CN111077519B - Microwave photon radar implementation method and system - Google Patents

Abstract

The present invention provides a microwave photonic radar implementation method and system, including: a transmitting link, a transmitting antenna, a receiving link, a receiving antenna and a data processing and control module, wherein one end of the transmitting link is connected to the data The processing and control module is connected, and the other end is connected to the transmitting antenna for providing the required radar transmission signal; the transmitting antenna is connected to the transmitting link for transmitting radar signals; the receiving link , one end of which is connected to the data processing and control module, and the other end is connected to the receiving antenna for extracting target information from the received radar signal; the receiving antenna, which is connected to the receiving link, uses for receiving radar signals; the data processing and control module, which is connected with the transmitting link and the receiving link, is used to control the timing, communication and extraction of the target signal from the echo signal of the radar system.

Description

A method and system for realizing microwave photonic radar

technical field

The invention relates to the technical field of radar, and in particular, to a method and system for realizing microwave photonic radar.

Background technique

Radar has played an increasingly important role in military and civilian applications due to its unique all-weather, all-weather technical advantages. The rise of unmanned technology combined with the existing development features of stealth, hypersonic and other weapons has made the sky threat style more diverse, which forces radar equipment to need the ability to effectively detect multiple targets at the same time. In addition, real-time perception of the battlefield environment and remote sensing mapping also require high-resolution and multi-band fusion images, which put forward higher precision and multi-band work requirements for air and space platform radars. The above requirements put forward functional reconfiguration and high resolution requirements for radar implementation technology, that is, wide frequency band tuning and large bandwidth and tunable requirements. Due to the limitation of "electronic bottleneck", traditional radar is difficult to break through in frequency band tuning and bandwidth. In recent years, microwave photonic technology, which is the intersection of microwave technology and photonic technology, has developed rapidly. This technology has inherent advantages such as high frequency, ultra-wideband, and low phase noise. Its application in radar systems has always been a research hotspot. The realization of radar system, namely microwave photonic radar, has attracted the attention of many countries and research teams.

In order to solve this problem of microwave photonic radar, as early as 2014, the Italian research group has reported the world's first microwave photonic technology radar in "Nature" (F.Scotti,F.Laghezza,D.Onori,and A.Bogoni," Field trial of aphotonics-based dual-band fully coherent radar system inamaritime scenario,"Iet Radar Sonar Nav 11(3),420-425(2017).), and then successively upgraded the radar system to dual-band integrated detection radar, Dual-band fusion imaging radar, this series of radars achieves optical sampling and reception of echo signals generated by chirp waveforms based on the optical frequency comb output by the same mode-locked laser at both ends of the transceiver, demonstrating the excellent tuning capability and frequency band compatibility of microwave photonic radars. Since its bandwidth is limited by the optical frequency comb spacing, and there are still challenges in the realization of passive mode-locked lasers with large mode spacing, this method cannot achieve the generation of large-bandwidth signals, and its bandwidth is only in the order of 100 MHz, which cannot achieve higher Precision detection. After that, the Institute of Electronics, Chinese Academy of Sciences (R.Li,W.Li,M.Ding,Z.Wen,Y.Li,L.Zhou,S.Yu,T.Xing,B.Gao,Y.Luan,Y.Zhu, P.Guo,Y.Tian,and X.Liang,"Demonstration of a microwave photonic synthetic aperture radar based on photonic-assisted signal generation and stretch processing,"Opt.Express 25(13),14334-14340(2017).), Nanjing University of Aeronautics and Astronautics (F.Zhang,Q.Guo,Z.Wang,P.Zhou,G.Zhang,J.Sun,and S.Pan,"Photonics-based broadband radar for high-resolution and real-time inverse synthetic aperture imaging,"Opt.Express 25(14),16274-16281(2017).), Air Force Early Warning Academy (A.Wang,J.Wo,X.Luo,Y.Wang,W.Cong,P.Du,J. Zhang,B.Zhao,J.Zhang,Y.Zhu,J.Lan,and L.Yu,"Ka-band microwave photonic ultra-wideband imaging radar for capturing quantitative target information,"Opt.Express 26,20708-20717( 2018).), Tsinghua University (S.Peng,S.Li,X.Xue,X.Xiao,D.Wu,X.Zheng,and B.Zhou,"High-resolution W-band ISAR imaging system utilizing alogic- operation-based photonic digital-to-analog converter, "Opt.Express 26, 1978-1987(2018).) The related research group constructed microwave photonic radar systems based on optical frequency doubling and optical down-conversion based on single-frequency lasers, respectively. The basic structures are: use different optical up-conversion technologies in the transmitting branch to obtain high-frequency and large-bandwidth transmission signals, and use different optical down-conversion technologies at the receiving end to achieve broadband echo signals. valid reception. The Air Force Early Warning Academy used the microwave photonic ultra-wideband radar prototype to achieve high-resolution imaging of civil aviation passenger planes, UAVs, and Leifeng Pagoda, demonstrating the ultra-wideband advantages of microwave photonic radar. Nanjing University of Aeronautics and Astronautics then further proposed a chip-based microwave photonic imaging radar architecture, which uses dual optical modulation to realize signal generation based on optical quadrupling technology. In view of the aforementioned detection requirements, the system reported above still has two deficiencies: First, both optical up-conversion and down-conversion are realized by controlling the bias state of the Mach-Zendl modulator, and its state is accurately controlled for a long time. It is still a challenge, which leads to the drift of the system state, which affects the practical value of microwave photonic radar; the second is that the above system also doubles the center frequency while realizing the bandwidth frequency doubling, and the center frequency and bandwidth cannot be independently tunable. , the strong attenuation of the high-frequency signal by the atmosphere limits its detection range.

