains the positive and negative second-order sidebands of the chirp signal. , the modulated optical signal is divided into two channels by an optocoupler, one is input to the receiving end as a reference optical signal, the other is injected into the transmitter detector for photoelectric conversion, and the input positive and negative second-order sidebands beat each other to obtain the original chirp The quadruple frequency signal of the signal, after being amplified, is input to the transmitting antenna and radiated into free space.

At the receiving end, the receiving antenna collects the echo signal reflected by the target, and after the echo signal is amplified, it is modulated by the electro-optical modulator to the reference optical signal coupled from the transmitting end. The order sideband is filtered by an optical filter and then input to the detector for photoelectric conversion. The echo signal is de-slope processed in the detector, and finally sampled by ADC for digital signal processing.

4. Scheme of the present invention

As shown in FIG. 4, a microwave photonic MIMO radar transceiver system includes a transmitting subsystem 10 and a receiving subsystem 20; the transmitting subsystem 10 includes: a laser 301, two optical frequency combs 302, and two comb filters 303, 1 electro-optic modulator 304, 2 beam splitters 305, 1 optical coupler 306, 1 amplifier 307, 1 arrayed waveguide grating 308, M detectors 309 and transmitting front end 310; the receiving The subsystem 20 includes: N electro-optic modulators 304 , N optical couplers 306 , one amplifier 307 , N arrayed waveguide gratings 308 , M×N detectors 309 and a receiving front end 311 .

The output ends of the laser 301 are respectively connected with the input ends of the two optical frequency combs 302. The laser 301 is used to generate a continuous wave laser signal as the injection reference light source of the optical frequency comb 302. The output ends of the two optical frequency combs 302 are respectively Correspondingly connected to the input ends of the two comb filters 303, the output end of the first comb filter 303 is connected to the input end of the electro-optic modulator 304 of the emission subsystem 10, and the output end of the electro-optic modulator 304 of the emission subsystem 10 is connected. The output end is connected to the input end of the first beam splitter 305, the modulated wave input port of the electro-optical modulator 304 of the transmitting subsystem 10 inputs a baseband chirp signal, and an output end of the first beam splitter 305 is connected to the transmitting subsystem The first input end of the optical coupler 306 in 10 is connected, and the other output end of the first beam splitter 305 is respectively connected to the first input end of the N optical couplers 306 of the receiving subsystem 20, and the transmitting subsystem 10 The output terminal of the optical coupler 306 in the transmitter subsystem 10 is connected to the input terminal of the amplifier 307 in the transmitter subsystem 10, and the output terminal of the amplifier 307 in the transmitter subsystem 10 is connected to the input terminal of the arrayed waveguide grating 308 in the transmitter subsystem 10. The M output ends of the arrayed waveguide grating 308 in the transmitting subsystem 10 are respectively connected to the input ends of the M detectors 309 in the transmitting subsystem 10, and the output ends of the M detectors 309 in the transmitting subsystem 10 are all connected to the transmitting subsystem 10. The front end 310 is connected; the output end of the second comb filter 303 is connected to the input end of the second beam splitter 305, and one output end of the second beam splitter 305 is connected to the optical coupler 306 in the emission subsystem 10 The second input end of the second beam splitter 305 is connected to the input end of the amplifier 307 in the receiving subsystem 20, and the output end of the amplifier 307 in the receiving subsystem 20 is respectively connected to the receiving subsystem 20. The input terminals of the N electro-optic modulators 304 in the receiving subsystem 20 are connected to the input terminals, and the second input terminals of the N optical couplers 306 in the receiving subsystem 20 are respectively connected with the output terminals of the N electro-optic modulators 304 in the receiving subsystem 20. The modulated wave input ports of the N electro-optical modulators 304 in the subsystem 20 are correspondingly connected to the N output terminals of the receiving front end 311 , and the output terminals of the N optical couplers 306 in the receiving subsystem 20 are respectively connected to the receiving subsystem 20 . The input ends of the N arrayed waveguide gratings 308 are connected to each other, and the M output ends of each arrayed waveguide grating 308 in the receiving subsystem 20 are respectively connected to the input ends of the M detectors 309 in the receiving subsystem 20 .

