1. A microwave photon broadband MIMO radar detection method of a step frequency modulation system is characterized in that,

at the transmitting end, a continuous wave optical signal with n wavelength components is divided into two paths, and the first path is modulated into a signal with a period and a pulse width of T respectively_prAnd T_pwThe optical pulse is subjected to cyclic frequency shift, and frequency shift delta f is respectively introduced into each wavelength component in the second path_iThen, i is 1, 2, …, n, with the frequency modulation slope, period and pulse width being γ and T respectively_crAnd T_cwThe linear frequency modulation microwave signal carries out single-sideband modulation on the optical signal, and the following conditions are met: t is_pr＝MT_cr＝MT_L≥N_maxT_LAnd T_L≥T_pw≥T_cw(ii) a Combining two optical signals into one path and then dividing the optical signal into two paths, wherein one path is used as an optical reference signal, the other path is subjected to wavelength division multiplexing into n paths of wavelength components, and the wavelength components are respectively subjected to photoelectric conversion into stepping frequency modulation microwave signals and then transmitted to a detection space; wherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma, and the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal;

at a receiving end, respectively modulating the optical reference signals by using target echoes collected by m receiving antennas, and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; processing the deskew signal to obtain target information; and m and n are positive integers greater than or equal to 2.

2. The method of claim 1, wherein the cyclic frequency shift is implemented by a frequency shift loop comprising a frequency shifter, an optical amplifier, and an optical multi-bandpass filter.

3. The method of claim 1, wherein the introducing a frequency shift Δ f separately for each wavelength component in the second path_iThe method is realized by the following steps: and demultiplexing the second path of optical signals to obtain n wavelength components, then respectively using a frequency shifter to shift the frequency of each wavelength component, and combining the n wavelength components after frequency shift into one path.

4. The method of claim 1, wherein the single sideband modulation is implemented by a cascaded intensity modulator and optical filter, or by a dual parallel intensity modulator.

5. The method of claim 1, wherein the target echoes collected by each receive antenna are modulated by an optical reference signal with a dual output intensity modulator operating at a quadrature bias point.

6. Stepping frequency modulation system microwave photon broadband MIMO radar detection device, its characterized in that includes:

the multi-wavelength continuous wave laser generation module is used for generating a continuous wave optical signal with n wavelength components and dividing the continuous wave optical signal into two paths;

a multi-wavelength cyclic frequency shift module for modulating the first continuous wave optical signal into a signal with a period and a pulse width of T respectively_prAnd T_pwPerforming cyclic frequency shift after the light pulse;

a multi-wavelength frequency shift module for introducing a frequency shift Δ f to each wavelength component in the second continuous wave optical signal_i，i＝1，2，…，n；

A single sideband modulation module for using the frequency modulation slope, the period and the pulse width of gamma and T respectively_crAnd T_cwThe linear frequency modulation microwave signal carries out single-sideband modulation on the optical signal output by the multi-wavelength frequency shift module;

T_pr＝MT_cr＝MT_L≥N_maxT_Land T_L≥T_pw≥T_cwWherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal, and the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma;

the photoelectric conversion module is used for demultiplexing one path of split signals of the combined signal of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module into n paths of wavelength components and respectively photoelectrically converting the split signals into stepping frequency modulation microwave signals;

the n transmitting antennas are used for transmitting the stepped frequency modulation microwave signals to a detection space;

m receiving antennas for receiving target echo signals;

the m microwave photon deskew receiving modules are used for modulating the other path of beam splitting signals of the combined signals of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module by using target echoes collected by the m receiving antennas respectively and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; both m and n are positive integers greater than or equal to 2;

and the signal processing module is used for processing the deskew signal to obtain target information.

7. The apparatus according to claim 6, wherein the multi-wavelength cyclic frequency shift module comprises an optical switch and a frequency shift loop consisting of a frequency shifter, an optical amplifier and an optical multi-passband filter.