Through the above comparative analysis, the current microwave photonic radar system cannot achieve independent tunability of center frequency and bandwidth and continuous operation without state offset, and it is difficult to meet the requirements of high-precision and multi-functional reconfigurable detection.

SUMMARY OF THE INVENTION

A series of concepts in simplified form have been introduced in the Summary section, which are described in further detail in the Detailed Description section. The Summary of the Invention section of the present invention is not intended to attempt to limit the key features and essential technical features of the claimed technical solution, nor is it intended to attempt to determine the protection scope of the claimed technical solution.

In order to at least partially solve the above-mentioned technical problems, the present invention provides a method and system for realizing a microwave photonic radar system, in which the multi-stage phase modulation plus optical combined filtering method is used to realize the emission and transmission of radar signals with tunable carrier frequency and bandwidth. Receiving and phase modulation do not require state control, which makes the system stable and simple in structure. The integrated design of the system composed of independent devices can realize low-cost microwave photonic radar system chips.

A microwave photonic radar implementation system, characterized in that it includes:

transmit chain, transmit antenna, receive chain, receive antenna and data processing and control module, wherein,

One end of the transmitting link is connected with the data processing and control module, and the other end is connected with the transmitting antenna, so as to provide the required radar transmission signal;

the transmit antenna, connected to the transmit link, for transmitting radar signals;

One end of the receiving link is connected with the data processing and control module, and the other end is connected with the receiving antenna, for extracting target information from the received radar signal;

the receiving antenna, connected to the receiving link, for receiving radar signals;

The data processing and control module, which is connected with the transmitting link and the receiving link, is used for controlling the timing, communication and extraction of the target signal from the echo signal of the radar system.

Further, the transmission chain includes: the input interface of the laser is connected to the data processing and control module, the output interface of the laser is connected to the input interface of the first phase modulator, and the output of the first phase modulator is connected. The interface is connected with the input interface of the dual-band-pass optical filter, the output interface of the dual-band-pass optical filter is connected with the input interface of the second phase modulator, and the output interface of the second phase modulator is connected with the band-pass optical filter. The output interface of the bandpass optical filter is connected to the input interface of the 1×2 coupler, the output interface of the 1×2 coupler is divided into two, and the first interface of the 1×2 coupler One output interface is connected to the input interface of the first photodetector, the second output interface of the 1×2 coupler is connected to the input interface of the adjustable optical delay line of the receiving link, the first The output interface of the photodetector is connected with the input interface of the power amplifier, wherein the microwave signal source is connected to the first phase modulator and the second phase modulator and provides them with phase modulation signals; The transmit chain provides the source of the optical signal.