How the system works

1. Emission: The laser 301 generates a continuous wave laser signal and is divided into two channels, which are injected and locked into the two optical frequency combs 302 respectively, so that the optical frequency comb signals generated by the two optical frequency combs 302 are phase-coherent, and the two optical frequency combs The frequency intervals of the optical signals generated by the comb 302 are respectively FSR1 and FSR2, and the signals generated by the two optical frequency combs are respectively input to the two comb filters 303, and the adjacent channels of the comb filters 303 are separated by the frequency of the optical frequency comb 302. Therefore, after the optical signal generated by the optical frequency comb 302 is filtered by the comb filter 303, the frequency interval becomes twice the original optical frequency comb; The signal is input to the electro-optical modulator 304 in the transmit subsystem 10 as an optical carrier signal, where the optical carrier signal is modulated by a chirp signal. The modulated optical carrier signal is divided into two channels, one of which is input to the receiving subsystem 20 as a reference light, and the other is input to one of the input ports of the optical coupler 306 in the transmitting subsystem 10; the second optical frequency comb 302 The generated optical frequency comb signal is also divided into two paths after being filtered by the comb filter 303, one path is input to the receiving subsystem 20 as an optical carrier signal, and the other path is connected to the modulated signal in the electro-optical modulator 304 in the transmitting subsystem 10. They are coupled together by the optical coupler 306 in the transmitting subsystem 10 , and then amplified by the amplifier 307 in the transmitting subsystem 10 , and then input to the arrayed waveguide grating 308 in the transmitting subsystem 10 . Different channels of the arrayed waveguide grating 308 in the emission subsystem 10 select M channels of modulation signals and optical frequency comb signals, and after photoelectric conversion by the M channels of detectors 309 in the emission subsystem 10, M channels of orthogonal frequency linear frequency modulation are obtained The microwave signal and the M-channel quadrature chirp signal are filtered and amplified and radiated to the free space as the transmit signal of the radar transmitting subsystem 10 .

As shown in FIG. 5 , the comb filter 303 is composed of a plurality of passbands and stopbands periodically arranged at certain frequency intervals. The comb filter 303 is used to filter the low repetition frequency optical frequency comb to suppress the original Some frequency spectral components in the optical frequency comb allow the spectrum of a specific frequency to pass through, so as to realize the conversion of the low repetition frequency optical frequency comb to the high repetition frequency optical frequency comb. The optical frequency comb 302 is spectrally filtered by the comb filter 303, which doubles the repetition frequency of the optical frequency comb 302 signal, and solves the problem that the optical frequency comb signal with high repetition frequency is difficult to generate.

The electro-optic modulator 304 operates at the minimum bias point, suppresses the optical carrier signal, and only retains the modulated optical frequency comb signal of the positive and negative first-order optical sidebands. The chirp signal is generated by a digital frequency synthesizer.

2. Reception: The echo signals are collected by N channels of receiving antennas, filtered and amplified by the receiving front end 311, and then input to the input ends of the N electro-optical modulators 304 in the receiving subsystem 20, respectively, and the N channels of echo signals are modulated to The second channel of optical frequency comb 302 is filtered and branched from the optical carrier, and then input to the N arrayed waveguide gratings 308 in the receiving subsystem 20 respectively, and each channel of echo and reference optical signal is divided into M channels of different channels output, and input it to the detector 309 in the receiving subsystem 20 for de-slope operation to obtain M×N de-slope intermediate frequency signals, and then perform digital signal processing after analog-to-digital conversion to obtain the target information carried in the echo signal. . Both M and N are positive integers, and the sum of M and N is greater than 2. The de-slope operation is to modulate the radar echo signal on the optical carrier and input it together with the reference light to the arrayed waveguide grating, and the corresponding optical sidebands of the echo signal and the reference optical signal are beat frequency processed in the photodetector. , the difference frequency signal between the echo and the reference signal is obtained. The reference signal at the receiving end is not modulated by the echo signal, and no new high-order modulation component is added to the reference signal. Finally, the spur of the de-slope IF signal in the receiver can be effectively suppressed.

The invention provides a microwave photonic MIMO radar transceiver system. The transmitter generates two optical frequency comb signals with different repetition frequencies, one of which is used as a local oscillator optical frequency comb, and the other optical frequency comb is used as an optical carrier to be modulated by a baseband chirp signal. The modulated optical frequency comb Divided into two channels, one channel and the local oscillator optical frequency comb beat frequency to obtain the up-converted M channel radar transmit waveform, and the other channel is transmitted to the receiving end as a reference optical signal; the N channel receiving antenna at the receiving end receives the radar echo signal and modulates it to The optical frequency comb coupled from the transmitting end is coupled with the reference optical signal and then input to the photoelectric detector for beat frequency processing to obtain the de-slope intermediate frequency signal of the radar echo signal. Finally, M×N digital signals are obtained after sampling by the analog-to-digital converter, and subsequent digital signal processing is performed to obtain the target information carried in the radar echo.

