阅读说明：本技术 基于光子采样的偏振复用微波光子雷达探测方法及系统 (Polarization multiplexing microwave photon radar detection method and system based on photon sampling ) 是由 郭清水 陈佳佳 于 2020-07-07 设计创作，主要内容包括：本发明公开了一种基于光子采样的偏振复用微波光子雷达探测方法和系统,探测方法为将光频梳信号分为两路,基带线性调频信号和目标回波信号分别对其中一路光频梳信号进行调制获得偏振态正交的发射调制光信号和接收调制光信号,将发射调制光信号和接收调制光信号合为一路偏振复用光信号后分为两路,两路分别检偏后获得发射调制光信号和包含发射调制光信号及接收调制光信号的复合光信号,将复合光信号进行光电转换及低通滤波后,即可得到中频信号,对中频信号进行处理,得到探测目标信息。本发明通过光子采样技术及光子偏振复用技术,实现宽带、频段可调雷达信号产生及接收,雷达系统紧凑简单,可一体化集成。(The invention discloses a polarization multiplexing microwave photon radar detection method and system based on photon sampling, wherein the detection method comprises the steps of dividing an optical frequency comb signal into two paths, respectively modulating one path of optical frequency comb signal by a baseband linear frequency modulation signal and a target echo signal to obtain a transmitting modulated optical signal and a receiving modulated optical signal with orthogonal polarization states, combining the transmitting modulated optical signal and the receiving modulated optical signal into one path of polarization multiplexing optical signal and then dividing the path of polarization multiplexing optical signal into two paths, respectively detecting the two paths to obtain the transmitting modulated optical signal and a composite optical signal containing the transmitting modulated optical signal and the receiving modulated optical signal, carrying out photoelectric conversion and low-pass filtering on the composite optical signal to obtain an intermediate frequency signal, and processing the intermediate frequency signal to obtain detection target information. According to the invention, through a photon sampling technology and a photon polarization multiplexing technology, the generation and the receiving of the radar signals with adjustable broadband and frequency band are realized, and the radar system is compact and simple and can be integrated integrally.)

1. A polarization multiplexing microwave photon radar detection method based on photon sampling is characterized by comprising the following steps:

the optical frequency comb signals are divided into two paths, and one path of optical frequency comb signals is modulated by the baseband linear frequency modulation signals to obtain first transmission modulation optical signals; the target echo signal modulates the other optical frequency comb signal to realize photon band-pass sampling and obtain a receiving modulated optical signal;

causing the receive modulated optical signal to be orthogonal to the polarization state of the first transmit modulated optical signal by polarization state control; combining a first transmitting modulation optical signal and a receiving modulation optical signal with orthogonal polarization states into a path of polarization multiplexing optical signal; sending the polarization multiplexing optical signal to a second analyzer for polarization detection, obtaining a composite optical signal containing a first transmitting modulation optical signal and a receiving modulation optical signal in the same polarization state, carrying out photoelectric conversion and low-pass filtering on the composite optical signal to obtain an intermediate frequency signal containing target information, and sampling and processing the intermediate frequency signal to obtain detection target information;

the target echo signal is subjected to photoelectric conversion and band-pass filtering by a first emission modulation optical signal or a second emission modulation optical signal to obtain an up-conversion radar emission signal; the radar emission signal is radiated to a space containing a target through an antenna and is obtained by reflection;

the second emission modulation optical signal is obtained by the polarization multiplexing optical signal through the first analyzer, and the polarization axis direction of the first analyzer is the same as the polarization state of the first emission modulation optical signal.

2. The method of claim 1, wherein the frequency spacing of the optical-frequency comb signalsf _LO Sum-band chirp signal frequencyf _LFM Satisfy the requirement off _LO > f _LFM 。

3. The method of claim 1, wherein the frequency of the upconverted radar-transmitted signal obtained by photoelectrically converting and bandpass filtering the first emission-modulated optical signal or the second emission-modulated optical signal isNf _LO + f _LFM Wherein, in the step (A),Nis a positive integer, by changingNThe operating band of the radar is changed.

