CN114355382A - Microwave photon MIMO radar transmitting and receiving system - Google Patents
Microwave photon MIMO radar transmitting and receiving system Download PDFInfo
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Abstract
A microwave photon MIMO radar receiving and transmitting system belongs to the technical field of radar detection and solves the problems that a high-repetition-frequency optical frequency comb signal at a transmitting end is difficult to generate and stray quantity of a declivity intermediate frequency signal at a receiving end is high; the transmitting end generates two optical frequency comb signals with different repetition frequencies, one optical frequency comb signal serves as a local oscillator optical frequency comb signal, the other optical frequency comb signal serves as an optical carrier and is modulated by a baseband linear frequency modulation signal, the modulated optical frequency comb signal is divided into two paths, one path is subjected to frequency beating with the local oscillator optical frequency comb signal to obtain M paths of up-conversion transmitting waveforms, and the other path is transmitted to the receiving subsystem to serve as a reference optical signal; the receiving end N-path receiving antenna receives radar echo signals, modulates the radar echo signals to optical frequency comb signals coupled by the transmitting subsystem, couples the radar echo signals with reference optical signals, inputs the radar echo signals into a photoelectric detector for frequency beating to obtain MXN-path deskew intermediate frequency signals of the echo signals, and processes digital signals after analog-to-digital conversion to obtain target information carried in the echo signals.
Description
Technical Field
The invention belongs to the technical field of radar detection, and relates to a microwave photon MIMO radar transmitting and receiving system.
Background
The radar still keeps excellent detection performance under extreme environment and weather conditions, and plays an increasingly large role in various fields such as military, civil use and the like. Multiple Input Multiple Output (MIMO) radar is a new radar technology that has attracted attention in recent years. The MIMO radar utilizes the advantages of antenna array space diversity and waveform diversity, and has overall performance far superior to that of a single-input single-output system radar in the aspects of target detection, parameter estimation, imaging identification, interference resistance and the like. The traditional radar system is limited by electrical devices, and is difficult to realize a large-bandwidth multi-channel MIMO radar system capable of receiving and transmitting simultaneously. The microwave photon link has the advantages of low loss, electromagnetic interference resistance and small size, and simultaneously has large-bandwidth signal processing capacity, so that the microwave photon technology is more and more widely introduced into modern radar systems in recent years to solve the limitation of the traditional electrical devices. The advantages of the microwave photon technology are utilized in the MIMO radar system, the generation of multi-path orthogonal broadband radar signals is realized, and how to realize the rapid real-time processing of radar echo signals due to the increase of the received data volume is the problem to be solved in the current MIMO radar implementation scheme. In the prior art, in the chinese patent application of microwave photonic MIMO radar detection method and microwave photonic MIMO radar system, which is published under the application publication number CN108287349A and published under the application publication number 2018, number 07, 17, M channels of intermediate frequency linear frequency modulation signals with the same bandwidth and chirp rate and mutually non-overlapping frequencies are modulated on M channels of optical carriers with different wavelengths, so as to generate M channels of optical signals only retaining positive and negative second-order sidebands; the M paths of optical signals are combined by an optical wavelength division multiplexer and then divided into two paths; dividing one path of the reference light into N beams of reference light; performing photoelectric conversion on the other path of optical signal and separating M linear frequency modulation signals which are orthogonal to each other from the other path of optical signal to be transmitted; and respectively receiving the target reflection signals by using N receiving antennas, performing deskew processing and wavelength demultiplexing, respectively performing photoelectric conversion, low-pass filtering and analog-to-digital conversion on the obtained M paths of optical signals to obtain M multiplied by N paths of digital signals, and processing the digital signals to obtain a target detection result. However, the document does not solve the problem that the optical frequency comb signal with high repetition frequency in the transmitting subsystem is difficult to generate and the stray amount of the deskew intermediate frequency signal in the receiving subsystem is high.
Disclosure of Invention
The invention aims to provide a microwave photon MIMO radar receiving and transmitting system, which aims to solve the problems that optical frequency comb signals with high repetition frequency in a transmitting subsystem are difficult to generate and the stray quantity of deskew intermediate frequency signals in a receiving subsystem is high.
