阅读说明：本技术 一种微波光子时分复用mimo雷达探测方法及系统 (Microwave photon time division multiplexing MIMO radar detection method and system ) 是由 郭清水 徐志伟 邓庆文 杨李杰 许桐恺 胡瑭 于 2020-06-03 设计创作，主要内容包括：本发明公开了一种微波光子时分复用MIMO雷达探测方法及实现该探测方法的系统,该方法在发射端,将基带线性调频信号调制到光载波上,通过光子倍频技术生成包含两个扫频分量的调制光信号；将该调制光信号分为两路,一路经光电转换后送入包含M个输出端的射频开关,射频开关的每路输出各连接一个发射天线,通过控制射频开关的通断时序实现M路阵列天线的时分探测信号发射；同时在接收端,将另一路调制光信号分为N路,分别对目标反射信号进行光域的下变频接收；在一个工作周期内得到M×N路携带目标信息的中频数字信号,对此数字信号进行处理,得到探测目标信息。本发明在具有高距离分辨率的同时,能够提高雷达系统的方位向角分辨率。(The invention discloses a microwave photon time division multiplexing MIMO radar detection method and a system for realizing the detection method, wherein at a transmitting end, a baseband linear frequency modulation signal is modulated onto an optical carrier, and a modulated optical signal containing two frequency sweeping components is generated by a photon frequency doubling technology; the modulation optical signal is divided into two paths, one path is sent into a radio frequency switch comprising M output ends after photoelectric conversion, each path of output of the radio frequency switch is respectively connected with a transmitting antenna, and the time division detection signal transmission of the M paths of array antennas is realized by controlling the on-off time sequence of the radio frequency switch; at the same time, at the receiving end, the other path of modulated optical signal is divided into N paths, and the down-conversion receiving of the optical domain is respectively carried out on the target reflection signal; and obtaining M multiplied by N paths of intermediate frequency digital signals carrying target information in a working period, and processing the digital signals to obtain detection target information. The invention can improve the azimuth angle resolution of the radar system while having high distance resolution.)

1. A microwave photon time division multiplexing MIMO radar detection method is characterized in that:

at a transmitting end, modulating a baseband linear frequency modulation signal onto an optical carrier, and obtaining a modulated optical signal containing two frequency sweeping components based on a microwave photon frequency doubling technology; dividing the modulated optical signal into two paths, wherein one path is subjected to photoelectric conversion and then is transmitted into an incident frequency switch; the radio frequency switch comprises M output ends, each output end is connected with one path of transmitting antenna unit, and the detection signals of the M paths of transmitting antenna units are sequentially transmitted into the space by controlling the switch time sequence of the radio frequency switch.

At a receiving end, N receiving antenna units receive target reflection signals, the target reflection signals are respectively sent to corresponding optical receiving units, meanwhile, the other path of modulation optical signals are divided into N paths and respectively sent to the N optical receiving units as reference optical signals, down-conversion of an optical domain of the target reflection signals is completed, and N paths of intermediate frequency signals are obtained. After the intermediate frequency signals are subjected to analog-to-digital conversion and digital domain data recombination, M multiplied by N paths of signals containing target information are obtained; and radar signal processing is carried out on the signal to obtain detection target information.

2. The method of claim 1, wherein the down-conversion in the optical domain is specifically: in a detection period, M target reflection signals sequentially received on each receiving antenna time sequence are sequentially modulated on one path of reference light signal, N paths of intermediate frequency signals are obtained after photoelectric conversion and low-pass filtering, and each path of intermediate frequency signal is M intermediate frequency signals carrying target information in time domain.

3. The method of claim 1, wherein the start time of the baseband FM signal and the channel ON time of the RF switch are synchronously controlled by the clock signal to ensure that the period of the baseband FM signal is equal to the duration of one working state of the RF switch.

4. The method of claim 1, wherein the antenna arrangement of the M transmit antenna elements and the N receive antenna elements may be a one-dimensional sparse array, a one-dimensional uniform array, a two-dimensional sparse array, a two-dimensional uniform array, or the like.

5. The method of claim 1, wherein the fine matching compensation of the relative delay of the N received signals is achieved by fine tuning the N-1 tunable optical delay lines with reference to the first optical receiving unit.