4. The method as claimed in claim 1, wherein the specific method for modulating the other optical frequency comb signal by the target echo signal to realize the photonic band-pass sampling comprises: will have a frequency ofNf _LO + f _LFM Target echo signal pair frequency interval off _LO Based on the band-pass sampling principle, the frequency of the target echo signalnf _LO + f _LFM Is moved tof _LFM (ii) a The time domain representation of the optical frequency comb signal is periodic optical pulses.

5. The method of claim 1, wherein the optical-frequency comb signal is generated by a mode-locked laser, a femtosecond laser, an optical-frequency comb generator, an optical soliton technique, or a single-frequency signal externally-modulated electro-optic modulator.

6. A polarization multiplexed microwave photonic radar detection system based on photonic sampling, comprising:

an optical frequency comb generation module for generating two paths of frequency intervals off _LO Of (2) a lightA frequency comb signal;

the baseband modulation signal generation module is used for generating a baseband linear frequency modulation signal for modulating the optical frequency comb signal;

a polarization multiplexed electro-optic modulator for:

respectively modulating the baseband linear frequency modulation signal and the target echo signal on an optical frequency comb signal to obtain a first transmitting modulation optical signal and a receiving modulation optical signal;

causing the receive modulated optical signal to be orthogonal to the polarization state of the first transmit modulated optical signal by polarization state control;

combining a first transmitting modulation optical signal and a receiving modulation optical signal with orthogonal polarization states into a path of polarization multiplexing optical signal;

the optical amplifier is used for carrying out optical domain amplification on the polarization multiplexing optical signal;

the optical coupler is used for dividing the amplified polarization multiplexing optical signal into two paths which are respectively sent to the first analyzer and the second analyzer;

the first polarization analyzer is used for analyzing the polarization multiplexing optical signal to obtain a second emission modulation optical signal, and the polarization axis direction of the first polarization analyzer is the same as the polarization state of the first emission modulation optical signal;

the high-frequency photoelectric detector is used for converting the second emission modulation optical signal output by the first analyzer into an electric signal;

the band-pass filter is used for filtering out radar transmission signals of a required frequency band from the electric signals;

the receiving/transmitting antenna unit is used for transmitting radar transmitting signals, receiving target echo signals reflected by a target and simultaneously sending the target echo signals to the polarization multiplexing electro-optic modulator for modulation;

the second analyzer is used for analyzing the polarization multiplexing optical signal and obtaining a composite optical signal containing the transmitting modulation optical signal and the receiving modulation optical signal in the same polarization state;

the low-frequency photoelectric detector is used for performing photoelectric conversion on the composite light signal output by the second analyzer to obtain an intermediate-frequency signal carrying target information;

the low-pass filter is used for filtering other spurious signals in the intermediate frequency signal;

and the signal acquisition and processing module is used for performing analog-to-digital conversion on the intermediate frequency signals with other stray signals filtered out, performing radar digital signal processing and extracting target information.

7. The photon-sampling-based polarization multiplexed microwave photonic radar detection system of claim 6, wherein the optical-frequency comb generation module comprises a mode-locked laser, a femtosecond laser, an optical-frequency comb generator, or a single-frequency signal externally-modulated electro-optic modulator.

8. The photon-sampling-based polarization multiplexed microwave photonic radar detection system as in claim 6, wherein the frequency spacing of the optical frequency comb signalsf _LO Sum-band chirp signal frequencyf _LFM Satisfy the requirement off _LO > f _LFM 。

9. The photon sampling based polarization multiplexed microwave photonic radar detection system of claim 6, wherein the operating band of the radar is varied by varying the passband frequency of the bandpass filter.

10. The photonic-sampling-based polarization-multiplexed microwave photonic radar detection system of claim 6, wherein the polarization-multiplexed electro-optic modulator is a polarization-multiplexed mach-zehnder modulator, a polarization-multiplexed dual-parallel mach-zehnder modulator, or a polarization-multiplexed phase modulator.

Technical Field

The invention relates to a radar detection method, in particular to a microwave photon radar detection method and a microwave photon radar detection system adopting a photon sampling polarization multiplexing technology.

