A microwave optical aperture conversion staring receiving system and method with optical domain squint correction

Abstract

The application discloses a microwave optical aperture conversion staring receiving system and method for optical domain desquamation, and belongs to the technical field of radar systems. The system comprises a local reference light generation module introduced on an existing digital beam forming radar receiver, which is used for generating a local optical reference signal by suppressing a single sideband modulation of another light signal output by a light source module. An optoelectronic detection and collection module is also introduced, which is used for collecting complete target echo light signals output by the optical Fourier transform module through an optoelectronic detector array. Meanwhile, the local optical reference signal and the target echo light signals achieve collinear space matching on a photosensitive surface of the optoelectronic detector array, and the two signals generate beat frequency. The square law detection characteristic of the optoelectronic detector is used to realize mixed frequency optical domain desquamation receiving of the target echo light signals. The target echo light signals received by the mixed frequency optical domain desquamation are used for simultaneously detecting the azimuth and distance of multiple targets.

Description

Technical Field

[0001] This invention belongs to the field of radar system technology, specifically relating to a method for optical domain deslant reception in microwave optical aperture transformation staring radar. Background Technology

[0002] Modern radar systems are evolving towards higher resolution, real-time multi-target monitoring, and miniaturized integration. To acquire high-precision range information and distinguish dense groups of targets, the bandwidth of radar transmission signals is increasing (reaching the GHz level). Simultaneously, to achieve transient detection of high-speed moving targets or saturation attacks within a large field of view, modern array radars must possess wide-field-of-view staring detection capabilities, simultaneously covering a vast airspace without mechanical scanning. The main existing technical solutions and operating principles addressing these detection requirements are as follows: Technical Solution 1: Phased array radar based on analog beamforming, its typical architecture is as follows: Figure 1 As shown, the core principle is to use the spatial interference of electromagnetic waves generated by multiple radiating elements in an antenna array for beam control. Specifically, each element or subarray at the antenna front end is independently equipped with an analog phase shifter and attenuator to adjust the phase and amplitude of the radio frequency signals in each channel. Through precise electronic control of each phase shifter, the electromagnetic waves radiated or received by the antenna array are superimposed in phase in a predetermined spatial direction, thus synthesizing a high-gain directional beam in space. In other directions, the electromagnetic waves cancel each other out of phase. The biggest advantage of this system is that it does not rely on mechanically rotating the antenna surface; it achieves rapid electronic scanning and flexible pointing of the beam in space simply by changing the control voltage or current applied to the phase shifters.

[0003] In technical solution 1, the traditional analog phased array uses radio frequency phase-shifting synthesis technology, which concentrates energy and information acquisition on a single or a few observation directions, essentially a serial airspace search system. Therefore, each sector within the radar's field of view can only be allocated dwell time sequentially, making it difficult to achieve multi-beam parallel large field of view instantaneous staring, and unable to complete the acquisition, track establishment, and tracking allocation of massive targets within an extremely short tactical window.

[0004] Technical Solution 2: Phased Array Radar Based on Digital Beamforming (DBF). DBF technology is currently the mainstream solution for achieving multi-beam staring detection, and its typical architecture is as follows: Figure 2As shown. Unlike analog phased arrays that synthesize a single beam at the radio frequency physical layer, a key feature of DBF technology is element-level digitization. In this architecture, each receiving element of the antenna array is connected to an independent down-conversion channel and a high-speed analog-to-digital converter (ADC). The spatial echo signal received by each antenna is independently sampled and converted into a digital signal, preserving the amplitude and phase information of the signal, and then uniformly transmitted to the back-end digital signal processing unit. In the digital domain, the system uses software algorithms to perform parallel complex multiplication and addition operations on massive amounts of multi-channel digital signals, i.e., digital phase and amplitude weighting, and then superimposes and synthesizes the beam. Since the beamforming process is transferred to the digital computing level, the same original echo data can be subjected to multiple different weighting calculations, thereby simultaneously forming multiple independent beams pointing in different directions within the same received pulse, realizing wide-field-of-view multi-target staring detection.