8. The apparatus for detecting a stepped fm system microwave photonic broadband MIMO radar as claimed in claim 6, wherein the multi-wavelength frequency shift module comprises:

the first optical wavelength division multiplexer is used for dividing the second path of continuous wave optical signals into n wavelength components;

n frequency shifters for introducing a frequency shift Δ f to the n wavelength components respectively_i；

And the second optical wavelength division multiplexer is used for combining the n wavelength components after frequency shift into one path.

9. The apparatus according to claim 6, wherein the single-sideband modulation module is a cascade intensity modulator and an optical filter, or a dual-parallel intensity modulator.

10. The apparatus of claim 6, wherein the microwave photonic wideband MIMO radar detector comprises a dual output intensity modulator operating at a quadrature bias point for modulating the split signals with echo signals.

Background

The fluctuation of the scattering cross section of the target radar can cause the performance deterioration of the conventional single-transmitting single-receiving radar detection. By arranging a plurality of transmitting and receiving antennas at different positions and different angles, the multi-input multi-output (MIMO) radar can realize space diversity detection of a target, thereby improving the performances of reliability, precision and the like of detection. In addition, the current society has an urgent need for increasing the operating bandwidth of the MIMO radar, because the increase of the operating bandwidth not only can improve the resolution, but also can contribute to enhancing the detection accuracy of the target. However, the traditional MIMO radar using electronic technology has a small operation bandwidth, so its detection resolution is poor, and it is difficult to adapt to the requirements of high resolution such as automatic driving, target recognition, topographic mapping, etc. Therefore, the application of microwave photon Technology with characteristics of large bandwidth, small transmission loss, anti-electromagnetic interference, etc. to MIMO radar is expected to improve the detection performance (see [ Serafino G, Scotti F, Lembo L, et al. Forward a new generation of radio systems based on microwave Technology [ J ]. Journal of Lightwave Technology,2019,37(2): 643. 650 ]).

MIMO radar schemes implemented using microwave photonic technology have been reported (see [ Zhang F, Gao B, Pan S. Photonics-based MIMO radar with high-resolution and fast detection capability [ J ]. Optics Express,2018,26(13): 17529-. However, based on the current technical solution, the working bandwidth of the microwave photonic MIMO radar is still limited by the bandwidth of the electrical signal generator, so that the range detection resolution is difficult to be effectively improved. Therefore, the research on the microwave photon MIMO radar which can really break through the limitation of electronic bandwidth bottleneck has very important significance for improving the target detection capability.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a microwave photon broadband MIMO radar detection method of a step frequency modulation system, which has the capabilities of simultaneously generating a plurality of step frequency modulation microwave signals with ultra-large bandwidth and rapidly processing the step frequency modulation microwave signals and can realize real-time high-resolution detection.

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

a microwave photon broadband MIMO radar detection method of a step frequency modulation system,

at the transmitting end, a continuous wave optical signal with n wavelength components is divided into two paths, and the first path is modulated into a signal with a period and a pulse width of T respectively_prAnd T_pwThe optical pulse is subjected to cyclic frequency shift, and frequency shift delta f is respectively introduced into each wavelength component in the second path_iThen, i is 1, 2, …, n, with the frequency modulation slope, period and pulse width being γ and T respectively_crAnd T_cwThe linear frequency modulation microwave signal carries out single-sideband modulation on the optical signal, and the following conditions are met: t is_pr＝MT_cr＝MT_L≥N_maxT_LAnd T_L≥T_pw≥T_cw(ii) a Combining two optical signals into one path and then dividing the optical signal into two paths, wherein one path is used as an optical reference signal, the other path is subjected to wavelength division multiplexing into n paths of wavelength components, and the wavelength components are respectively subjected to photoelectric conversion into stepping frequency modulation microwave signals and then transmitted to a detection space; wherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma, and the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal;

at a receiving end, respectively modulating the optical reference signals by using target echoes collected by m receiving antennas, and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; processing the deskew signal to obtain target information; and m and n are positive integers greater than or equal to 2.