Background

With the development of emerging radar technology and the urgent need of novel situation awareness, the radar develops towards high-frequency, broadband, high-precision, real-time and multifunctional full-spectrum detection. This is required to cover different spectral spacesThe radar working wave band is flexible and adjustable, and signals can be processed and analyzed in real time. Limited by the bottleneck of the current electronic broadband signal generation and processing technology, when the microwave domain directly realizes the functions of signal generation, sampling, processing and the like, the frequency and bandwidth are low, the amplitude/phase response of the mixing link has nonlinear effect, and the amplification matching link is complex, so that the development of the radar to the high-frequency broadband is limited (see [ s. Kim, n. Myung, "Wideband linear frequency modulated wave compensation using system prediction and phase coefficients extraction method')"IEEE Microwave and Wireless Components Letters, vol. 17, no. 11, pp. 808-810,2007.]). Thanks to the rapid development of microwave photon technology, the optical domain generation, transmission and processing of microwave signals, such as photon mixing, photon sampling, photon true delay and the like, provide a new technical support for overcoming the electronic bottleneck problem of the traditional radar, improving the technical performance and becoming the key technology of the next generation of radar (see [ j. capmann, d. Novak, "microwave communications to world works"Nature photonics, vol. 1, no. 6, pp. 319-330,2007.]And [ J, McKinney, "Photonics of the future of radar"Nature,vol. 507, no. 7492, pp. 310-312, 2014.]). For example, band-pass sampling based on photonic technology can realize sampling of microwave signals by using narrow pulses with high repetition frequency, and related technologies have been used in novel radar reception technologies ([ p, Ghelfi, f, laghezza, f, Scotti, d, Onori, a, Bogoni, "Photonics for Radars Operating on multiple Coherent Bands,") "Journal of Lightwave Technology, vol. 34, no. 2,pp. 500-507, 2016.]) However, in the current receiving scheme based on photon band-pass sampling, the optical pulse repetition frequency is small, and the bandwidth of a receivable signal is limited; and the transmitting module and the receiving module are separated, so that the complexity of the whole system is increased, and the stability of the system is reduced. In addition, when the sampled signals are processed, a high-speed signal processor is still needed, so that the real-time performance of the whole system is limited.

The invention provides a new solution, photon direct sampling up-conversion of the transmitting signal and photon band-pass sampling down-conversion of the receiving signal can be realized based on a single integrated polarization multiplexing electro-optical modulator, and the intermediate frequency signal carrying target information is finally obtained based on the frequency-modulation removal technology of the optical domain, so that the frequency and bandwidth which are finally required to be sampled and processed are reduced. The radar system is compact and simple, the working wave band is flexible and adjustable, and signals can be processed quickly and in real time.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the defects of the prior art are overcome, based on the sampling principle, sampling up-conversion of radar transmitting signals and band-pass sampling down-conversion of receiving signals are realized by utilizing polarization multiplexing optical frequency comb signals, the wave band of the radar transmitting signals is flexible and adjustable, and the receiving signals can be subjected to photon band-pass sampling and deskew in real time. The system is compact and simple, and the working efficiency of the radar system is greatly improved.

The invention specifically adopts the following technical scheme to solve the technical problems:

a polarization multiplexing microwave photon radar detection method based on photon sampling specifically comprises the following steps:

the optical frequency comb signals are divided into two paths, and one path of optical frequency comb signals is modulated by the baseband linear frequency modulation signals to obtain first transmission modulation optical signals; the target echo signal modulates the other optical frequency comb signal to realize photon band-pass sampling and obtain a receiving modulated optical signal;

causing the receive modulated optical signal to be orthogonal to the polarization state of the first transmit modulated optical signal by polarization state control; combining a first transmitting modulation optical signal and a receiving modulation optical signal with orthogonal polarization states into a path of polarization multiplexing optical signal; sending the polarization multiplexing optical signal to a second analyzer for polarization detection, obtaining a composite optical signal containing a first transmitting modulation optical signal and a receiving modulation optical signal in the same polarization state, carrying out photoelectric conversion and low-pass filtering on the composite optical signal to obtain an intermediate frequency signal containing target information, and sampling and processing the intermediate frequency signal to obtain detection target information;

the target echo signal is subjected to photoelectric conversion and band-pass filtering by a first emission modulation optical signal or a second emission modulation optical signal to obtain an up-conversion radar emission signal; the radar emission signal is radiated to a space containing a target through an antenna and is obtained by reflection;

the second emission modulation optical signal is obtained by the polarization multiplexing optical signal through the first analyzer, and the polarization axis direction of the first analyzer is the same as the polarization state of the first emission modulation optical signal.