[0005] In technical solution 2, if the detection signal bandwidth reaches the GHz level, according to the Nyquist sampling theorem, the sampling rate of the ADC needs to be at least twice the signal bandwidth. In the DBF radar architecture, hundreds or thousands of array elements need to be equipped with high-speed ADCs. This not only leads to extremely high hardware costs, but also generates massive amounts of data at several gigabits per second, placing unbearable pressure on the backend signal transmission and real-time processing in terms of computing power and power consumption.

[0006] Technical Solution 3: Microwave Optical Aperture Transformation Imaging Radar. For example... Figure 3 As shown, its core principle is to achieve real-time extraction of echo signal azimuth information using two-dimensional spatial optical Fourier transform. In this system, the multi-channel broadband radio frequency echo signal received by the antenna array is input to the electro-optic modulator array, thereby mapping the radio frequency signal to the optical domain. Then, the modulated optical signal carrying radar echo information is transmitted through the fiber optic array, arranged on the front focal plane of the optical lens according to the topology corresponding to the radar antenna, and emitted into free space. The two-dimensional Fourier transform of the spatial signal is achieved through the optical lens. Therefore, the optical signal carrying electromagnetic wave echoes incident at different spatial angles is focused at different positions on the rear focal plane of the lens, forming corresponding light spots. This system uses passive optical lenses to replace the huge DBF computing network, directly achieving spatial angle separation in the optical domain, thus realizing real-time multi-beam detection with a large field of view.

[0007] In technical solution 3, the existing microwave optical aperture transformation staring radar effectively solves the problem of huge computing power and power consumption required for beamforming by using the spatial two-dimensional Fourier transform of the lens, and can realize large field of view multi-beam staring detection. However, this solution uses the phase information of the optical modulation sideband to realize the target orientation mapping and uses the CCD camera to read the coordinates of the light spot on the focal plane. It cannot obtain complete echo information, so it cannot realize the detection of target distance. Summary of the Invention

[0008] In view of the above, addressing the problem that existing microwave optical aperture transformation imaging radars cannot simultaneously detect the azimuth and range of multiple targets, this invention provides a microwave optical aperture transformation staring receiving system and method with optical domain deslant removal. It can achieve optical domain deslant removal processing of broadband signals through devices, reduce the bandwidth of target echo light signals, and on this basis, simultaneously achieve parallel detection of the azimuth and range of multiple targets.

[0009] To achieve the above-mentioned objectives, an embodiment provides a microwave optical aperture transformation staring receiver system for optical domain deslant removal, comprising a light source module, an array signal modulation module, and an optical Fourier transform module. The array signal modulation module modulates the radio frequency echo signals from each channel onto a beam of light output from the light source module to form an optical carrier signal, which is then transmitted into free space. The optical Fourier transform module collects target echo light signals with different angles of arrival from free space and performs a two-dimensional spatial Fourier transform. The system also includes a local oscillator reference light generation module and a photoelectric detection and acquisition module. The local oscillator reference light generation module is used to generate a local oscillator optical reference signal by modulating another beam of light output from the light source module with suppressed carrier single-sideband. The photoelectric detection and acquisition module includes a photoelectric detector array, which is used to acquire the complete target echo light signal output by the optical Fourier transform module through the photoelectric detector array. At the same time, the local oscillator optical reference signal and the target echo light signal achieve collinear spatial matching on the photosensitive surface of the photoelectric detector array. The two signals beat, and the square-law detection characteristic of the photoelectric detector is used to achieve the mixed optical domain deskewing reception of the target echo light signal. The target echo optical signal received by the mixed-frequency optical domain deslant receiver is used to simultaneously detect the azimuth and range of multiple targets.