Further, the receiving link includes: the output interface of the low noise amplifier is connected with the input interface of the third phase modulator, the output interface of the third phase modulator is connected with the input interface of the optical filter, the optical filter The output interface of the device is connected with the input interface of the second photodetector, the output interface of the second photodetector is connected with the input interface of the intermediate frequency filter amplifier, and the output interface of the intermediate frequency filter amplifier is connected with the input interface of the analog-to-digital converter. The output interface of the analog-to-digital converter is connected to the data processing and control module, wherein the output interface of the dimmable delay line is connected to the third phase modulator.

Further, the data processing and control module is connected with the laser of the transmitting link, the data processing and control module is connected with the analog-to-digital converter of the receiving link, the data processing and control The module communicates with the microwave signal source, the dual-band-pass optical filter, the band-pass optical filter, the power amplifier and the low-noise amplifier in the receiving link through a signal transmission line , The optical filter, the intermediate frequency filter amplifier and the analog-to-digital converter are connected to control parameters and working states.

Further, the input interface of the transmitting antenna is connected to the power amplifier of the transmitting chain for transmitting radar signals, and the output interface of the receiving antenna is connected to the low-noise amplifier of the receiving chain for transmitting radar signals. for receiving radar signals.

Further, the microwave signal source is any one of a direct digital frequency synthesizer or an optically generated microwave source, an optoelectronic oscillator or an optoelectronic hybrid microwave source.

Further, the laser is a distributed feedback laser.

Further, the dual-band-pass optical filter, the band-pass optical filter and the optical filter are realized by 3 discrete fiber grating filters, or by a multi-input multi-output programmable optical filter, or by a combination of the above two .

Further, the optical fiber connections of the optical devices in the system are all polarization-maintaining fibers, and the optical devices are all polarization-maintaining optical devices.

Further, it includes that the laser of the transmission chain is controlled by the data processing and control module to emit continuous light as an optical signal, and the first phase modulator modulates the optical signal emitted by the laser, and modulates the optical signal. The obtained optical signal enters the dual-band-pass optical filter to extract the desired optical signal, and the extracted optical signal enters the second phase modulator for secondary modulation. The first phase modulator and the second phase modulator The modulation signal of the device is provided by the microwave signal source controlled by the data processing and control module, the optical signal after secondary modulation enters the bandpass optical filter to extract the required optical signal, and the extracted optical signal enters the 1 The ×2 coupler is divided into two paths, the first path enters the first photodetector and is converted into an electrical signal, and the converted electrical signal is amplified by the power amplifier and then enters the transmitting antenna to transmit the radar signal;

The receiving antenna receives the radar signal, the received radar signal enters the low-noise amplifier for amplification, the amplified radar signal can be delayed by its own adjustable optical delay line, and the delayed radar signal enters the first low-noise amplifier. The three-phase modulator performs modulation, and the modulation signal of the third phase modulator is provided by the second channel of the 1×2 coupler. The modulated radar signal enters the optical filter for extraction, and the extracted radar signal is extracted. The radar signal is output to the second photodetector for conversion, the converted signal is output to the intermediate frequency filter amplifier for amplification, the amplified signal is output to the analog-to-digital converter for conversion, and the converted signal is output to the data processing and control. module, the data processing and control module performs signal processing.

Compared with the prior art, the beneficial effects of the present invention are:

Based on microwave photonic technology, the invention constructs a microwave photonic radar system which can be independently tuned in center carrier frequency and bandwidth and can satisfy high-precision detection. The signal of the channel is modulated differently, which realizes the generation of the radar waveform of the transmitting link and the receiving and processing of the echo signal of the receiving link. The multi-stage phase modulator and the optical combination filtering method are used to realize the tunable radar of both carrier frequency and bandwidth. The signal and phase modulator do not need state control, which can make the system working state of the microwave photonic radar realization method stable, and the structure is simple. can run stably.

The invention proposes a method for realizing a microwave photonic radar system based on discrete devices, and describes its integrated and micro-assembled forms. The integrated chip and the micro-assembled micro-system are beneficial to reduce size, weight and power consumption.