6. The utility model provides a microwave photon time division multiplexing MIMO radar detection system, includes transmitting terminal and receiving terminal, its characterized in that:

the transmitting end includes:

a laser source for generating a modulated optical carrier.

And the baseband frequency modulation signal source is used for generating a baseband frequency modulation signal required by photon frequency conversion.

And the photon frequency doubling module is used for modulating the baseband frequency modulation signal to an optical carrier to realize photon frequency doubling of the baseband frequency modulation signal.

And the high-frequency photoelectric detector is used for converting the modulated optical signal output by the photon frequency doubling module into an electric signal.

And the power amplifier is used for amplifying the power of the electric signal output by the high-frequency photoelectric detector.

The transmitting array antenna comprises M transmitting antenna units, and the transmitting antenna units are used for sequentially transmitting signals of the gating end of the 1 xM radio frequency switch.

And M output ports of the 1 xM radio frequency switch are respectively connected with the corresponding transmitting antenna units and are used for sequentially gating the transmitting antenna units and controlling the transmitting array antenna to sequentially work.

And the synchronization and control module is used for generating a base band frequency modulation signal, a 1 xM radio frequency switch and a time sequence synchronization and control signal of the signal acquisition and processing unit.

The receiving end includes:

the receiving array antenna comprises N receiving antenna units, and each receiving antenna unit is used for simultaneously receiving M echo signals reflected by a target in sequence.

And the 1 XN optical coupler is used for dividing the other path of modulated optical signal into N paths of reference optical signals.

And each optical receiving unit is used for respectively carrying out optical domain down-conversion processing on the echo signals received by the corresponding receiving antenna unit based on the reference optical signals to obtain intermediate frequency signals.

And the signal acquisition and processing unit is used for performing analog-to-digital conversion on the N paths of intermediate frequency signals, processing the radar digital signals and extracting target information.

7. The apparatus of claim 6, wherein the light receiving unit comprises:

and the optical delay line is used for carrying out delay compensation on the reference optical signal.

And the low-noise amplifier is used for carrying out low-noise amplification on the echo signals received by the receiving array antenna.

And the electro-optical modulator is used for modulating the echo signal after low-noise amplification to a reference optical signal to obtain a received optical signal.

And the low-frequency photoelectric detector is used for performing photoelectric conversion on the received optical signal to obtain a down-conversion intermediate-frequency signal.

And the low-pass filter is used for filtering high-frequency spurious frequency components in the down-conversion intermediate frequency signal.

8. The apparatus of claim 7, wherein the N-1 optical receiving units use the first optical receiving unit as a reference, and precisely adjust the corresponding tunable optical delay line to achieve precise matching compensation of the relative delay of the N received signals.

9. The apparatus as claimed in claim 6, wherein the synchronization & control module synchronously controls the start time of the baseband fm signal and the channel on time of the rf switch by the clock signal to ensure that the period of the baseband fm signal is equal to the duration of one operating state of the rf switch.

10. The device as claimed in claim 6, wherein the antenna arrangement of the transmitting array antenna and the receiving array antenna may be a one-dimensional sparse array, a one-dimensional uniform array, a two-dimensional sparse array, a two-dimensional uniform array, or the like.

Technical Field

The invention relates to a radar detection method, in particular to a time division Multiple-Input Multiple-Output (MIMO) radar detection method and system adopting a microwave photon auxiliary technology.