Based on the signal sampling principle, the first transmitting modulation optical signal and the second transmitting modulation optical signal have the same frequency spectrum distribution with the receiving modulation optical signal, and the instantaneous frequencies of the modulation signals in the same area in the frequency spectrum distribution are different by an intermediate frequency signal related to target information.

Preferably, the frequency interval of the optical frequency comb signalf _LO Sum-band chirp signal frequencyf _LFM Satisfy the requirement off _LO > f _LFM 。

Further, the frequency of the radar transmitting signal subjected to up-conversion obtained by the first transmitting modulation optical signal or the second transmitting modulation optical signal through photoelectric conversion and band-pass filtering isNf _LO + f _LFM Wherein, in the step (A),Nis a positive integer, by changingNThe operating band of the radar is changed.

Further, the target echo signal modulates the other optical frequency comb signal, and the specific method for realizing the photon band-pass sampling comprises the following steps: will have a frequency ofNf _LO + f _LFM Target echo signal pair frequency interval off _LO Based on the band-pass sampling principle, the frequency of the target echo signalnf _LO + f _LFM Is moved tof _LFM (ii) a The time domain representation of the optical frequency comb signal is periodic optical pulses.

Further, the optical frequency comb signal can be generated by a mode-locked laser, a femtosecond laser, an optical frequency comb generator, an optical soliton technology or a single-frequency signal external modulation electro-optical modulator, etc.

The following technical scheme can be obtained according to the same invention concept:

a photon sampling based polarization multiplexed microwave photonic radar detection system, comprising:

an optical frequency comb generation module for generating two paths of frequency intervals off _LO The optical frequency comb signal of (a);

the baseband modulation signal generation module is used for generating a baseband linear frequency modulation signal for modulating the optical frequency comb signal;

a polarization multiplexed electro-optic modulator for:

respectively modulating the baseband linear frequency modulation signal and the target echo signal on an optical frequency comb signal to obtain a first transmitting modulation optical signal and a receiving modulation optical signal;

causing the receive modulated optical signal to be orthogonal to the polarization state of the first transmit modulated optical signal by polarization state control;

combining a first transmitting modulation optical signal and a receiving modulation optical signal with orthogonal polarization states into a path of polarization multiplexing optical signal;

the optical amplifier is used for carrying out optical domain amplification on the polarization multiplexing optical signal;

the optical coupler is used for dividing the amplified polarization multiplexing optical signal into two paths which are respectively sent to the first analyzer and the second analyzer;

the first polarization analyzer is used for analyzing the polarization multiplexing optical signal to obtain a second emission modulation optical signal, and the polarization axis direction of the first polarization analyzer is the same as the polarization state of the first emission modulation optical signal;

the high-frequency photoelectric detector is used for converting the second emission modulation optical signal output by the first analyzer into an electric signal;

the band-pass filter is used for filtering out radar transmission signals of a required frequency band from the electric signals;

the receiving/transmitting antenna unit is used for transmitting radar transmitting signals, receiving target echo signals reflected by a target and simultaneously sending the target echo signals to the polarization multiplexing electro-optic modulator for modulation;

the second analyzer is used for analyzing the polarization multiplexing optical signal and obtaining a composite optical signal containing the transmitting modulation optical signal and the receiving modulation optical signal in the same polarization state;

the low-frequency photoelectric detector is used for performing photoelectric conversion on the composite light signal output by the second analyzer to obtain an intermediate-frequency signal carrying target information;

the low-pass filter is used for filtering other spurious signals in the intermediate frequency signal;

and the signal acquisition and processing module is used for performing analog-to-digital conversion on the intermediate frequency signals with other stray signals filtered out, performing radar digital signal processing and extracting target information.