Description of drawings

In order that the advantages of the present invention may be more readily understood, the present invention briefly described above will be described in more detail by reference to specific embodiments shown in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail.

1 is a schematic structural diagram of a method for implementing a microwave photonic radar according to an embodiment of the present invention;

2 is a schematic diagram of a spectrum of an optical signal emitted by a laser according to an embodiment of the present invention;

3 is a schematic diagram of a spectrum of an optical signal selected by a dual-bandpass optical filter according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a spectrum of an optical signal selected by a bandpass optical filter according to an embodiment of the present invention.

Detailed ways

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar promotions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementation disclosed below.

For a thorough understanding of the embodiments of the present invention, detailed structures will be presented in the following description. Obviously, the implementation of the embodiments of the present invention is not limited to the specific details familiar to those skilled in the art. The preferred embodiments of the present invention are described in detail below, however, the present invention may have other embodiments in addition to these detailed descriptions.

It will be understood that although the terms first, second, etc. may be used in one or more embodiments of this specification to describe various information, such information should not be limited by these terms. These terms are only used to distinguish the same type of information from each other. For example, a first could be termed a second, and similarly, a second could be termed a first, without departing from the scope of one or more embodiments of this specification. Depending on the context, the word "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determining."

In the present invention, a microwave photonic radar implementation method is provided, and the present invention also relates to a microwave photonic radar implementation system, which will be described in detail one by one in the following embodiments.

Referring to FIG. 1 , a method for implementing a microwave photonic radar provided by the present invention includes a transmitting chain, a transmitting antenna, a receiving chain, a receiving antenna, and a data processing and control module.

Wherein, the transmission chain includes a laser, a first phase modulator, a dual bandpass optical filter, a second phase modulator, a bandpass optical filter, a 1×2 coupler, a first photodetector and a power amplifier. Specifically, in the connection of the transmission chain, the laser is connected to the first phase modulator through the connection mode of the optical waveguide, the first phase modulator is connected to the dual bandpass optical filter through the connection mode of the optical waveguide, and the first phase modulator is connected to the dual bandpass optical filter through the connection mode of the optical waveguide. The modulation signal of the modulator is provided by a microwave signal source, the microwave signal source is connected to the first phase modulator through the connection mode of the radio frequency waveguide, the double-band-pass optical filter is connected to the second phase modulator through the connection mode of the optical waveguide, and the second phase modulator is connected through the connection mode of the optical waveguide. The phase modulator is connected to the bandpass optical filter through the connection of the optical waveguide, the second phase modulator is connected to the microwave signal source through the connection of the radio frequency waveguide, and the light modulated by the second phase modulator enters the bandpass optical filter The optical sideband pair is divided into two paths by a 1×2 optical coupler. The first path is connected to the first photodetector through the connection of the optical waveguide, and the second path is connected to the adjustable light of the receiving link through the connection of the optical waveguide. The input end of the delay line is connected, and the first photodetector is connected with the power amplifier through the connection mode of the optical waveguide.

In the embodiment of the present invention, a single-frequency laser is used as the light source of the entire radar implementation method in the transmission link, and the continuous optical signal output by the laser enters the first phase modulator and is modulated by the first phase modulator, wherein the first phase modulation The modulation signal of the modulator is provided by the microwave signal source, and the modulation signal provided by the microwave signal source to the first phase modulator is a low-frequency narrow-band signal, and the modulated optical signal passes through a dual-band-pass optical filter, which filters out the required The optical sideband pair of the stage, the optical sideband modulates the second phase modulator, the modulation signal of the second phase modulator is provided by the microwave signal source, and the signal provided by the microwave signal source to the second phase modulator is another single phase modulator. The modulated optical signal is filtered by a bandpass optical filter to filter out the second optical sideband pair. The second optical sideband pair is divided into two paths by a 1×2 coupler, of which the first path enters the first photodetector The second channel enters the adjustable optical delay line of the receiving link, and the optical sideband pair of the first channel is converted into the required radar transmission signal by the first photodetector using the beat frequency principle. It is sent to the power amplifier. From this implementation process, it can be seen that the carrier frequency of the generated signal is related to the center frequency of the radio signal used by the first phase modulator and the second phase modulator, and the final signal bandwidth multiplier is controlled by the filter parameters.