In the traditional MIMO radar receiving scheme, the radar echo signal directly modulates the optical reference signal, and the modulated signal is input to the detector for de-skew reception, and an intermediate frequency signal is obtained (the reference optical signal has been modulated once at the transmitting end, and at the receiving end. After the modulation of the radar echo signal again, it is easy to generate unnecessary high-order modulation components). In the radar echo signal receiving scheme proposed by the solution of the present invention, the radar echo signal is modulated onto the optical carrier signal, and then coupled to the reference optical signal through an optical coupler. The high-order modulation optical sidebands generated by the sub-modulation can suppress the spurs introduced by the high-order sidebands in the IF signal.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. a microwave photon MIMO radar transceiver system, is characterized in that, comprises: transmitting subsystem (10), receiving subsystem (20); In the transmitting subsystem (10), the optical frequency comb signal of two different repetition frequencies is generated, One of the optical frequency comb signals is used as the local oscillator optical frequency comb signal, and the other optical frequency comb signal is modulated by the baseband chirp signal as the optical carrier of the transmitting subsystem (10), and the modulated optical frequency comb signal is divided into two channels, One channel beats the local oscillator optical frequency comb signal to obtain up-converted M channels of transmission waveforms, and the other channel is transmitted to the receiving subsystem (20) as a reference optical signal; the N channels of the receiving antenna of the receiving subsystem (20) receive the echo signals Then, it is modulated to the optical frequency comb signal coupled from the emission subsystem (10), coupled with the reference optical signal, and then input to the photodetector for beat frequency processing to obtain the M×N channel de-slope intermediate frequency signal of the echo signal, After analog-to-digital conversion, digital signal processing is performed to obtain the target information carried in the echo signal. 2. A microwave photonic MIMO radar transceiver system according to claim 1, wherein the transmitting subsystem (10) comprises: a laser (301), two optical frequency combs (302), two combs A filter (303), an electro-optical modulator (304), two beam splitters (305), an optical coupler (306), an amplifier (307), an arrayed waveguide grating (308), M detectors (309) and a transmitting front end (310); the output ends of the laser (301) are respectively connected with the input ends of the two optical frequency combs (302), and the output ends of the two optical frequency combs (302) are respectively connected with the input ends of the two comb filters (303) correspondingly, and the output end of the first comb filter (303) is connected with the input end of the electro-optical modulator (304) of the emission subsystem (10), and transmits The output end of the electro-optic modulator (304) of the subsystem (10) is connected to the input end of the first beam splitter (305), and the modulated wave input port of the electro-optic modulator (304) of the emission subsystem (10) is input to the baseband Linear frequency modulation signal, one output end of the first beam splitter (305) is connected to the first input end of the optical coupler (306) in the transmitting subsystem (10), and the other end of the first beam splitter (305) is connected One output terminal is connected to the receiving subsystem (20), the output terminal of the optocoupler (306) in the transmitting subsystem (10) is connected to the input terminal of the amplifier (307) in the transmitting subsystem (10), and the transmitting subsystem (10) The output end of the amplifier (307) in (10) is connected to the input end of the arrayed waveguide grating (308) in the transmitting subsystem (10), and M outputs of the arrayed waveguide grating (308) in the transmitting subsystem (10) The terminals are respectively connected with the input terminals of the M detectors (309) in the transmitting subsystem (10), and the output terminals of the M detectors (309) in the transmitting subsystem (10) are all connected with the transmitting front end (310); The output end of the second comb filter (303) is connected to the input end of the second beam splitter (305), and one output end of the second beam splitter (305) is connected to the input end of the second beam splitter (305). The second input end of the optical coupler (306) is connected, and the other output end of the second beam splitter (305) is connected with the receiving subsystem (20). 3. A microwave photonic MIMO radar transceiver system according to claim 2, wherein the receiving subsystem (20) comprises: N electro-optical modulators (304), N optical couplers (306) , an amplifier (307), N arrayed waveguide gratings (308), M×N detectors (309) and a receiving front end (311); the output of the amplifier (307) in the receiving subsystem (20) The terminals are respectively connected to the input terminals of the N electro-optic modulators (304) in the receiving subsystem (20), and the second input terminals of the N optical couplers (306) in the receiving subsystem (20) are respectively connected to the receiving subsystem (20). The outputs of the N electro-optic modulators (304) in (20) are connected, and the modulated wave input ports of the N electro-optic modulators (304) in the receiving subsystem (20) correspond to the N outputs of the receiving front end (311). The output ends of the N optical couplers (306) in the receiving subsystem (20) are respectively connected with the input ends of the N arrayed waveguide gratings (308) in the receiving subsystem (20), and the receiving subsystem (20) The M output ends of each arrayed waveguide grating (308) in ) are respectively connected with the input ends of the M detectors (309) in the receiving subsystem (20); the beam splitter (305) in the first channel The other output terminals of the N optical couplers (306) are respectively connected to the first input terminals of the N optical couplers (306) of the receiving subsystem (20). The other output end of the second beam splitter (305) is connected to the input end of the amplifier (307) in the receiving subsystem (20). 