The invention solves the technical problems through the following technical scheme:
a microwave photonic MIMO radar transceiver system comprising: a transmitting subsystem (10) and a receiving subsystem (20); generating two optical frequency comb signals with different repetition frequencies in a transmitting subsystem (10), wherein one optical frequency comb signal is used as a local oscillator optical frequency comb signal, the other optical frequency comb signal is used as an optical carrier of the transmitting subsystem (10) and is modulated by a baseband linear frequency modulation signal, the modulated optical frequency comb signal is divided into two paths, one path is subjected to frequency beating with the local oscillator optical frequency comb signal to obtain M paths of radar transmitting waveforms of up-conversion, and the other path is transmitted to a receiving subsystem (20) to be used as a reference optical signal; n paths of receiving antennas of the receiving subsystem (20) receive radar echo signals, then modulate the radar echo signals onto optical frequency comb signals coupled by the transmitting subsystem (10), couple the radar echo signals with reference optical signals, then input the radar echo signals into a photoelectric detector to carry out beat frequency processing to obtain MXN paths of deskew intermediate frequency signals of the radar echo signals, and then carry out digital signal processing after analog-to-digital conversion to obtain target information carried in the echo signals.
In order to realize the generation of a large-bandwidth transmitting signal, the transmitting end of the microwave photon MIMO radar transmitting-receiving system needs to adopt an optical frequency comb signal with high repetition frequency, however, the optical frequency comb with high repetition frequency is difficult to directly generate through a simple photon link. The reference optical signal of the receiving end and the modulated radar echo signal are directly coupled to one path through the optical coupler, the optical frequency comb signal modulated by the echo signal has different reference signal sources, so that high-order optical sideband components of the reference signal generated in the receiver due to multiple modulation are avoided, the reference signal and the echo signal in the receiver have no redundant stray optical sideband, the optical sideband spectrum of the reference signal and the echo signal entering the photoelectric detector for beat frequency has no other stray components, and finally, the stray in the intermediate frequency signal after deskew is restrained.
Further, the transmitting subsystem (10) comprises: a laser (301), 2 optical-frequency combs (302), 2 comb filters (303), 1 electro-optical modulator (304), 2 beam splitters (305), 1 optical coupler (306), 1 amplifier (307), 1 arrayed waveguide grating (308), M detectors (309), and a transmit front end (310); the output end of the laser (301) is respectively connected with the input ends of the 2 optical frequency combs (302), the output end of the 2 optical frequency combs (302) is respectively correspondingly connected with the input ends of the 2 comb filters (303), the output end of the first comb filter (303) is connected with the input end of the electro-optical modulator (304) of the transmitting subsystem (10), the output end of the electro-optical modulator (304) of the transmitting subsystem (10) is connected with the input end of the first beam splitter (305), the modulation wave input port of the electro-optical modulator (304) of the transmitting subsystem (10) inputs a baseband chirp signal, one output end of the first beam splitter (305) is connected with the first input end of the optical coupler (306) in the transmitting subsystem (10), the other output end of the first beam splitter (305) is connected with the receiving subsystem (20), the output end of the optical coupler (306) in the transmitting subsystem (10) is connected with the output end of the amplifier (307) in the transmitting subsystem (10) The input end of the amplifier (307) in the emission subsystem (10) is connected, the output end of the amplifier (307) in the emission subsystem (10) is connected with the input end of the arrayed waveguide grating (308) in the emission subsystem (10), M output ends of the arrayed waveguide grating (308) in the emission subsystem (10) are respectively connected with the input ends of M detectors (309) in the emission subsystem (10), and the output ends of the M detectors (309) in the emission subsystem (10) are connected with the emission front end (310); the output end of the second path comb filter (303) is connected with the input end of a second path beam splitter (305), one output end of the second path beam splitter (305) is connected with the second input end of an optical coupler (306) in the transmitting subsystem (10), and the other output end of the second path beam splitter (305) is connected with the receiving subsystem (20).
Further, the receiving subsystem (20) comprises: n electro-optical modulators (304), N optical couplers (306), 1 amplifier (307), N arrayed waveguide gratings (308), M N detectors (309), and a receive front end (311); the output ends of the amplifiers (307) in the receiving subsystem (20) are respectively connected with the input ends of the N electro-optical modulators (304) in the receiving subsystem (20), the second input ends of N optical couplers (306) in the receiving subsystem (20) are respectively connected with the output ends of N electro-optical modulators (304) in the receiving subsystem (20), the modulated wave input ports of the N electro-optical modulators (304) in the receiving subsystem (20) are correspondingly connected with N output ends of a 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 N arrayed waveguide gratings (308) in the receiving subsystem (20), m output ends of each arrayed waveguide grating (308) in the receiving subsystem (20) are respectively connected with input ends of M detectors (309) in the receiving subsystem (20); the other output end of the first path of the beam splitter (305) is respectively connected with the first input end of the N optical couplers (306) of the receiving subsystem (20). The other output terminal of the second path of said beam splitter (305) is connected to the input terminal of an amplifier (307) in the receiving subsystem (20).