[0010] Preferably, in the array signal modulation module, the modulated optical carrier signal is transmitted into free space through the fiber optic array. The transmitting end face of the fiber optic array adopts a non-periodic spiral fiber optic array based on the golden angle, and the first... n The polar coordinate position of the fiber ( ρ n , φ n Satisfies the mathematical relation: in, N For the number of array elements, R max This represents the maximum pole diameter of the spiral fiber array.

[0011] Preferably, in the optical Fourier transform module, a two-dimensional spatial Fourier transform is performed on the target echo light signal to achieve a scaled mapping of the target echo light signal, wherein the scaled mapping factor is...S scale for: in, λ o and λ RF These are the wavelengths of the light signal output by the light source module and the target echo light signal, respectively. D o and D RF These are the element spacings of the RF antenna array that receives RF echo signals from each channel and the fiber optic array that transmits modulated optical signals, respectively, in the array signal modulation module.

[0012] Preferably, the local oscillator reference light generation module includes a dual parallel Mach-Zehnder modulator and a radar transmission signal. The dual parallel Mach-Zehnder modulator, driven by the radar transmission signal, generates a local oscillator optical reference signal by suppressing single-sideband modulation of the input optical signal, ensuring that the local oscillator optical reference signal has only a +1 order sideband in the frequency domain, and its electric field intensity... E Lo ( t It can be approximated as: in, f 0 represents the optical signal frequency. f start The starting frequency of the linear frequency modulated signal. K The frequency modulation slope is t, and time is t. P 0 For optical signal power, This is an approximate symbol.

[0013] Preferably, in the photoelectric detection and acquisition module, the photosensitive surface size of the photodetector array element needs to be matched and designed according to the broadband diffusion amount corresponding to the maximum observation field of view of the radar and the maximum relative sweep bandwidth, so that the optical signal energy after broadband diffusion is received by the photosensitive surface of the detector array element as much as possible.

[0014] Preferably, in the photoelectric detection and acquisition module, the photocurrent signal corresponding to the target echo light signal received by the frequency mixing optical domain de-skewing receiver is... I IF ( t Approximately expressed as: in, φ 0 represents the inherent phase difference between the target echo optical signal and the local oscillator optical reference signal. The photocurrent signal retains the target echo time delay information, and its frequency... f IF Only KτIt is on the order of MHz. K For frequency modulation slope, τ Let t be the target echo delay, and t be time. This is an approximate symbol.

[0015] Preferably, the target echo optical signal received by the mixed optical domain deslant receiver is used to simultaneously detect the azimuth and range of multiple targets, including: For the azimuth angle, the spatial azimuth angle of the target is calculated by the different spot positions of the target echo light signal in the photodetector array; For distance, using the formula R = c·f IF / 2 K Extract the spatial distance of the target R ,in, f IF The frequency is calculated from the photocurrent signal corresponding to the target echo optical signal. c At the speed of light, K This represents the frequency modulation slope.

[0016] Preferably, the system further includes a wavefront repair module, which is used to extract a portion of the optical signal after transmission through the fiber array in the array signal modulation module, and to use it for closed-loop compensation of random phase delay errors caused by the fiber link.

[0017] To achieve the above-mentioned objectives, this invention also provides a microwave optical aperture transformation staring reception method for optical domain deslant correction, characterized in that the method employs the aforementioned system and includes the following steps: The local oscillator reference light generation module outputs another beam of light signal to the light source module, which is then modulated by suppressed carrier single-sideband to generate a local oscillator optical reference signal. The array signal modulation module modulates the radio frequency echo signals of each channel onto a beam of light output from the light source module to form an optical carrier signal, which is then emitted into free space. The optical Fourier transform module collects target echo light signals with different angles of arrival from free space and performs a two-dimensional spatial Fourier transform. The photodetector array included in the photoelectric detection and acquisition module acquires the complete target echo light signal output by the optical Fourier transform module. At the same time, the local oscillator optical reference signal and the target echo light signal achieve collinear spatial matching on the photosensitive surface of the photodetector array. The two signals beat, and the square-law detection characteristic of the photodetector is used to achieve the de-slant reception of the target echo light signal in the mixed optical domain. The target echo light signal received in the mixed optical domain is used to simultaneously detect the azimuth and range of multiple targets.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. This invention utilizes the two-dimensional spatial Fourier transform characteristics of parallel light speed of optical lenses to achieve multi-target azimuth detection. It also designs the photosensitive area of ​​the photodetector array to read the target echo light signal, so that the system can acquire the distance and angle information of multiple targets in a large field of view in real time without mechanical scanning or complex digital beamforming networks. Its ability to capture highly maneuverable targets far exceeds that of traditional analog phased array and digital phased array radars.