4. A microwave photonic MIMO radar transceiver system according to claim 3, characterized in that, the work flow of the transmitting subsystem (10): the laser (301) generates a continuous wave laser signal and is divided into The two channels are respectively injected and locked into the two optical frequency combs (302), so that the optical frequency comb signals generated by the two optical frequency combs (302) are phase-coherent, and the optical signals generated by the two optical frequency combs (302) are separated in frequency. They are FSR1 and FSR2 respectively, and the signals generated by the two optical frequency combs are respectively input into two comb filters (303), and the interval between adjacent channels of the comb filters (303) is equal to the frequency interval of the optical frequency comb (302). Therefore, after the optical signal generated by the optical frequency comb (302) is filtered by the comb filter (303), the frequency interval becomes twice that of the original optical frequency comb; the first optical frequency comb (302) is comb-filtered The signal after the device (303) is input to the electro-optical modulator (304) in the transmitting subsystem (10) as an optical carrier signal, where the optical carrier signal is modulated by a chirp signal. The modulated optical carrier signal is divided into two paths, one of which is input to the receiving subsystem (20) as a reference light, and the other is input to one of the input ports of the optical coupler (306) in the transmitting subsystem (10); The optical frequency comb signal generated by the two-channel optical frequency comb (302) is also divided into two channels after being filtered by the comb filter (303). One channel is input to the receiving subsystem (20) as an optical carrier signal, and the other channel is connected to the transmitter The modulated signals in the electro-optical modulator (304) in the system (10) are coupled together by an optical coupler (306) in the emission subsystem (10), and then amplified by an amplifier (307) in the emission subsystem (10) Then, it is input into the arrayed waveguide grating (308) in the transmitting subsystem (10). Different channels of the arrayed waveguide grating (308) in the emission subsystem (10) select M-channel modulation signals and optical frequency comb signals, and after photoelectric conversion by the M-channel detectors (309) in the emission subsystem (10), the obtained M channels of frequency-orthogonal chirp microwave signals are filtered and amplified, and the M channels of quadrature chirp signals are radiated to free space as transmitting signals of the radar transmitting subsystem (10). 5. A kind of microwave photonic MIMO radar transceiver system according to claim 4, is characterized in that, the work flow of described receiving subsystem (20): echo signal is collected through N way receiving antenna, and then through receiving front end ( 311) After filtering and amplifying, they are respectively input to the input ends of the N electro-optical modulators (304) in the receiving subsystem (20), and the N-path echo signals are respectively modulated to the second-path optical frequency comb (302) and then split after filtering. The incoming optical carrier is then respectively input to the N arrayed waveguide gratings (308) in the receiving subsystem (20), and each echo and reference optical signal is divided into M different channels for output, and input to the receiving sub-system (20). The detector (309) in the system (20) performs a de-skew operation to obtain M×N channels of de-skew intermediate frequency signals, and then performs digital signal processing after analog-to-digital conversion to obtain the target information carried in the echo signal. Both M and N are positive integers, and the sum of M and N is greater than 2. 6 . A microwave photonic MIMO radar transceiver system according to claim 5 , wherein the de-slope operation is to modulate the radar echo signal onto an optical carrier, and input it to the arrayed waveguide grating together with the reference light. 7 . , the corresponding optical sidebands of the echo signal and the reference optical signal are subjected to beat frequency processing in the photodetector to obtain the difference frequency signal of the echo and the reference signal. 7 . The microwave photonic MIMO radar transceiver system according to claim 2 , wherein the laser ( 301 ) is used to generate a continuous wave laser signal as an injection reference light source of the optical frequency comb ( 302 ). 8 . 8. A microwave photonic MIMO radar transceiver system according to claim 2, wherein the comb filter (303) is composed of a plurality of passbands and stopbands periodically arranged at certain frequency intervals, The low repetition frequency optical frequency comb is filtered by the comb filter (303), the specific frequency spectrum components in the original optical frequency comb are suppressed, and the spectrum of the specific frequency is allowed to pass through, so as to realize the low repetition frequency optical frequency comb to the high repetition frequency light Conversion of frequency combs. 9. A microwave photonic MIMO radar transceiver system according to claim 2, characterized in that the electro-optical modulator (304) operates at the minimum bias point, suppresses the optical carrier signal, and only retains positive and negative first-order light Sideband modulated optical frequency comb signal. 10 . The microwave photonic MIMO radar transceiver system according to claim 4 , wherein the chirp signal is generated by a digital frequency synthesizer. 11 .

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