Further, the work flow of the transmitting subsystem (10) is as follows: the laser (301) generates continuous wave laser signals and is divided into two paths, the two paths are respectively injected and locked into 2 optical frequency combs (302), the phases of the optical frequency comb signals generated by the 2 optical frequency combs (302) are coherent, the frequency intervals of the optical signals generated by the 2 optical frequency combs (302) are FSR1 and FSR2 respectively, the signals generated by the 2 optical frequency combs are respectively input into the 2 comb filters (303), the adjacent channel interval of the comb filters (303) is twice of the frequency interval of the optical frequency combs (302), therefore, the frequency interval is twice of the original optical frequency comb after the optical signals generated by the optical frequency combs (302) are filtered by the comb filters (303); the signal of the first optical comb (302) after passing through the comb filter (303) is input to an electro-optical modulator (304) in the transmitting subsystem (10) as an optical carrier signal, and 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, wherein one path is used as reference light and input into a receiving subsystem (20), and the other path is input into one input port of an optical coupler (306) in a transmitting subsystem (10); an optical frequency comb signal generated by the second optical frequency comb (302) is filtered by the comb filter (303) and then is also divided into two paths, one path is used as an optical carrier signal and is input into the receiving subsystem (20), the other path is coupled with a modulated signal in the electro-optical modulator (304) in the transmitting subsystem (10) through the optical coupler (306) in the transmitting subsystem (10), and the other path is amplified by the amplifier (307) in the transmitting subsystem (10) and then is input into the arrayed waveguide grating (308) in the transmitting subsystem (10). M paths of modulation signals and optical frequency comb signals are selected from different channels of the arrayed waveguide grating (308) in the transmitting subsystem (10), M paths of linear frequency modulation microwave signals with orthogonal frequencies are obtained after photoelectric conversion of M paths of detectors (309) in the transmitting subsystem (10), and the M paths of orthogonal linear frequency modulation microwave signals are used as transmitting signals of the radar transmitting subsystem (10) to be radiated to a free space after being filtered and amplified.
Further, the work flow of the receiving subsystem (20) is as follows: echo signals are collected by N paths of receiving antennas, filtered and amplified by a receiving front end (311) and then respectively input to input ends of N electro-optical modulators (304) in a receiving subsystem (20), the N paths of echo signals are respectively modulated onto optical carriers which are filtered and then split by a second path of optical frequency comb (302), and then are respectively input into N array waveguide gratings (308) in the receiving subsystem (20), each path of echo and reference optical signals are divided into M paths of different channels to be output, and are input into a detector (309) in the receiving subsystem (20) to be subjected to deskew operation, M multiplied by N paths of deskew intermediate frequency signals are obtained, digital signal processing is performed after analog-to-digital conversion, and target information carried in the echo signals is obtained. M, N are positive integers, and the sum of M and N is more than 2.
Furthermore, the deskew operation is to modulate a radar echo signal onto an optical carrier, and input the modulated radar echo signal and reference light into the arrayed waveguide grating together, and perform beat frequency processing on corresponding optical sidebands of the echo signal and the reference light signal in a photoelectric detector to obtain a difference frequency signal of the echo and the reference signal.
Further, the laser (301) is used for generating a continuous wave laser signal as an injection reference light source of the optical frequency comb (302).
Furthermore, the comb filter (303) is composed of a plurality of pass bands and stop bands which are periodically arranged at certain frequency intervals, the low-repetition-frequency optical frequency comb is filtered by the comb filter (303), specific frequency spectrum components in the original optical frequency comb are restrained, and a spectrum of specific frequency is allowed to pass, so that the conversion from the low-repetition-frequency optical frequency comb to the high-repetition-frequency optical frequency comb is realized.
Further, the electro-optic modulator (304) operates at a minimum bias point to suppress the optical carrier signal and to retain only 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 invention has the advantages that:
in order to realize the generation of a large-bandwidth transmitting signal, the transmitting end of the microwave photon MIMO radar transmitting-receiving system needs to adopt an optical frequency comb signal with high repetition frequency, however, the optical frequency comb with high repetition frequency is difficult to directly generate through a simple photon link. The reference optical signal of the receiving end and the modulated radar echo signal are directly coupled to one path through the optical coupler, the optical frequency comb signal modulated by the echo signal has different reference signal sources, so that high-order optical sideband components of the reference signal generated in the receiver due to multiple modulation are avoided, the reference signal and the echo signal in the receiver have no redundant stray optical sideband, the optical sideband spectrum of the reference signal and the echo signal entering the photoelectric detector for beat frequency has no other stray components, and finally, the stray in the intermediate frequency signal after deskew is restrained.
Drawings
Fig. 1 is a schematic diagram of an optical carrier generated by a laser modulated by a baseband signal and a local oscillator signal;
FIG. 2 is a schematic diagram of the principle of deskewing;
FIG. 3 is a diagram illustrating conventional MIMO radar echo reception;
FIG. 4 is a diagram illustrating low spurious reception of an MIMO radar echo according to an embodiment of the present invention;
fig. 5 is a diagram illustrating the filtering of the low-repetition-frequency optical comb by the comb filter.