The transmitting antenna and the power amplifier are connected by means of a radio frequency waveguide, and the radar transmitting signal amplified by the power amplifier is transmitted through the transmitting antenna.

The output interface of the receiving antenna and the input interface of the low-noise amplifier are connected by means of a radio frequency waveguide, and the radar signal received by the receiving antenna enters the low-noise amplifier.

The receiving chain includes a low noise amplifier, an adjustable optical delay line, a third phase modulator, an optical filter, a second photodetector, an intermediate frequency filter amplifier, and an analog-to-digital converter; In the connection relationship, the output interface of the low noise amplifier is connected with the input interface of the third phase modulator through the connection mode of the optical waveguide, and the input interface of the adjustable optical delay line is connected with the output interface of the second channel of the 1×2 coupler. The output port of the adjustable optical delay line is connected with the input port of the third phase modulator; the output port of the third phase modulator is connected with the input port of the optical filter, and the output port of the optical filter is connected with the input port of the second photodetector. The input interface is connected, the output interface of the second photodetector and the input interface of the intermediate frequency filter amplifier are connected by the connection mode of radio frequency waveguide, and the output interface of the intermediate frequency filter amplifier and the input interface of the analog-to-digital converter are connected by the connection mode of radio frequency waveguide.

In the embodiment of the present invention, in the receiving link, the target echo signal is received by the receiving antenna, the target echo signal enters the low-noise amplifier, the signal amplified by the low-noise amplifier enters the third phase modulator, and the third phase modulates The modulated signal of the transmitter is the optical local oscillator signal by the second optical sideband pair of the 1×2 coupler of the transmitting chain, and the third phase modulator modulates the echo signal after the low noise amplifier. Before the signal modulation is performed by the device, the adjustable optical delay line can delay the optical local oscillator signal accordingly, and the signal modulated by the third phase modulator enters the optical filter for filtering, and then converts to intensity modulation after the phase modulation is completed. , the optical signal output by the optical filter is input to the second photodetector through the input end of the second photodetector, and the second photodetector performs the beat frequency to realize the optical mixing process, and converts it into an intermediate frequency electrical signal containing the target position and speed information. The intermediate frequency electrical signal enters the intermediate frequency filter amplifier, and after being amplified, enters the analog-to-digital converter.

Data processing and control module, wherein the laser of the transmitting link is connected with the data processing and control module, and the analog-to-digital converter in the receiving link is connected and transmitted with the data processing and control module through the output interface after sampling and quantization by the electric ADC; Processing and control module Microwave signal source, dual-band-pass optical filter, band-pass optical filter and power amplifier through signal transmission line and transmitting chain, and low-noise amplifier, optical filter, IF filter amplifier and analog-digital amplifier in receiving chain The converter is connected for parameter and working state control.

In the embodiment of the present invention, the data processing and control module mainly controls the timing and communication of the entire radar system through software and realizes the extraction of target information from the echo signal. The specific method is: after the radar system is turned on, first make the laser work , emit the required wavelength and power, set the center frequency and bandwidth of the low-frequency narrowband signal, the frequency of the single-frequency signal and the response spectrum of the optical filter required for the output of the microwave signal source according to the center frequency and bandwidth to be realized, and then according to The optical delay length is selected according to the approximate position of the target; according to the selection of the transmission chain, data processing is performed on the echo data after mixing and sampling, and the target information is extracted.