Preferably, the cyclic frequency shift is implemented by a frequency shift loop consisting of a frequency shifter, an optical amplifier and an optical multi-band-pass filter.

Preferably, the frequency shift Δ f is introduced separately for each wavelength component in the second path_iThe method is realized by the following steps: and demultiplexing the second path of optical signals to obtain n wavelength components, then respectively using a frequency shifter to shift the frequency of each wavelength component, and combining the n wavelength components after frequency shift into one path.

Preferably, the single sideband modulation is realized by a cascaded intensity modulator and optical filter, or by a dual parallel intensity modulator.

Preferably, the target echoes collected by the receiving antennas are modulated by an optical reference signal through a dual-output intensity modulator working at a quadrature bias point.

Based on the same inventive concept, the following technical scheme can be obtained:

stepping frequency modulation system microwave photon broadband MIMO radar detection device includes:

the multi-wavelength continuous wave laser generation module is used for generating a continuous wave optical signal with n wavelength components and dividing the continuous wave optical signal into two paths;

a multi-wavelength cyclic frequency shift module for modulating the first continuous wave optical signal into a signal with a period and a pulse width of T respectively_prAnd T_pwPerforming cyclic frequency shift after the light pulse;

a multi-wavelength frequency shift module for introducing a frequency shift Δ f to each wavelength component in the second continuous wave optical signal_i，i＝1，2，…，n；

A single sideband modulation module for using the frequency modulation slope, the period and the pulse width of gamma and T respectively_crAnd T_cwLinear frequency modulation ofThe microwave signal carries out single-sideband modulation on the optical signal output by the multi-wavelength frequency shift module; t is_pr＝MT_cr＝MT_L≥N_maxT_LAnd T_L≥T_pw≥T_cwWherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal, and the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma;

the photoelectric conversion module is used for demultiplexing one path of split signals of the combined signal of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module into n paths of wavelength components and respectively photoelectrically converting the split signals into stepping frequency modulation microwave signals;

the n transmitting antennas are used for transmitting the stepped frequency modulation microwave signals to a detection space;

m receiving antennas for receiving target echo signals;

the m microwave photon deskew receiving modules are used for modulating the other path of beam splitting signals of the combined signals of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module by using target echoes collected by the m receiving antennas respectively and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; both m and n are positive integers greater than or equal to 2; and the signal processing module is used for processing the deskew signal to obtain target information.

Preferably, the multi-wavelength cyclic frequency shift module comprises an optical switch and a frequency shift loop consisting of a frequency shifter, an optical amplifier and an optical multi-passband filter.

Preferably, the multi-wavelength frequency shift module includes:

the first optical wavelength division multiplexer is used for dividing the second path of continuous wave optical signals into n wavelength components;

n frequency shifters for introducing a frequency shift Δ f to the n wavelength components respectively_i；

And the second optical wavelength division multiplexer is used for combining the n wavelength components after frequency shift into one path.

Preferably, the single sideband modulation module is a cascade intensity modulator and an optical filter, or is a dual parallel intensity modulator.

Preferably, the microwave photon deskew receiving module comprises a dual-output intensity modulator operating at a quadrature bias point for modulating the split signals with echo signals.

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

1. the invention only uses one frequency shift loop to realize the cyclic frequency shift of the multi-wavelength optical signal, and only uses one linear frequency modulation microwave signal to drive the system, the system structure is relatively simple, and the system cost is greatly reduced;

2. the maximum total bandwidth of the step frequency modulation microwave signal generated by the invention can be N of the bandwidth of the linear frequency modulation microwave signal driving the system_maxAnd (4) doubling.

3. In the invention, only one double-output intensity modulator is used in each deskew receiving module to complete the electro-optical conversion of n stepping frequency modulation microwave signals, and the use of the photoelectric detector is balanced, so that the common-mode noise can be eliminated, and the signal-to-noise ratio of the deskew signals is improved.

4. The invention breaks through the limitation of the traditional method to the system bandwidth, can simultaneously generate and rapidly process a plurality of step frequency modulation microwave signals with ultra-large bandwidth, and simultaneously realizes ultra-high distance resolution and azimuth resolution.