Detailed Description
In order to make the objects, 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 with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is further described by combining the drawings and the specific embodiments in the specification:
example one
1. Photonic assisted radar signal generation
In a radar system, parameters such as power, time width, bandwidth and coding form of a transmitted signal determine the detection distance, detection precision and anti-interference capability of the system. With the higher and higher requirements of the next generation radar system on the detection capability, the conventional electronic waveform generation technology has been more and more difficult to meet the requirements of the radar system. The photon auxiliary signal generation is to modulate a baseband waveform generated by an electric domain onto an optical carrier through electro-optical conversion, obtain a high-order optical modulation component in an optical domain through modes of working point control, optical domain filtering and the like, and generate an up-conversion component of a baseband signal after the modulation component and a local oscillation signal are demodulated in a photoelectric detector, so that the central frequency of the signal is multiplied. Compared with an electronic frequency conversion scheme, the photon frequency conversion technology has better amplitude flatness and lower phase nonlinearity.
As shown in fig. 1, a laser generates a single-frequency continuous wave laser signal, a waveform shown as a point a in fig. 1 is divided into two paths and input into an electro-optical modulator as an optical carrier signal, where an upper optical carrier is modulated by a baseband microwave signal, a lower optical signal is modulated by a local oscillator signal, the generated optical carriers have waveforms shown as b and c in fig. 1, the modulated baseband signal and the local oscillator signal are coupled into one path, a waveform shown as a point d in fig. 1 is filtered by an optical filter, and then a desired optical sideband is selected as a waveform shown as a point e in fig. 1, the local oscillator output by the filter and the corresponding optical sideband of the microwave signal are injected into an optical photodetector for demodulation, and finally an up-conversion microwave signal is obtained.
2. Radar echo signal deskew reception
The deskew technology is used for processing a broadband linear frequency modulation waveform in a homodyne receiving mode, and a deskew intermediate-frequency signal can be acquired by adopting a low-speed analog-to-digital converter, so that the difficulty of subsequent signal processing is greatly reduced. In the microwave receiver, a microwave mixer is adopted to finish the deskew processing of deskew local oscillation signals and echo signals, but the amplitude-phase characteristics of the broadband mixer are inconsistent, intermodulation interference is difficult to eliminate, and the dynamic range of a deskew system is limited. The microwave photon deskew technology has the advantages of high broadband consistency and low stray, a reference signal and an echo signal of a radar are modulated onto an optical carrier, the square-law detection characteristic of a photoelectric detector is utilized, a deskew output intermediate frequency signal of the reference signal and the echo signal can be obtained, the deskew output intermediate frequency signal is similar to a deskew result of an electrical device, the frequency of the intermediate frequency signal corresponds to the distance (time delay) of a detection area one to one, namely, a transmitting signal of a broadband can be converted into the intermediate frequency signal of the narrowband, and therefore the requirement on a digital-to-analog converter is greatly reduced.
As shown in fig. 2, in order to ensure the range resolution index of the radar, the transmitting waveform of the radar is required to have a large transmitting bandwidth, and the radar echo signal has a certain time delay t compared with the transmitting signal, it is easy to see that, at the same time, the frequency difference f between the transmitting signal and the echo signal is constant, and the frequency difference corresponds to the target distance one by one. In a radar receiver, if echo signals are directly sampled and received, the receiver is required to have a very large sampling rate due to the very large bandwidth, and a very high requirement is put on an analog-to-digital converter of the receiver. The deskew receiving processing is to perform frequency mixing processing on a radar transmitting signal and an echo signal so as to obtain the frequency difference between the transmitting signal and the echo signal, namely, the transmitting signal of a broadband is converted into a narrowband intermediate frequency signal, and then the intermediate frequency signal is sampled.
The microwave photon deskew technology modulates a transmitting signal and an echo signal of a radar onto an optical carrier respectively, controls a working point of an electro-optical modulator through direct current voltage, enables the electro-optical modulator to work at a minimum bias point, inhibits both the optical carrier and a high-order optical sideband at the moment, and only leaves a positive-negative first-order optical sideband after the transmitting signal and the echo signal are modulated. The modulated optical carrier is filtered and then reserves a positive first-order optical sideband of the transmitting and echo signals, the positive first-order sideband of the transmitting signal and the positive first-order sideband of the echo signal are subjected to beat frequency in a photoelectric detector to obtain an intermediate frequency signal after the two sidebands are subjected to frequency mixing, and finally, the intermediate frequency signal is acquired by a low-speed ADC and then is subjected to subsequent digital signal processing.