Specifically, the microwave signal source is a direct digital frequency synthesizer, an optically generated microwave source (photoelectric oscillator, etc.), or a photoelectric hybrid microwave source. Of course, this embodiment does not limit the specific type of the microwave signal source, and everything is subject to the actual application; the laser of the transmitting link is a distributed feedback laser, and the type of the laser is also not limited; Among the filters, the dual-band-pass optical filter, the band-pass optical filter and the optical filter can be realized by 3 discrete fiber grating filters, or by a multi-input multi-output programmable optical filter, or by a combination of the above two, The present invention does not limit the specific implementation of the optical filter, and everything is subject to the actual application; in particular, in order to ensure the effective operation of the system, an optical amplifier can be added to each node of the optical path to amplify the optical signal, especially the dual-band-pass optical filter An optical amplifier can be added after the filter, bandpass optical filter and optical filter to amplify the optical signal. This is not a necessary component of the present invention, and does not belong to the limitation of the present invention, but is only for better working effect. Whether it is added or not is subject to actual application. In the embodiment of the present invention, the optical fibers used for connecting the optical devices in the system are all polarization-maintaining fibers, and the optical devices are all polarization-maintaining optical devices; and, in order to adapt to different detection targets, the adjustable optical delay line may be composed of optical fibers and switches. The formed dimmable delay line can also be an integrated optical delay line. The present invention does not limit the structure of the adjustable light delay line, and everything is subject to practical application.

In order to facilitate the public's understanding, the technical solution of the present invention will be further described in detail below theoretically.

Please refer to Figure 2, the continuous optical signal output by the laser is:

where E _c and ω _c are the amplitude and angular frequency of the continuous optical signal, respectively.

The low frequency narrowband signal output by the microwave signal source can be expressed as:

_VL (t)= _VL sin(ω ₀ t+πkt ² )

Among them, _VL , ω ₀ , and k are the amplitude, carrier frequency and chirp rate of the low-frequency narrowband signal, respectively. Applying it to the first phase modulator, the optical signal output by the first phase modulator can be expressed as:

Where m _L =πV _L /V _π1 is the modulation index of the first phase modulator, V _π1 is the half-wave voltage of the first phase modulator, and J _n (·) is the first kind of n-order Bessel function.

Referring to Figure 3, the ±n-order chirped optical sidebands are selected by using a dual-band-pass optical filter, and the selected optical signal can be expressed as:

The above-mentioned optical signal is sent to the second phase modulator, and another single-frequency radio frequency signal V _S (t)=V _S sin(ω ₁ t) with an amplitude V _S and an angular frequency of ω ₁ is generated by a microwave signal source. Under modulation, the output optical signal of the second phase modulator can be expressed as:

Where m _S =πV _S /V _π2 is the modulation index of the second phase modulator, and V _π2 is the half-wave voltage of the second phase modulator.

Referring to Figure 4, using another bandpass optical filter to select the +1-order single-frequency optical sideband of the -n-order chirped optical sideband and the -1-order single-frequency optical sideband of the +n-order chirped optical sideband band as the output optical signal,

的第一光电探测器，经拍频后所产生的雷达信为：The optical signal is sent to the responsivity of

The radar signal generated by the first photodetector after the beat frequency is:

可看到所产生信号的载频与两次调制用射频信号中心频率相关，最终信号带宽倍频数由滤波器参数控制实现。

It can be seen that the carrier frequency of the generated signal is related to the center frequency of the radio frequency signal used for the two modulations, and the final signal bandwidth multiplier is controlled by the filter parameters.

Suppose the echo signal backscattered by the target is:

V _e (t)=V _e cos[2(nω ₀ -ω ₁ )(t-τ _e )+2nπk(t-τ _e ) ² ]

Wherein V _e is the target echo amplitude, τ _e is the target echo delay. The local oscillator optical signal input by the third phase modulator (the +1-order single-frequency optical sideband of the -n-order chirped optical sideband coupled from the transmitter and the -1-order single-frequency optical sideband of the +n-order chirped optical sideband) sidebands) are:

Among them, τ _o is the delay of the optical local oscillator signal by the adjustable optical delay line. Let t ₁ =t-τ _e ,

t ₂ =t-τ _o The optical signal output by the third phase modulator is:

where m _e =πV _e /V _π3 is the modulation index of the third phase modulator, and V _π3 is the half-wave voltage of the third phase modulator. Using an optical filter to select the +1-order single-frequency optical sideband of the +n-order chirped optical sideband and the +1-order single-frequency optical sideband of the +1-order single-frequency optical sideband of the -n-order chirped optical sideband from the above-mentioned optical signals Wave chirped light sidebands, and vice versa, whose output can be expressed as:

Input to the second photodetector for beat frequency, and take out the low frequency component through IF:

Substituting the expressions of t ₁ and t ₂ into the above formula can be simplified to:

At this time, the high-frequency broadband signal becomes a single-frequency signal with a frequency of 2nk(τ _e -τ _o ), and the frequency of the signal can be made lower by adjusting the delay τ _o , which is convenient for subsequent digital signal processing.