Further, the optical frequency comb generating module can be a mode-locked laser, a femtosecond laser, an optical frequency comb generator or a single-frequency signal external modulation electro-optical modulator, etc.

Further, the frequency interval of the optical frequency comb signalf _LO Sum-band chirp signal frequencyf _LFM Satisfy the requirement off _LO > f _LFM 。

Further, the operating band of the radar is changed by changing the passband frequency of the bandpass filter.

Further, the polarization multiplexing electro-optical modulator is a polarization multiplexing Mach-Zehnder modulator, a polarization multiplexing double-parallel Mach-Zehnder modulator, a polarization multiplexing phase modulator, or the like.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1) the signal generating part of the invention realizes the up-conversion of the baseband modulation signal based on the optical frequency comb, and can flexibly change the working frequency band of the radar transmitting signal by adjusting the passband frequency of the band-pass filter.

2) The signal receiving part realizes photon band-pass sampling of high-frequency radar echo signals based on the same optical frequency comb (time domain signals are represented as optical pulses), and the coherence of radar receiving/signaling is ensured; meanwhile, based on the optical domain fusion of the transmitting modulation optical signal and the receiving modulation optical signal, the frequency modulation removing processing of the broadband linear frequency modulation signal can be realized.

3) The invention can realize up-conversion of baseband signals and band-pass sampling of received signals based on a single polarization multiplexing integrated modulator, and can realize flexible extraction of different optical signals through polarization state control; and the receiving modulation optical signal and the transmitting modulation optical signal have the same transmission path, so that unstable jitter of amplitude, phase and frequency of the frequency-modulated intermediate frequency signal caused by path difference is avoided.

Drawings

FIG. 1 is a schematic diagram of a microwave photonic radar system according to the present invention;

FIG. 2 is a schematic structural diagram of one embodiment of a microwave photonic radar system of the present invention;

FIG. 3 is a schematic diagram of the spectrum of signals generated at corresponding nodes in the microwave photonic radar system of FIG. 2, wherein:

fig. 3A is a schematic diagram of a spectrum of an optical frequency comb signal generated at a corresponding node a in fig. 2, fig. 3B is a schematic diagram of spectra of a first and a second transmission modulated optical signals generated at a corresponding node B in fig. 2, fig. 3C is a schematic diagram of a spectrum of an up-conversion chirp signal generated at a corresponding node C in fig. 2, fig. 3D is a schematic diagram of a spectrum of a reception modulated optical signal generated at a corresponding node D in fig. 2 after a polarization state is rotated, fig. 3E is a schematic diagram of a spectrum of a first transmission modulated optical signal and a spectrum of a reception modulated optical signal generated at a corresponding node E in fig. 2 and fig. 3F is a schematic diagram of a spectrum of a composite optical signal generated at a corresponding node F in fig. 2.

Detailed Description

Aiming at the defects of the prior art, the invention adopts the idea that a high-frequency-band tunable linear frequency modulation radar transmitting signal is generated based on a photon sampling up-conversion technology, the broadband echo signal is received by a photon band-pass sampling down-conversion and deskew method, the functions are simultaneously realized on a single integrated module by utilizing a polarization multiplexing technology, the system structure is simple and compact, the radar working parameters are flexible and adjustable, and the signal processing is real-time and efficient.

The polarization multiplexing microwave photon radar detection system based on photon sampling, disclosed by the invention, comprises an optical frequency comb generation module, a baseband modulation signal generation module, a polarization multiplexing electro-optical modulator, a first analyzer, a second analyzer and the like, as shown in fig. 1.