3. Typical microwave photon radar system
As shown in fig. 3, at the transmitting end, the baseband chirp signal is modulated onto the optical carrier generated by the laser, the operating point of the dual-parallel modulator is controlled to make the output end of the modulator only retain the positive and negative second-order sidebands of the chirp signal, the modulated optical signal is divided into two paths by the optical coupler, one path is input to the receiving end as the reference optical signal, the other path is injected to the detector at the transmitting end for photoelectric conversion, the input positive and negative second-order sidebands beat each other to obtain the quadruple frequency signal of the original chirp signal, and the quadruple frequency signal is amplified and then input to the transmitting antenna to be radiated to the free space.
At a receiving end, a receiving antenna collects echo signals reflected by a target, the echo signals are modulated onto reference light signals coupled by a transmitting end through an electro-optical modulator after being amplified, unnecessary high-order sidebands can be generated due to the fact that the reference signals are subjected to echo modulation again, the high-order sidebands are input into a detector for photoelectric conversion after being filtered by an optical filter, the echo signals are subjected to deskew processing in the detector, and finally digital signal processing is carried out after sampling by an ADC.
4. Aspects of the invention
As shown in fig. 4, a microwave photonic MIMO radar transceiving system includes a transmitting subsystem 10 and a receiving subsystem 20; the transmitting subsystem 10 includes: a laser 301, 2 optical-frequency combs 302, 2 comb filters 303, 1 electro-optical modulator 304, 2 beam splitters 305, 1 optical coupler 306, 1 amplifier 307, 1 arrayed waveguide grating 308, M detectors 309, and a transmit front end 310; the receiving subsystem 20 includes: n electro-optical modulators 304, N optical couplers 306, 1 amplifier 307, N arrayed waveguide gratings 308, M × N detectors 309, and a receive front-end 311.
The output end of the laser 301 is connected to the input ends of the 2 optical frequency combs 302, the laser 301 is configured to generate a continuous wave laser signal as an injection reference light source of the optical frequency combs 302, the output ends of the 2 optical frequency combs 302 are correspondingly connected to the input ends of the 2 comb filters 303, the output end of the first comb filter 303 is connected to the input end of the electro-optical modulator 304 of the transmitting subsystem 10, the output end of the electro-optical modulator 304 of the transmitting subsystem 10 is connected to the input end of the first beam splitter 305, a modulation wave input port of the electro-optical modulator 304 of the transmitting subsystem 10 inputs a baseband chirp signal, one output end of the first beam splitter 305 is connected to the first input end of the optical coupler 306 of the transmitting subsystem 10, and the other output end of the first beam splitter 305 is connected to the first input ends of the N optical couplers 306 of the receiving subsystem 20, the output end of the optical coupler 306 in the transmitting subsystem 10 is connected with the input end of the amplifier 307 in the transmitting subsystem 10, the output end of the amplifier 307 in the transmitting subsystem 10 is connected with the input end of the arrayed waveguide grating 308 in the transmitting subsystem 10, M output ends of the arrayed waveguide grating 308 in the transmitting subsystem 10 are respectively connected with the input ends of 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 with the transmitting front end 310; the output end of the second-way comb filter 303 is connected to the input end of the second-way beam splitter 305, one output end of the second-way beam splitter 305 is connected to the second input end of the optical coupler 306 in the transmitting subsystem 10, the other output end of the second-way beam splitter 305 is connected to the input end of the amplifier 307 in the receiving subsystem 20, the output ends of the amplifier 307 in the receiving subsystem 20 are respectively connected to the input ends of the N electro-optical modulators 304 in the receiving subsystem 20, the second input ends of the N optical couplers 306 in the receiving subsystem 20 are respectively connected to the output ends of the N electro-optical modulators 304 in the receiving subsystem 20, the modulated wave input ports of the N electro-optical modulators 304 in the receiving subsystem 20 are correspondingly connected to the N output ends of the receiving front end 311, the output ends of the N optical couplers 306 in the receiving subsystem 20 are respectively connected to the input ends of the N arrayed waveguide gratings 308 in the receiving subsystem 20, the M outputs of each arrayed waveguide grating 308 in the receiving subsystem 20 are connected to the inputs of the M detectors 309 in the receiving subsystem 20, respectively.