Background

The radar is widely applied to detection and identification of targets, and is an important basis for realizing the requirements in a multifunctional, high-precision and quick response mode. Requiring radar systems with wide operating bandwidths, large operating apertures, and fast signal processing speeds. Limited by the bandwidth limitation of electronic devices, the bandwidth directly generated by the broadband signal is only several gigahertz at present, the mixing and frequency multiplication of electronic domains introduce large amplitude jitter and phase distortion, and the amplification matching link is complex, which limits the development of radar to high-frequency broadband (see [ q.li, d.yang, x.mu, q.huo "," Design of the L-band wireless band LFM signal generator based on DDS and frequency multiplexing "," internal control Microwave Wave and Millimeter Wave Technology (ICMMT),2012 ]). In addition, Multiple Input Multiple Output (MIMO) Radar is widely used in Radar detection applications as a technology for effectively increasing the working aperture of Radar (see [ a. fricchen, j. hasch, c. waldschmidt, "a Cooperative MIMO Radar Network using high Integrated FMCW radars" IEEE Transactions on Microwave therapeutics and technologies, vol.65, No.4, pp.1355-1366,2017 ]). The same is limited by narrow-band response and high loss of the electronic link, which limits the application in the broadband detection scenario. Thanks to the rapid development of Microwave photon Technology and its characteristics of large bandwidth, low transmission loss, anti-electromagnetic interference, etc., it overcomes the electronic bottleneck problem of the conventional radar, improves the technical performance, and provides a new technical support, becoming the key Technology of the next generation of radar (see [ j.yao, "Microwave Photonics," Journal of Lightwave Technology, vol.27, No.3, pp.314-335,2009.] and [ f.zhang, q.guo, z.wang, p.zhou, g.zhang, j.sun, s.pan, "Photonics-based broadband and front-resolution and real-e inverting adaptation," optical express, vol.25, No.14, pp.16274-16281,2017 ]). A frequency division multiplexing MIMO radar based on microwave photonic technology has studied microwave photonic technology and the performance improvement of the radar system brought by MIMO technology in detail (see [ f.zhang, b.gao, and s.pan "," Photonics-based MIMO radar with high-resolution and fast detection capability "," Optics Express, vol.26, No.13, pp.17529-17540,2018 ]). However, frequency division multiplexing has limited frequency resources and the number of system channels, thereby limiting the equivalent aperture size of the system.

The invention provides a new solution, combines the microwave photon technology and the time division multiplexing MIMO technology, and greatly improves the frequency band utilization rate and the azimuth resolution of the radar system based on the advantages of the two technologies while ensuring the high distance resolution of the radar system.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art, provide a microwave photon time division multiplexing MIMO radar detection method, have the advantages of the microwave photon technology and the MIMO radar technology, and greatly improve the frequency band utilization rate and the azimuth angle resolution of a radar system.

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

a microwave photon time division multiplexing MIMO radar detection method is provided, wherein,

at a transmitting end, modulating a baseband linear frequency modulation signal onto an optical carrier, and obtaining a modulated optical signal containing two frequency sweeping components based on a microwave photon frequency doubling technology; dividing the modulated optical signal into two paths, wherein one path is subjected to photoelectric conversion and then is transmitted into an incident frequency switch; the M output ends of the radio frequency switch are respectively connected with a transmitting antenna unit, and the detection signals of the M paths of transmitting antenna units are sequentially transmitted into the space by controlling the switching time sequence of the radio frequency switch;

at a receiving end, receiving target reflection signals by N receiving array antennas, respectively sending the target reflection signals to corresponding optical receiving units, simultaneously dividing the other path of modulated optical signals into N paths, respectively sending the N paths of modulated optical signals to the N optical receiving units, and completing down-conversion of an optical domain of the target reflection signals to obtain N paths of intermediate frequency signals; after the intermediate frequency signals are subjected to analog-to-digital conversion and digital domain data recombination, M multiplied by N paths of signals containing target information are obtained; radar signal processing is carried out on the signal to obtain detection target information;

preferably, the down-conversion processing of the optical domain specifically includes: in a detection period, M target reflection signals sequentially received on each receiving antenna time sequence are sequentially modulated on one path of reference light signal, N paths of intermediate frequency signals are obtained after photoelectric conversion and low-pass filtering, and each path of intermediate frequency signal is M intermediate frequency signals carrying target information in time domain.

Preferably, the starting time of the baseband frequency modulation signal and the channel opening time of the radio frequency switch are synchronously controlled by a clock signal; and the period of the baseband frequency modulation signal is ensured to be equal to the duration of one working state of the radio frequency switch.

Preferably, the antenna arrangement modes of the M transmitting antenna units and the N receiving antenna units may be a one-dimensional sparse array, a one-dimensional uniform array, a two-dimensional sparse array, and a two-dimensional uniform array.

Preferably, the first light receiving unit is used as a reference, and N-1 adjustable light delay lines are accurately adjusted, so that the accurate matching compensation of the relative delay of N paths of received signals is realized.