The multi-order chirped light sidebands output by the first phase modulator cannot overlap each other in spectrum. Taking the n-order chirped light sideband as an example, the constraint relationship should be:

Therefore, in order to prevent spectral aliasing, the relationship between the center frequency and the bandwidth of the low-frequency narrowband signal should be

The optical sidebands of the output of the bandpass optical filter cannot be aliased:

The above formula is the relationship between the frequency of the single-frequency signal and the center frequency of the low-frequency narrowband signal.

The foregoing is a schematic solution of a method for implementing a microwave photonic radar according to this embodiment. It should be noted that the technical solution of the radar implementation method system and the technical solution of the above-mentioned radar implementation method belong to the same concept.

Specifically, a microwave photonic radar implementation system, including the device integration or micro-assembly processing of the transmitting link and the receiving link of the microwave photonic radar implementation method. Among them, integration refers to the use of heterogeneous integration technology to perform single-chip integration or multi-chip heterogeneous integration of devices other than transmitting and receiving antennas and data processing and control modules. After integration, the chip is integrated with the transmitting antenna, receiving antenna and Data processing and control modules are connected; micro-assembly refers to the use of micro-assembly technology to micro-assemble discrete devices to make the system smaller. The present invention does not limit which processing method is specifically adopted to realize the system, and everything is subject to the specific application.

The foregoing describes specific embodiments of the present specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that in the embodiments and still achieve desirable results. Additionally, the processes depicted in the figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments of the present invention do not describe all the details in detail, nor do they limit the present invention to only the described specific embodiments. Obviously, many modifications and changes can be made according to the contents of the embodiments of the present invention. The embodiments selected and specifically described in the present invention are to better explain the principles and practical applications of the embodiments of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims (9)

1. A microwave photonic radar implementation system, comprising:

the radar transmitting device comprises a transmitting link, a transmitting antenna, a receiving link, a receiving antenna and a data processing and control module, wherein one end of the transmitting link is connected with the data processing and control module, the other end of the transmitting link is connected with the transmitting antenna and is used for providing a required radar transmitting signal, an optical signal source of the transmitting link is provided by a laser, a continuous optical signal output by the laser is,

wherein E _c 、ω _c Amplitude and angular frequency of the continuous optical signal respectively;

the transmission chain comprises: the input interface of the laser is connected with the data processing and control module, the output interface of the laser is connected with the input interface of the first phase modulator, the output interface of the first phase modulator is connected with the input interface of the double-band-pass optical filter, the output interface of the double-band-pass optical filter is connected with the input interface of the second phase modulator, the output interface of the second phase modulator is connected with the input interface of the band-pass optical filter, the output interface of the band-pass optical filter is connected with the input interface of the 1 x 2 coupler, the output interfaces of the 1 multiplied by 2 coupler are divided into two, the first output interface of the 1 multiplied by 2 coupler is connected with the input interface of the first photoelectric detector, the second output interface of the 1 × 2 coupler is connected with the input interface of the adjustable optical delay line of the receiving link, and the output interface of the first photoelectric detector is connected with the input interface of the power amplifier;

the transmitting antenna is connected with the transmitting link and used for transmitting radar signals;

one end of the receiving link is connected with the data processing and control module, and the other end of the receiving link is connected with the receiving antenna and used for extracting target information from the received radar signals;

the receiving antenna is connected with the receiving chain and used for receiving radar signals;

the data processing and control module is connected with the transmitting link, the receiving link and the microwave signal source, and is used for controlling the radar to realize the time sequence and communication of the system and the extraction of target signals in echo signals, and simultaneously controlling the microwave signal source to send phase modulation signals to the first phase modulator and the second phase modulator, wherein low-frequency narrow-band signals output by the microwave signal source are represented as,

V _L (t)＝V _L sin(ω ₀ t+πkt ² )

wherein V _L 、ω ₀ And k are respectively the amplitude, carrier frequency and chirp rate of the low-frequency narrowband signal; applied to the first phase modulator, the optical signal output by the first phase modulator is represented as:

wherein m is _L ＝πV _L /V _π1 Is the modulation index, V, of the first phase modulator _π1 Is the half-wave voltage of the first phase modulator, J _n (. cndot.) is a first class of nth order Bessel function;

in the system, the carrier frequency and the bandwidth can be tuned independently by utilizing a multi-stage phase modulation and light combined filtering mode.