Working principle of system
1. Emission: the laser 301 generates a continuous wave laser signal and is divided into two paths, the two paths are respectively injected and locked into the 2 optical-frequency combs 302, so that the optical-frequency comb signals generated by the 2 optical-frequency combs 302 are coherent in phase, the frequency intervals of the optical signals generated by the 2 optical-frequency combs 302 are respectively FSR1 and FSR2, the signals generated by the 2 optical-frequency combs are respectively input into the 2 comb filters 303, the adjacent channel interval of the comb filters 303 is twice of the frequency interval of the optical-frequency combs 302, and therefore the frequency interval of the optical signals generated by the optical-frequency combs 302 is twice of the original optical-frequency comb after being filtered by the comb filters 303; the signal of the first optical comb 302 after passing through the comb filter 303 is input to the electro-optical modulator 304 in the transmission subsystem 10 as an optical carrier signal, and 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, wherein one path is used as reference light and input to the receiving subsystem 20, and the other path 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 second optical frequency comb 302 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, the other path is coupled with the modulated signal in the electro-optical modulator 304 in the transmitting subsystem 10 through the optical coupler 306 in the transmitting subsystem 10, and is 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 transmitting subsystem 10 select M channels of modulation signals and optical frequency comb signals, and after photoelectric conversion by M channels of detectors 309 in the transmitting subsystem 10, M channels of chirp microwave signals with orthogonal frequencies are obtained, and the M channels of orthogonal chirp signals are filtered and amplified to be radiated to a free space as transmitting signals of the radar transmitting subsystem 10.
As shown in fig. 5, the comb filter 303 is composed of a plurality of pass bands and stop bands periodically arranged at certain frequency intervals, and the comb filter 303 is used to filter the low repetition frequency optical frequency comb, so as to suppress some frequency spectrum components in the original optical frequency comb and allow the spectrum of a specific frequency to pass through, thereby realizing the conversion from the low repetition frequency optical frequency comb to the high repetition frequency optical frequency comb. The comb filter 303 performs spectrum filtering on the optical frequency comb 302, so that the repetition frequency of the optical frequency comb 302 signal is doubled, and the problem that the optical frequency comb signal with high repetition frequency is difficult to generate is solved.
The electro-optic modulator 304 operates at a minimum bias point to suppress 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. Receiving: echo signals are collected by N paths of receiving antennas, filtered and amplified by a receiving front end 311 and then respectively input to input ends of N electro-optical modulators 304 in a receiving subsystem 20, the N paths of echo signals are respectively modulated to optical carriers which are filtered by a second path of optical frequency comb 302 and then are branched, and then are respectively input to N arrayed waveguide gratings 308 in the receiving subsystem 20, each path of echo and a reference optical signal are divided into M paths of different channels to be output, and are input to a detector 309 in the receiving subsystem 20 to be subjected to deskew operation, M multiplied by N paths of deskew intermediate frequency signals are obtained, and digital signal processing is performed after analog-to-digital conversion, so that target information carried in the echo signals is obtained. M, N are positive integers, and the sum of M and N is more than 2. The deskew operation is to modulate a radar echo signal onto an optical carrier, and input the radar echo signal and reference light into the arrayed waveguide grating together, and the corresponding optical sidebands of the echo signal and the reference light signal are subjected to beat frequency processing in a photoelectric detector to obtain a difference frequency signal of the echo and the reference signal. The reference signal of the receiving end is not modulated by the echo signal, no new high-order modulation component is added to the reference signal, and finally the stray of the deskew intermediate-frequency signal in the receiver can be effectively inhibited.
The invention provides a microwave photon MIMO radar transmitting and receiving system. Generating two optical frequency comb signals with different repetition frequencies in a transmitter, wherein one optical frequency comb signal is used as a local oscillation optical frequency comb, the other optical frequency comb signal is used as an optical carrier and is modulated by a baseband linear frequency modulation signal, the modulated optical frequency comb is divided into two paths, one path and the local oscillation optical frequency comb beat frequency to obtain M paths of up-conversion radar transmitting waveforms, and the other path is transmitted to a receiving end to be used as a reference optical signal; n paths of receiving antennas at the receiving end receive the radar echo signals, then modulate the radar echo signals to an optical frequency comb coupled by the transmitting end, couple the radar echo signals with reference optical signals, and then input the radar echo signals to a photoelectric detector for beat frequency processing to obtain deskew intermediate frequency signals of the radar echo signals. And finally, obtaining M multiplied by N paths of digital signals after sampling by an analog-to-digital converter, and carrying out subsequent digital signal processing to obtain target information carried in radar echoes.