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

a microwave photon time division multiplexing MIMO radar detection system comprises a transmitting end and a receiving end,

the transmitting end includes:

a laser source for generating a modulated optical carrier;

the base band frequency modulation signal source is used for generating a base band frequency modulation signal required by photon frequency conversion;

the photon frequency doubling module is used for modulating the baseband frequency modulation signal to an optical carrier to realize photon frequency doubling of the baseband frequency modulation signal;

the high-frequency photoelectric detector is used for converting the modulated optical signal output by the photon frequency doubling module into an electric signal;

the power amplifier is used for amplifying the power of the electric signal output by the high-frequency photoelectric detector;

the transmitting array antenna comprises M transmitting antenna units, and the transmitting antenna units are used for sequentially transmitting signals of the gating end of the 1 xM radio frequency switch; the 1 xM radio frequency switch is used for sequentially gating the transmitting antenna units and controlling the transmitting array antenna to sequentially work;

the synchronization and control module is used for generating a baseband frequency modulation signal, a 1 xM radio frequency switch and a synchronization time sequence and a control signal of the signal acquisition and processing unit;

the receiving end includes:

the receiving array antenna comprises N receiving antenna units, and each receiving antenna unit is used for simultaneously receiving M echo signals reflected by a target in sequence;

the 1 XN path optical coupler is used for dividing the other path of modulated optical signal into N paths of reference optical signals;

each optical receiving unit is used for respectively carrying out optical domain down-conversion processing on echo signals received by the corresponding N receiving antenna units based on the N paths of reference optical signals to obtain intermediate frequency signals;

the signal acquisition and processing unit is used for performing analog-to-digital conversion on the N paths of intermediate frequency signals, processing the radar digital signals and extracting target information;

preferably, the light receiving unit includes:

the optical delay line is used for carrying out delay compensation on the reference optical signal;

the low-noise amplifier is used for carrying out low-noise amplification on the echo signals received by the receiving array antenna;

the electro-optical modulator is used for modulating the echo signal after low-noise amplification to a reference optical signal to obtain a received optical signal;

the low-frequency photoelectric detector is used for performing photoelectric conversion on the received optical signal to obtain a down-conversion intermediate-frequency signal;

the low-pass filter is used for filtering high-frequency stray frequency components in the down-conversion intermediate-frequency signals;

furthermore, in a detection period, the electro-optical modulator sequentially modulates the M target reflection signals sequentially received by each receiving antenna time domain onto one path of reference optical signal, and obtains an intermediate frequency signal after photoelectric conversion and low-pass filtering.

Preferably, the starting time of the baseband frequency modulation signal and the channel opening time of the radio frequency switch are synchronously controlled by a clock signal; and the period of the baseband frequency modulation signal is ensured to be equal to the duration of one working state of the radio frequency switch.

Furthermore, the antenna arrangement mode of the transmitting array antenna and the receiving array antenna can be a one-dimensional sparse array, a one-dimensional uniform array, a two-dimensional sparse array and a two-dimensional uniform array.

Preferably, the N-1 optical receiving units use the first optical receiving unit as a reference, and precisely adjust the corresponding tunable optical delay line, so as to realize precise matching compensation of the relative delay of the N paths of received signals.

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

1) according to the invention, broadband signal generation is realized on the basis of a photon frequency doubling technology in a signal transmitting part, and broadband signal receiving is realized on the basis of a photon down-conversion technology in a receiving part, so that high-distance resolution radar detection can be realized; and the time division multiplexing of signals is realized through the radio frequency switch, and the complexity of the microwave photon MIMO radar system is reduced.

2) The invention adopts a time division multiplexing MIMO radar structure, which can improve the utilization rate of the system frequency band; and based on array arrangement and radar signal processing, data channels far more than the actual number of the transmitting and receiving array elements can be obtained, so that high radar azimuth angle resolution is realized.

3) The invention realizes signal transmission through the optical fiber, can meet the requirement of large-scale arrays on low transmission loss of signals, and can realize low dispersion and low amplitude jitter transmission of broadband signals; the delay accurate matching control among all channels can be ensured by finely adjusting the relative delay of the reference optical signal, and the system correction process is simplified.