[0019] 2. This invention utilizes optical domain deskewing reception technology based on suppressed carrier single-sideband modulation in microwave optical aperture change staring radar. It employs coherent mixing and deskewing of the optical reference signal and echo signal directly on a photodetector, reducing the original GHz-level broadband RF echo to a narrowband MHz-level intermediate frequency signal in the optical domain. Furthermore, it shifts the complexity of broadband matched filtering from the digital domain to the optophysical layer. This eliminates the reliance on high-cost, high-power, high-speed ADC (analog-to-digital converter) arrays and DSP (digital signal processor) computing resources in the system backend. High-precision range calculation can be achieved using only conventional low-cost, low-speed ADCs, effectively saving hardware costs for large-array staring radar systems and alleviating data processing pressure when receiving multiple beams simultaneously. This makes the construction of large-scale array broadband staring radars engineering feasible. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a typical architecture for analog phased array radar receivers in the background technology; Figure 2 This is a typical architecture for digital beamforming radar receivers in the background technology; Figure 3 This is a typical architecture for microwave optical aperture transformation imaging radar in the background technology; Figure 4 This is a schematic diagram of the overall structure of the microwave optical aperture conversion staring receiving system with optical domain deslant provided in an embodiment of the present invention; Figure 5 This is a detailed structural schematic diagram of the microwave optical aperture conversion staring receiver system with optical domain deslant provided in an embodiment of the present invention; Figure 6 This is a flowchart of the microwave optical aperture transformation staring reception method for optical domain deslant provided in an embodiment of the present invention; Figure 7This is a two-dimensional light field intensity distribution diagram provided in an embodiment of the present invention; Figure 8 and Figure 9 These are the signals received by detectors (PD) 1 and 2 provided in this embodiment of the invention, where (a) is the time-domain waveform, (b) is the frequency, and (c) is the distance to the corresponding target. Among them, 1-laser, 2-optical amplifier, 3-1×N fiber optic splitter, 4-antenna array, 5-electro-optic modulator array, 6-optical phase control module, 7-optical antenna, 8-optical sideband and carrier separation module, 9-photodetector, 10-phase correction module, 11-optical lens, 12-beam splitter, 13-photodetector array, 14-1×2 fiber optic splitter, 15-dual parallel Mach-Zehnder modulator, 16-radar transmission signal, 17-analog-to-digital converter, 18-CCD camera. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0023] This invention provides a microwave optical aperture conversion staring receiver system with optical domain deslant. This system can achieve optical domain deslant processing of broadband signals: by using the local oscillator light and the reference linear frequency modulated signal with single-sideband suppressed carrier modulation, optical domain coherent heterodyne detection is completed at the PD array, realizing optical domain deslant reception of radar echo signals, reducing the GHz-level bandwidth radio frequency echo to a narrowband signal with a MHz-level frequency, and then using a low-cost, low-speed ADC to complete the acquisition of high-precision distance information. The system can also achieve parallel azimuth-range detection of multiple targets: it uses optical lenses to complete two-dimensional spatial Fourier transform to achieve azimuth detection of multiple targets with a large field of view, and uses a back-end photodetector array to extract waveform information after coherent reception to achieve parallel detection of range information of multiple targets, which effectively reduces the data rate of traditional digital beamforming computing networks in parallel azimuth-range detection of multiple targets.