The optical frequency comb generation module generates a frequency interval off _LO The optical frequency comb signal is divided into at the input end of the polarization multiplexing electro-optical modulatorTwo paths; one path of optical frequency comb signal is a baseband linear frequency modulation signalf _LFM Modulating to obtain a first transmitting modulated optical signal, modulating the other path of optical frequency comb signal by a target echo signal to realize photon band-pass sampling, carrying out polarization deflection on the photon band-pass sampling to obtain a receiving modulated optical signal with a polarization state orthogonal to that of the first transmitting modulated optical signal, and dividing the receiving modulated optical signal and the first transmitting modulated optical signal into two paths after the receiving modulated optical signal and the first transmitting modulated optical signal are combined into one path of polarization multiplexing optical signal; one path of the light is analyzed by a first analyzer to obtain a second emission modulation light signal, wherein the direction of a polarization axis of the first analyzer is the same as the polarization state of the first emission modulation light signal, and the second modulation light signal is subjected to photoelectric conversion and band-pass filtering to obtain a light with a frequency ofNf _LO + f _LFM The up-conversion radar of (1) transmits a signal; the radar emission signal is radiated to a space containing a target through an antenna and reflected to obtain a target echo signal; and the other path of the signal is subjected to polarization detection by a second analyzer to obtain a composite optical signal containing the first transmitting modulation optical signal and the receiving modulation optical signal in the same polarization state, the composite optical signal is subjected to photoelectric conversion and low-pass filtering to obtain an intermediate frequency signal containing target information, and the intermediate frequency signal is sampled and processed to obtain detection target information.

In addition, a path of light can be directly separated from the first emission modulation optical signal and subjected to photoelectric conversion and band-pass filtering to obtain a signal with a frequency ofNf _LO + f _LFM The up-converted radar of (1) transmits a signal; the radar emission signal is radiated to a space containing a target through an antenna and is reflected, so that a target echo signal is obtained.

For the public understanding, the technical scheme of the invention is further explained in detail by a specific embodiment:

as shown in fig. 2, the microwave photon radar detection system of the present embodiment includes: 1 optical frequency comb produces the module, 1 baseband modulation signal, 1 polarization multiplex electro-optic modulator, 1 optical amplifier (EDFA), 1 optical coupler, 2 analyzer are first analyzer and second analyzer, 1 Low Frequency Photoelectric Detector (LFPD), 1 High Frequency Photoelectric Detector (HFPD), 1 Low Pass Filter (LPF), 1 Band Pass Filter (BPF), 1 electric power amplifier (EA), 1 Low Noise Amplifier (LNA), 1 transmitting antenna (Ta), 1 receiving antenna (Ra), 1 signal acquisition and processing module. And the second emission modulation optical signal generated by the first analyzer is used as the input of the high-frequency photoelectric detector, and is subjected to photoelectric conversion and band-pass filtering to obtain an up-conversion radar emission signal.

It should be noted that the optical frequency comb generating module may adopt various existing technologies, and preferably, the scheme of the single-frequency signal external modulation phase modulator is selected in this embodiment, and the optical frequency comb generating module is composed of a single-frequency local oscillator, a phase modulator and a laser. Single frequency local oscillator signalf _LO Modulating the carrier frequency by a phase modulator tof _C The continuous wave optical signal can obtain a frequency interval off _LO As shown in fig. 3A. Frequency spectrum of optical frequency comb signalf _Comb Can be expressed as:

f _Comb = f _C ± nf _LO (1)

whereinnIs a positive integer. The optical comb signal is fed to a polarization-multiplexed electro-optical modulator, and an integrated polarization-multiplexed mach-zehnder modulator, a polarization-multiplexed dual-parallel mach-zehnder modulator, a polarization-multiplexed phase modulator, or the like may be used for the polarization-multiplexed electro-optical modulator.

At the input end of the polarization multiplexing Mach-Zehnder modulator, the optical frequency comb signal is divided into two paths and is respectively sent to the input ends of the two sub Mach-Zehnder modulators. The optical frequency comb signal sent to the first mach-zehnder modulator (MZM 1) is modulated by the chirp baseband modulation signal, and positive and negative first-order modulation sidebands are generated with each frequency comb signal of the optical frequency comb as a carrier, respectively, to obtain a first transmission modulation optical signal, as shown in fig. 3B. Setting the instantaneous frequency of a chirp baseband modulated signalf _LFM (t) Comprises the following steps:

f _LFM (t)= f ₀ + kt(0≤ t ≤T) (2)

whereinf ₀Is the starting frequency of the chirp baseband signal,tas a matter of time, the time is,Tas a result of the period thereof,kis its chirp rate. At the moment, the first emission modulated light signal instantaneous frequencyf _{Comb_M} (t) Can be expressed as:

f _{Comb_M} (t) =f _C ±[nf _LO ±(f ₀ + kt)](0≤ t ≤T) (3)

similarly, the second emission modulated optical signal generated by the first analyzer is substantially the same as the first emission modulated optical signal, and the instantaneous frequency of the second emission modulated optical signal is also shown in equation (3). After the second emission modulated optical signal is sent to the high-frequency photoelectric detector to complete photoelectric conversion, the up-conversion chirp signal with the set working band can be filtered out through the band-pass filter, as shown in fig. 3C, the frequency of the signal isf _{LFM_T} (t) Can be expressed as:

f _{Comb_T} (t)= Nf _LO + f ₀ + kt(0≤ t ≤T) (4)

wherein, the frequency band of the signal can be changed by changing the pass band frequency of the band-pass filter, namely changing the size of N, the linear frequency-modulated signal after up-conversion is sent to the transmitting antenna after being amplified by the electric power amplifier, the signal is radiated to the space through the transmitting antenna and generates a target echo signal after encountering a detection target, the target echo signal is received by the receiving antenna and sent to the low-noise amplifier for amplification to obtain a radar receiving signal, when the target is a single-point target, the frequency of the receiving signalf _{LFM_R} (t) Can be expressed as:

f _{LFM_R} (t) =Nf _LO + f ₀ + k(t -τ) (0≤ t ≤T) (5)

whereinτIs the delay of the received signal relative to the transmitted signal. Modulating the optical frequency comb signal sent to a second Mach-Zehnder modulator (MZM 2) by using a radar receiving signal, generating positive and negative first-order modulation sidebands by using each frequency comb of the optical frequency comb as a carrier wave to obtain a receiving modulation optical signal, namely, carrying out band-pass sampling on the receiving signal of an optical domain, and receiving the frequency of the receiving modulation optical signalf _{Comb_MR} (t) Can be expressed as:

f _{Comb_MR} (t) =f _C ±[nf _LO ±(f ₀ + k(t -τ))](0≤ t ≤T) (6)

which has the same spectral distribution as the first and second emission modulated optical signals. The spectrum of the received modulated optical signal after changing the polarization state by the 90-degree polarization rotator is shown in fig. 3D. The receive modulated optical signal and the first transmit modulated optical signal are combined into a polarization multiplexed optical signal by a Polarization Beam Combiner (PBC) at an output end of the polarization multiplexing mach-zehnder modulator, where the polarization multiplexed optical signal includes the first transmit modulated optical signal and the receive modulated optical signal with orthogonal polarization states, as shown in fig. 3E. After the polarization multiplexing optical signal is sent to an erbium-doped fiber amplifier (EDFA) for amplification, the polarization multiplexing optical signal is divided into two paths through an optical coupler, one path is sent to a first analyzer, the polarization state of the analyzer is adjusted to enable the polarization axis of the analyzer to be the same as the polarization state of the first emission modulation optical signal, and then the output signal of the first analyzer only comprises the first emission modulation optical signal which is the second emission modulation optical signal sent to the high-frequency photoelectric detector as shown in fig. 3B and is the same as the output signal spectrum of the mach-zehnder modulator 1. And sending the other path of output signal of the optical coupler into a second analyzer, and adjusting the polarization state of the analyzer to ensure that the difference between the polarization axis of the analyzer and the polarization state of the first transmitting modulation optical signal is 45 degrees, and the difference between the polarization state of the analyzer and the polarization state of the receiving modulation optical signal is 45 degrees. The second analyzer outputs a composite optical signal comprising the first transmitted modulated optical signal and the received modulated optical signal, both modulated optical signals having the same polarization state, as shown in fig. 3F. Sending the output optical signal of the second analyzer to a low-frequency photoelectric detectorAfter completing photoelectric conversion and low-pass filtering with a low-pass filter, the intermediate frequency telecommunication system after frequency modulation removal can be obtainedkτAfter the intermediate frequency signal is subjected to analog-to-digital conversion, information such as target distance, speed, scattering characteristics and the like can be obtained based on a radar signal processing algorithm.

Finally, it should be noted that the above-mentioned list is only a specific embodiment of the present invention. The present invention is not limited to the above embodiments, and many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.