Drawings

FIG. 1 is a schematic diagram of the structural principle of the radar detection device of the present invention;

FIG. 2 is a schematic structural diagram of a preferred embodiment of the radar detection apparatus of the present invention;

FIG. 3 is a schematic diagram of a frequency spectrum of an output optical signal of the frequency shift loop;

FIG. 4 is a schematic diagram of a frequency spectrum of an upper optical signal and a lower optical signal after coupling;

FIG. 5 is a schematic diagram illustrating a time correspondence between optical pulses and optical signals generated by a single sideband modulation module;

fig. 6 is a time-frequency diagram of the generation of stepped frequency modulated microwave signals.

Detailed Description

Aiming at the defects of the prior art, the solution idea of the invention is to fully combine the large bandwidth of the photon technology and the fine regulation and control advantages of the electronic technology, break through the bandwidth bottleneck of the traditional MIMO radar and realize rapid high-resolution detection.

The invention provides a microwave photon broadband MIMO radar detection method of a step frequency modulation system, which comprises the following steps:

at the transmitting end, a continuous wave optical signal with n wavelength components is divided into two paths, and the first path is modulated into a signal with a period and a pulse width of T respectively_prAnd T_pwThe optical pulse is subjected to cyclic frequency shift, and frequency shift delta f is respectively introduced into each wavelength component in the second path_iThen, i is 1, 2, …, n, with the frequency modulation slope, period and pulse width being γ and T respectively_crAnd T_cwThe linear frequency modulation microwave signal carries out single-sideband modulation on the optical signal, and the following conditions are met: t is_pr＝MT_cr＝MT_L≥N_maxT_LAnd T_L≥T_pw≥T_cw(ii) a Combining two optical signals into one path and then dividing the optical signal into two paths, wherein one path is used as an optical reference signal, the other path is subjected to wavelength division multiplexing into n paths of wavelength components, and the wavelength components are respectively subjected to photoelectric conversion into stepping frequency modulation microwave signals and then transmitted to a detection space; wherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma, and the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal;

at a receiving end, respectively modulating the optical reference signals by using target echoes collected by m receiving antennas, and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; processing the deskew signal to obtain target information; and m and n are positive integers greater than or equal to 2.

The technical scheme of the invention is explained in detail in the following with the accompanying drawings:

fig. 1 shows a basic structure of a radar detection device of the present invention, in which a broken line indicates an electrical path and a solid line indicates an optical path. As shown in fig. 1, the radar detection device of the present invention includes:

the multi-wavelength continuous wave laser generation module is used for generating a continuous wave optical signal with n wavelength components and dividing the continuous wave optical signal into two paths;

a multi-wavelength cyclic frequency shift module for modulating the first continuous wave optical signal into a signal with a period and a pulse width of T respectively_prAnd T_pwPerforming cyclic frequency shift after the light pulse;

a multi-wavelength frequency shift module for introducing a frequency shift Δ f to each wavelength component in the second continuous wave optical signal_i，i＝1，2，…，n；

A single sideband modulation module for using the frequency modulation slope, the period and the pulse width of gamma and T respectively_crAnd T_cwThe linear frequency modulation microwave signal carries out single-sideband modulation on the optical signal output by the multi-wavelength frequency shift module; t is_pr＝MT_cr＝MT_L≥N_maxT_LAnd T_L≥T_pw≥T_cwWherein M is a positive integer, N_maxIs the maximum number of cycles of the cyclic frequency shift, T_LFor the single cycle frequency shift delay of the cycle frequency shift, the corresponding frequency interval between every two of the n wavelength components is far larger than the bandwidth of the stepping frequency modulation microwave signal, and the difference value of the two introduced adjacent frequency shifts is larger than the product gamma tau of the target echo delay tau and the frequency modulation slope gamma;