2. The microwave photonic radar implementation system of claim 1, wherein the receive chain comprises: an output interface of the low-noise amplifier is connected with an input interface of a third phase modulator, an output interface of the third phase modulator is connected with an input interface of an optical filter, an output interface of the optical filter is connected with an input interface of a second photoelectric detector, an output interface of the second photoelectric detector is connected with an input interface of an intermediate frequency filter amplifier, an output interface of the intermediate frequency filter amplifier is connected with an input interface of an analog-to-digital converter, an output interface of the analog-to-digital converter is connected with the data processing and control module, and an output interface of the adjustable light delay line is connected with the third phase modulator.

3. The microwave photonic radar implementation system of claim 2, wherein the data processing and control module is connected to the laser of the transmit chain, the data processing and control module is connected to the analog-to-digital converter of the receive chain, and the data processing and control module is connected to the transmit chain, the dual bandpass optical filter, the power amplifier, and the low noise amplifier, the optical filter, the intermediate frequency filter amplifier, and the analog-to-digital converter in the receive chain through signal transmission lines for parameter and operating state control.

4. The microwave photonic radar implementation system of claim 2, wherein an input interface of the transmitting antenna is connected to the power amplifier of the transmitting link for transmitting radar signals, and an output interface of the receiving antenna is connected to the low noise amplifier of the receiving link for receiving radar signals.

5. The microwave photonic radar implementation system of claim 1, wherein the microwave signal source is any one of a direct digital frequency synthesizer or a photo-generated microwave source, a photo-electric oscillator or a photo-electric hybrid microwave source.

6. The microwave photonic radar implementation system of claim 2, wherein the laser is a distributed feedback laser.

7. The microwave photonic radar implementation system of claim 2, wherein the dual bandpass optical filter, bandpass optical filter and optical filter are implemented by 3 discrete fiber grating filters, or by one multiple-in multiple-out programmable optical filter, or by a combination of the two.

8. The microwave photonic radar implementation system of claim 2, wherein the optical fiber connections of the optical devices in the system are all polarization maintaining optical fibers, and the optical devices are all polarization maintaining optical devices.

9. A microwave photon radar implementation method, which adopts the implementation system of any one of claims 1 to 8, and comprises,

the laser of the transmission link is controlled by the data processing and control module to transmit continuous light as an optical signal, the first phase modulator modulates the optical signal emitted by the laser, the modulated optical signal enters the dual-band-pass optical filter to extract the required optical signal, the extracted optical signal enters the second phase modulator to be modulated for the second time, the modulation signals of the first phase modulator and the second phase modulator are directly provided by the microwave signal source controlled by the data processing and control module according to the central frequency and the broadband to be realized, the optical signals after secondary modulation enter the band-pass optical filter to extract the required optical signals, the optical signals after extraction enter the 1 x 2 coupler to be divided into two paths, the first path enters the first photoelectric detector to be converted into electric signals, and the electric signals after conversion enter the transmitting antenna to be subjected to radar signal transmission after being amplified by the power amplifier;

the receiving antenna receives radar signals, the received radar signals enter a low-noise amplifier for amplification, the amplified radar signals can be delayed by the adjustable light delay line, the delayed radar signals enter a third phase modulator for modulation, modulation signals of the third phase modulator are provided by a second path of the 1 x 2 coupler, the modulated radar signals enter the optical filter for extraction, the extracted radar signals are output to a second photoelectric detector for conversion, the converted signals are output to an intermediate frequency filter amplifier for amplification, the amplified signals are output to an analog-to-digital converter for conversion, the converted signals are output to the data processing and control module, and the data processing and control module processes the signals.

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