Drawings

FIG. 1 is a schematic diagram of a MIMO radar system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a specific structure of an optical receiving unit in the MIMO radar system according to the present invention;

Detailed Description

Aiming at the defects of the prior art, the invention generates tunable linear frequency modulation signals with high frequency band based on the microwave photon frequency doubling technology, realizes broadband signal receiving through a microwave photon down-conversion method, realizes the orthogonality of transmitting signals by utilizing a time division multiplexing mode, is applied to a microwave photon MIMO radar system, improves the radar distance resolution and improves the azimuth angle resolution.

The invention relates to a microwave photon time division multiplexing MIMO radar detection system, which comprises a transmitting end and a receiving end as shown in figure 1.

At a transmitting end, modulating a baseband linear frequency modulation signal to an optical carrier output by a laser source through a photon frequency doubling module to generate a modulated optical signal containing two frequency sweeping components; dividing the modulated optical signal into two paths, wherein one path is converted into a frequency doubling linear frequency modulation signal by a photoelectric detector and then is transmitted into a frequency switch; the radio frequency switch comprises M output ends, each output end is connected with one path of transmitting antenna, and the transmitting array antenna sequentially transmits M detection signals to a space containing a target by controlling the switch time sequence of the radio frequency switch;

at a receiving end, dividing the other path of modulated optical signals into N paths and respectively sending the N paths of modulated optical signals to N optical receiving units, and respectively completing optical domain down-conversion of target reflected signals sequentially received by a receiving array antenna in the N optical receiving units to obtain N paths of intermediate frequency signals; after the intermediate frequency signals are subjected to analog-to-digital conversion and digital domain data recombination, M multiplied by N paths of signals containing target information are obtained; radar signal processing is carried out on the signal to obtain detection target information;

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

as shown in fig. 1, the radar detection system of the present embodiment includes: 1 laser source, 1 photon frequency doubling module, 1 baseband frequency modulation signal source, 1 synchronization & control module, 1 high-frequency photoelectric detector, 1 electric power amplifier (EA), 1 XM radio frequency switch, 1 transmitting array antenna (containing M antenna units), 1 receiving array antenna (containing N antenna units), N light receiving units, 1 XMN optical coupler, 1 erbium-doped fiber amplifier (EDFA), and 1 signal acquisition and processing unit.

It should be noted that the photon frequency doubling module and the light receiving unit may adopt various existing technologies, and preferably, the photon frequency doubling module is implemented by a mach-zehnder modulator feedback-controlled by a bias-actuating point controller. Preferably, as shown in fig. 2, the light receiving unit includes a Low Noise Amplifier (LNA), a light delay line, a mach-zehnder modulator (MZM), a Photodetector (PD), and a Low Pass Filter (LPF). The low-noise amplifier is used for performing low-noise amplification on a received signal, the Mach-Zehnder modulator is used for modulating the received signal by respectively using two frequency sweeping components in a reference optical signal as carriers, the photoelectric detector and the low-pass filter are sequentially used for performing photoelectric conversion and low-pass filtering on an output optical signal of the Mach-Zehnder modulator, and the optical delay line is used for compensating delay time difference among receiving channels.

The arrangement mode of the transmitting array antenna and the receiving array antenna can be a one-dimensional sparse array, a one-dimensional uniform array, a two-dimensional sparse array, a two-dimensional uniform array and the like, preferably the one-dimensional uniform array, wherein the distance between the antenna units of the receiving array antenna is lambda/2, the distance between the antenna units of the transmitting array antenna is Nlambda/2, N is the number of the antenna units of the receiving antenna array, and lambda is the radar center working wavelength.