In a traditional MIMO radar receiving scheme, a radar echo signal directly modulates an optical reference signal, and the modulated signal is input to a detector for deskew reception to obtain an intermediate frequency signal (the reference optical signal is modulated once at a transmitting end and modulated again at a receiving end by the radar echo signal, so that an unnecessary high-order modulation component is easily generated). According to the radar echo signal receiving scheme provided by the scheme of the invention, the radar echo signal is modulated onto the optical carrier signal and then coupled with the reference optical signal to one path through the optical coupler, so that the reference optical signal is not subjected to secondary modulation, high-order modulation optical sidebands generated by multiple modulation are reduced, and thus, stray introduced by the high-order sidebands in the intermediate frequency signal is suppressed.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A microwave photonic MIMO radar transceiver system, comprising: a transmitting subsystem (10) and a receiving subsystem (20); generating two paths of optical frequency comb signals with different repetition frequencies in a transmitting subsystem (10), wherein one path of optical frequency comb signal is used as a local oscillator optical frequency comb signal, the other path of optical frequency comb signal is used as an optical carrier of the transmitting subsystem (10) and is modulated by a baseband linear frequency modulation signal, the modulated optical frequency comb signal is divided into two paths, one path of optical frequency comb signal and the local oscillator optical frequency comb signal are subjected to frequency beating to obtain M paths of up-conversion transmitting waveforms, and the other path of optical frequency comb signal is transmitted to a receiving subsystem (20) to be used as a reference optical signal; n paths of receiving antennas of the receiving subsystem (20) receive the echo signals, then modulate the echo signals to optical frequency comb signals coupled by the transmitting subsystem (10), couple the echo signals with reference optical signals, input the reference optical signals into a photoelectric detector to perform beat frequency processing to obtain MXN paths of deskew intermediate frequency signals of the echo signals, and perform digital signal processing after analog-to-digital conversion to obtain target information carried in the echo signals.
2. A microwave photonic MIMO radar transceiver system according to claim 1, wherein the transmit subsystem (10) comprises: a laser (301), 2 optical-frequency combs (302), 2 comb filters (303), 1 electro-optical modulator (304), 2 beam splitters (305), 1 optical coupler (306), 1 amplifier (307), 1 arrayed waveguide grating (308), M detectors (309), and a transmit front end (310); the output end of the laser (301) is respectively connected with the input ends of the 2 optical frequency combs (302), the output end of the 2 optical frequency combs (302) is respectively correspondingly connected with the input ends of the 2 comb filters (303), the output end of the first comb filter (303) is connected with the input end of the electro-optical modulator (304) of the transmitting subsystem (10), the output end of the electro-optical modulator (304) of the transmitting subsystem (10) is connected with the input end of the first beam splitter (305), the modulation wave input port of the electro-optical modulator (304) of the transmitting subsystem (10) inputs a baseband chirp signal, one output end of the first beam splitter (305) is connected with the first input end of the optical coupler (306) in the transmitting subsystem (10), the other output end of the first beam splitter (305) is connected with the receiving subsystem (20), the output end of the optical coupler (306) in the transmitting subsystem (10) is connected with the output end of the amplifier (307) in the transmitting subsystem (10) The input end of the amplifier (307) in the emission subsystem (10) is connected, the output end of the amplifier (307) in the emission subsystem (10) is connected with the input end of the arrayed waveguide grating (308) in the emission subsystem (10), M output ends of the arrayed waveguide grating (308) in the emission subsystem (10) are respectively connected with the input ends of M detectors (309) in the emission subsystem (10), and the output ends of the M detectors (309) in the emission subsystem (10) are connected with the emission front end (310); the output end of the second path comb filter (303) is connected with the input end of a second path beam splitter (305), one output end of the second path beam splitter (305) is connected with the second input end of an optical coupler (306) in the transmitting subsystem (10), and the other output end of the second path beam splitter (305) is connected with the receiving subsystem (20).
3. A microwave photonic MIMO radar transceiver system according to claim 2, wherein said receiving subsystem (20) comprises: n electro-optical modulators (304), N optical couplers (306), 1 amplifier (307), N arrayed waveguide gratings (308), M N detectors (309), and a receive front end (311); the output ends of the amplifiers (307) in the receiving subsystem (20) are respectively connected with the input ends of the N electro-optical modulators (304) in the receiving subsystem (20), the second input ends of N optical couplers (306) in the receiving subsystem (20) are respectively connected with the output ends of N electro-optical modulators (304) in the receiving subsystem (20), the modulated wave input ports of the N electro-optical modulators (304) in the receiving subsystem (20) are correspondingly connected with N output ends of a 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 N arrayed waveguide gratings (308) in the receiving subsystem (20), m output ends of each arrayed waveguide grating (308) in the receiving subsystem (20) are respectively connected with input ends of M detectors (309) in the receiving subsystem (20); the other output end of the first path of the beam splitter (305) is respectively connected with the first input end of the N optical couplers (306) of the receiving subsystem (20). The other output terminal of the second path of said beam splitter (305) is connected to the input terminal of an amplifier (307) in the receiving subsystem (20).