the photoelectric conversion module is used for demultiplexing one path of split signals of the combined signal of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module into n paths of wavelength components and respectively photoelectrically converting the split signals into stepping frequency modulation microwave signals;

the n transmitting antennas are used for transmitting the stepped frequency modulation microwave signals to a detection space;

m receiving antennas for receiving target echo signals;

the m microwave photon deskew receiving modules are used for modulating the other path of beam splitting signals of the combined signals of the optical signals output by the multi-wavelength cyclic frequency shift module and the single-sideband modulation module by using target echoes collected by the m receiving antennas respectively and demultiplexing the modulated signals; respectively carrying out balanced photoelectric detection on optical signals with the same carrier frequency to obtain mxn deskew signals; both m and n are positive integers greater than or equal to 2; and the signal processing module is used for processing the deskew signal to obtain target information.

Each functional module in the above technical solution can be constructed by adopting various feasible existing technologies based on actual requirements.

Preferably, the multi-wavelength cyclic frequency shift module comprises an optical switch and a frequency shift loop consisting of a frequency shifter, an optical amplifier and an optical multi-passband filter.

Preferably, the multi-wavelength frequency shift module includes:

the first optical wavelength division multiplexer is used for dividing the second path of continuous wave optical signals into n wavelength components;

n frequency shifters for introducing a frequency shift Δ f to the n wavelength components respectively_i；

And the second optical wavelength division multiplexer is used for combining the n wavelength components after frequency shift into one path.

Preferably, the single sideband modulation module is a cascade intensity modulator and an optical filter, or is a dual parallel intensity modulator.

Preferably, the microwave photon deskew receiving module comprises a dual-output intensity modulator operating at a quadrature bias point for modulating the split signals with echo signals.

For the understanding of the public, the technical solution of the present invention is further described in detail by a specific embodiment as follows:

the specific structure of the radar detection device of this embodiment is shown in fig. 2, and the radar detection device is composed of a multi-wavelength continuous wave laser generation module (including a laser and an optical wavelength division multiplexer), a multi-wavelength cyclic frequency shift module (including an optical switch, a frequency shifter, an optical amplifier, and an optical multi-passband filter), a multi-wavelength frequency shift module (including an optical wavelength division multiplexer and a frequency shifter), a single-sideband modulation module (including an intensity modulator and an optical filter), a photoelectric conversion module (including an optical wavelength division multiplexer, a photoelectric detector, and an amplifier), a microwave photon deskew receiving module (including a dual-output intensity modulator, an optical wavelength division multiplexer, a balanced photoelectric detector, and an amplifier), a signal processing module, a transmitting antenna, and a receiving antenna. The chirp microwave signal in the single sideband modulation module of figure 2 is generated by an electrical signal generator.

First, n lasers of different wavelengths generate continuous wave optical signals (each having a wavelength λ)_iFrequency f_Li＝v/λ_iWherein i is 1, 2, …, n; v is the propagation speed of the optical signal) are combined into one path by an optical wavelength division multiplexer, wherein, the corresponding frequency interval between every two n wavelengths is f_Li+1-f_LiAnd should be much larger than the bandwidth of the stepped frequency modulated microwave signal generated by the system. The continuous wave optical signal is further divided into two paths, wherein the upper path optical signal is modulated into a period T by an optical switch_prPulse width of T_pwOf the light pulse of (2). The optical pulse is injected into a frequency shift loop formed by connecting a frequency shifter, an optical amplifier and an optical multi-passband filter end to end, wherein the optical amplifier is used for compensating the power loss of the loop so as to enable the open loop gain of the frequency shift loop to be 1, and the optical multi-passband filter is provided with n passbands corresponding to n wavelengths of the laser. Assuming that the frequency shift introduced by the frequency shifter is + Δ f, the bandwidth of each passband of the optical multi-passband filter is B_OBPFThe maximum number of times that the optical pulse circulates in the frequency shift loop is N_max＝[B_OBPF/Δf]+1 wherein [ x]Indicating a rounding down. It is also necessary to ensure that there is no residual optical pulse signal in the optical shift loop before the optical pulse enters the optical shift loop, i.e. that the trailing edge of the last optical pulse signal has left the optical shift loop before the leading edge of the optical pulse signal is injected into the optical shift loop. Therefore, T needs to be satisfied simultaneously_pr≥N_maxT_LAnd T_L≥T_pwWherein, T_LIndicating the delay of the optical pulse signal in the optical frequency shift loop. Thus, the light output by the frequency shift loopThe signal may be represented as:

wherein E is_PLWhich is indicative of the amplitude of the pulse signal,indicating the initial phase of the kth optical pulse signal. The spectrum of the optical signal output by the frequency shift loop is shown in FIG. 3, in which the dotted line is the frequency response of the multi-band-pass filter, frequency f_LiThe spectral lines at + (k +1) Δ f occur at different times, which are drawn at the same time for convenience.

The optical signal of the drop first passes through a first optical wavelength division multiplexer, thereby separating the optical signals of n wavelengths. Optical signals of each wavelength are respectively introduced with different frequency shifts deltaf through a frequency shifter_iAnd then the two are combined into one path by a second optical wavelength division multiplexer. The combined optical signal is sent to a single-sideband modulation module, the module can be realized by driving a double-parallel intensity modulator working in a carrier suppression single-sideband state by a narrow-band linear frequency modulation microwave signal generated by an electric signal generator, and can also be realized by a scheme that the linear frequency modulation signal drives the intensity modulator and then the intensity modulator is cascaded with an optical filter. Assuming that the center frequency and the chirp rate of the chirp microwave signal are respectively f_cAnd γ, the output signal of the carrier suppressed single sideband modulation (taking-1 order sideband as an example) module is:

wherein E is_CWIs the amplitude, T, of the optical signal_crAnd T_cwThe period and pulse width of the chirp microwave signal, respectively.

The optical pulse signals generated by the optical frequency shift loop and the optical signals generated by the carrier suppression single sideband modulation module are in one-to-one correspondence in time, as shown in a time-frequency diagram 5. Therefore, the upper and lower signals still need to satisfy the condition, T_pr＝MT_cr＝MT_LAnd T_pw≥T_cwWherein M is a positive integer. The optical signals of the upper path and the lower path are coupled into one path and then divided into two paths, the frequency spectrum is shown in fig. 4, wherein one path is further divided into m paths and is respectively sent to m microwave photon deskew receiving modules as optical reference signals. In addition, the other path of the microwave signal is sent to a photoelectric detector after passing through the wavelength division multiplexer, so that n stepping frequency modulation microwave signals can be generated, the time-frequency relationship of the stepping frequency modulation microwave signals is shown in fig. 6, and the expression is as follows:

wherein f is_ck＝f_c+(k+1)Δf-Δf_i。

The generated step frequency modulation microwave signals are amplified and then radiated to a detection space through a transmitting antenna, and m receiving antennas are used for collecting the reflected echoes of the target at the same time. In the microwave photon deskew receiving module, a target echo collected by a receiving antenna is amplified by an amplifier and then modulated by a dual-output modulator, wherein the dual-output modulator works at an orthogonal bias point. Two outputs of the dual-output modulator are divided into n paths through an optical wavelength division multiplexer respectively, and then optical signals with the same passband are sent to the balanced photoelectric detector, so that the target echo is subjected to deskew processing. There are m × n paths from n transmitting antennas to m receiving antennas, so that m × n deskew signals can be obtained. In order to avoid the influence of high frequency components on the deskew signal, the bandwidth of the balanced photoelectric detector is required to be smaller than f_Li-f_Li-1. Let the delays of m × n paths be τ, respectively_xWhere x is 1, 2, …, and m × n, the deskewed signal may be represented as:

the balanced photoelectric detector can eliminate common-mode noise and effectively improve the signal-to-noise ratio of the deskew signal. The obtained m × n deskew signals are sent to the signal processing module, and information of the target can be extracted, which is a mature technology in the prior art and is not described herein again for the sake of brevity.