The laser source generates a frequency f_LThe single-frequency optical signal enters an optical frequency doubling module, a baseband linear frequency modulation signal modulates an optical carrier at a Mach-Zehnder modulator, a modulated optical signal containing a positive and negative 2-order frequency sweeping signal is obtained at an output end, and the instantaneous frequency of the baseband frequency modulation signal is set as follows:

f_LFM(t)＝f₀+kt(0≤t≤T) (1)

wherein f is₀The initial frequency, T, and k are the cycle and the chirp rate of the baseband FM signal. The instantaneous frequency of the positive and negative 2-order swept sidebands of the modulated optical signal at this time can be expressed as:

the modulated optical signal is divided into two paths, one path is sent to a high-frequency photoelectric detector, and a 4-frequency-doubled linear frequency modulation signal can be obtained after photoelectric conversion, wherein the instantaneous frequency can be expressed as:

f_TR1(t)＝4f₀+4kt(0≤t≤T) (3)

the frequency-doubled linear frequency-modulated signal is amplified by an electric power amplifier and then sent to 1 multiplied by M radio frequency switches, a synchronization and control module sends out a synchronization control signal to control the radio frequency switches to be sequentially gated for work, and the duration from gating work to closing (gating work of adjacent ports) of one port is the period T of the linear frequency-modulated signal. Each output port of the radio frequency switch is connected to one antenna unit of the transmitting array antenna, and then the M antenna units radiate one time-width T chirp signal in sequence into the space, and the signals sequentially radiated by the antenna units in the transmitting array antenna can be represented as:

S_Tr,m(t)＝A_Tr,mexp{2π·[4f₀(t-(m-1)T)+2k(t-(m-1)T)²]}(0≤t≤MT,m＝1,2...M) (4)

S_Tr,mrepresenting the signal radiated by the mth antenna element; a represents the amplitude.

And the output end of the optical coupler is respectively connected with N optical receiving units, taking the first optical receiving unit as an example, assuming that the included angle between a connecting line of a point target at the far field of the antenna and the phase center of the antenna array and the normal line of the antenna array is theta, the signal radiated into the space is reflected after encountering a detection target, and the reflected signal is received and amplified by the receiving array antenna and is used as a driving signal to modulate the reference optical signal at the Mach-Zehnder modulator in the optical receiving unit. With respect to the transmitted signal, the received signal has a time delay τ, and the first path of received signal can be represented as:

S_Re,1,mrepresenting the mth echo signal received by the 1 st receive antenna element.

The reference optical signal comprises two frequency sweeping components, when the two frequency sweeping components in the reference optical signal are respectively used as carriers for modulation by a receiving signal, a negative 1-order sideband of a positive 2-order frequency sweeping signal of the reference optical signal is close to a negative 2-order sideband of the reference optical signal, and similarly, a positive 1-order sideband of a negative 2-order frequency sweeping signal of the reference optical signal is close to a positive 2-order sideband of the reference optical signal, the frequency difference between the frequency differences is 4k tau, and an output optical signal of the Mach-Zehnder modulator is sent to a low-frequency photoelectric detector to complete photoelectric conversion and low-pass filtering, so that an intermediate-frequency electrical signal after down-conversion can be obtained, and the frequency can be expressed:

S_1,m(t)＝A_1,mexp[2π(4kτt)]·exp[2(m-1)πNsinθ](0≤t≤T,m＝1,2...M) (6)

similarly, the other intermediate frequency electrical signals can be expressed as:

S_n,m(t)＝A_n,mexp[2π(4kτ_nt)]·exp[2(m-1)π(N+n-1)sinθ](0≤t≤T,m＝1,2...M,n＝1,2...N) (7)

S_n,mand the intermediate frequency electric signal is an intermediate frequency electric signal obtained by down-converting the mth echo signal received by the nth receiving antenna unit.

It should be noted that the front end of the mach-zehnder modulator of each light-receiving unit is connected with a high-precisionOptical delay lines for compensating the delay difference between the receiving channels to ensure tau_nEqual to τ.

Sampling the intermediate frequency signals of the N channels, and recombining digital domain data to obtain M multiplied by N paths of signals containing target information; the distance, azimuth angle, relative scattering intensity and other information of the target can be extracted from the signal through a MIMO radar correlation algorithm.

In addition, the synchronization and control module generates baseband frequency modulation signals, a 1 xM radio frequency switch, and a synchronization time sequence and control signal of the signal acquisition and processing unit; and synchronously controlling the starting time of the baseband frequency modulation signal and the channel opening time of the radio frequency switch so as to ensure that the period of the baseband frequency modulation signal is equal to the duration of one working state of the radio frequency switch.

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.