4. A microwave photonic MIMO radar transceiver system according to claim 3, characterized in that the operation of the transmitting subsystem (10) is: the laser (301) generates continuous wave laser signals and is divided into two paths, the two paths are respectively injected and locked into 2 optical frequency combs (302), the phases of the optical frequency comb signals generated by the 2 optical frequency combs (302) are coherent, the frequency intervals of the optical signals generated by the 2 optical frequency combs (302) are FSR1 and FSR2 respectively, the signals generated by the 2 optical frequency combs are respectively input into the 2 comb filters (303), the adjacent channel interval of the comb filters (303) is twice of the frequency interval of the optical frequency combs (302), therefore, the frequency interval is twice of the original optical frequency comb after the optical signals generated by the optical frequency combs (302) are filtered by the comb filters (303); the signal of the first optical comb (302) after passing through the comb filter (303) is input to an electro-optical modulator (304) in the transmitting subsystem (10) as an optical carrier signal, and 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, wherein one path is used as reference light and input into a receiving subsystem (20), and the other path is input into one input port of an optical coupler (306) in a transmitting subsystem (10); an optical frequency comb signal generated by the second optical frequency comb (302) is filtered by the comb filter (303) and then is also divided into two paths, one path is used as an optical carrier signal and is input into the receiving subsystem (20), the other path is coupled with a modulated signal in the electro-optical modulator (304) in the transmitting subsystem (10) through the optical coupler (306) in the transmitting subsystem (10), and the other path is amplified by the amplifier (307) in the transmitting subsystem (10) and then is input into the arrayed waveguide grating (308) in the transmitting subsystem (10). M paths of modulation signals and optical frequency comb signals are selected from different channels of the arrayed waveguide grating (308) in the transmitting subsystem (10), M paths of linear frequency modulation microwave signals with orthogonal frequencies are obtained after photoelectric conversion of M paths of detectors (309) in the transmitting subsystem (10), and the M paths of orthogonal linear frequency modulation microwave signals are used as transmitting signals of the radar transmitting subsystem (10) to be radiated to a free space after being filtered and amplified.
5. The microwave photonic MIMO radar transceiver system according to claim 4, wherein the operation of the receiving subsystem (20) is: echo signals are collected by N paths of receiving antennas, filtered and amplified by a receiving front end (311) and then respectively input to input ends of N electro-optical modulators (304) in a receiving subsystem (20), the N paths of echo signals are respectively modulated onto optical carriers which are filtered and then split by a second path of optical frequency comb (302), and then are respectively input into N array waveguide gratings (308) in the receiving subsystem (20), each path of echo and reference optical signals are divided into M paths of different channels to be output, and are input into a detector (309) in the receiving subsystem (20) to be subjected to deskew operation, M multiplied by N paths of deskew intermediate frequency signals are obtained, digital signal processing is performed after analog-to-digital conversion, and target information carried in the echo signals is obtained. M, N are positive integers, and the sum of M and N is more than 2.
6. The microwave photonic MIMO radar transceiver system of claim 5, wherein the deskew operation modulates a radar echo signal onto an optical carrier and inputs the modulated signal and the reference light to the arrayed waveguide grating together, and the optical sidebands corresponding to the echo signal and the reference light signal are subjected to beat frequency processing in the photodetector to obtain a difference frequency signal between the echo signal and the reference signal.
7. The microwave photonic MIMO radar transceiver system according to claim 2, wherein the laser (301) is configured to generate a continuous wave laser signal as an injection reference light source for the optical frequency comb (302).
8. The microwave photonic MIMO radar transceiver system as claimed in claim 2, wherein the comb filter (303) comprises a plurality of pass bands and stop bands periodically arranged at certain frequency intervals, and the low repetition frequency optical frequency comb is filtered by the comb filter (303) to suppress specific frequency spectrum components in the original optical frequency comb and let the spectrum of specific frequencies pass, thereby realizing the conversion from the low repetition frequency optical frequency comb to the high repetition frequency optical frequency comb.
9. The microwave photonic MIMO radar transceiver system of claim 2, wherein the electro-optic modulator (304) operates at a minimum bias point to suppress the optical carrier signal and to retain only the modulated optical frequency comb signal of the positive and negative first order optical sidebands.
10. A microwave photonic MIMO radar transceiver system according to claim 4 wherein the chirp signal is generated by a digital frequency synthesizer.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115001595A (en) * | 2022-05-11 | 2022-09-02 | 上海交通大学 | Radar communication integrated device and method based on all-optical information processing |
| CN115514413A (en) * | 2022-07-22 | 2022-12-23 | 西安空间无线电技术研究所 | Multichannel millimeter wave communication system based on optical frequency comb |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115001595A (en) * | 2022-05-11 | 2022-09-02 | 上海交通大学 | Radar communication integrated device and method based on all-optical information processing |
| CN115001595B (en) * | 2022-05-11 | 2023-10-13 | 上海交通大学 | Radar communication integrated device and method based on all-optical information processing |
| CN115514413A (en) * | 2022-07-22 | 2022-12-23 | 西安空间无线电技术研究所 | Multichannel millimeter wave communication system based on optical frequency comb |
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