[0024] like Figure 4 As shown in the embodiment, the microwave optical aperture transformation staring receiver system with optical domain deskewing includes a light source module, an array signal modulation module, an optical Fourier transform module, a local oscillator reference light generation module, a photoelectric detection and acquisition module, and a wavefront repair module.

[0025] In this embodiment, the light source module generates a light beam and transmits it to the array signal modulation module and the local oscillator reference light generation module. For example... Figure 5As shown, the light source module includes a laser 1, a 1×2 fiber optic splitter 14, and an optical amplifier 2. The laser 1 outputs a continuous beam and is split into two beams by the 1×2 fiber optic splitter 14. One beam is amplified by the optical amplifier 2 and then transmitted through the fiber optic transmission array signal modulation module, while the other beam is directly transmitted to the local oscillator reference light generation module.

[0026] In this embodiment, the local oscillator reference light generation module is used to generate a local oscillator optical reference signal by modulating another beam of light output from the light source module using suppressed carrier single-sideband modulation. For example... Figure 5 As shown, the local oscillator reference light generation module includes an optical carrier entering a dual parallel Mach-Zehnder modulator (DPMZM) 15 and a radar transmission signal 16. Another optical signal output from the light source module is input to the DPMZM 15 and driven by the radar transmission signal 16 (usually a broadband linear frequency modulated signal). By suppressing the carrier's single-sideband modulation, a local oscillator optical reference signal is generated, so that the local oscillator optical reference signal has only a +1 order sideband in the frequency domain, and its electric field intensity... E Lo ( t It can be approximated as: in, f 0 represents the optical signal frequency. f start The starting frequency of the linear frequency modulated signal. K The frequency modulation slope is t, and time is t. P 0 For optical signal power, The symbol is an approximation. The suppressed carrier single-sideband modulation method can effectively avoid image interference and spectral aliasing caused by ordinary double-sideband modulation.

[0027] In this embodiment, the array signal modulation module is used to modulate the radio frequency echo signals of each channel onto a beam of light output from the light source module and then transmit it into free space. For example... Figure 5 As shown, the array signal modulation module includes 1× N Fiber optic splitter 3, antenna array 4, electro-optic modulator array 5, and fiber optic array 7. A beam of light signal output from the light source module passes through a 1×... N After fiber optic splitter 3, it is divided into N Each branch input is fed into the electro-optic modulator array 5, thereby mapping the radio frequency microwave echo signals received by the antenna array 4 from each channel into the optical domain. The modulated optical carrier signal is then input to the fiber array 7, which is arranged on the end face and serves as an optical antenna, and transmitted into free space. To solve the problem of spatial grating lobes in broadband beamforming using traditional periodic arrays, the transmitting end face of this invention employs a non-periodic spiral fiber array based on a golden angle. The first branch input is on the array surface... n The polar coordinate position of the fiber ( ρn , φ n Satisfies the mathematical relation: in, N For the number of array elements, R max This represents the maximum pole diameter of the spiral fiber array.

[0028] In this embodiment, the wavefront repair module is used to extract a portion of the optical signal transmitted and emitted into free space by the fiber array 7, and to provide closed-loop compensation for random phase delay errors caused by factors such as ambient temperature and mechanical stress in the fiber optic link. Figure 5 As shown, the wavefront repair module includes an optical phase control module 6, a photodetector 9, and a phase correction module 10. Specifically, the optical sideband and carrier separation module 8 collects optical signals from free space and extracts the partially modulated optical carrier signals transmitted and emitted into free space by the fiber optic array. This extracted signal is then input into the photodetector 9 to extract the phase error information of each channel. The phase correction module 10 calculates the compensation voltage based on the extracted phase error information and feeds it back to the optical phase control module 6. This performs real-time pre-compensation on the phase of the modulated optical carrier signals of each channel, thereby ensuring that the optical wavefront mapped from the antenna array 7 to free space maintains phase coherence.

[0029] In this embodiment, the optical Fourier transform module utilizes a passive optical lens to perform spatial processing on the light field distribution carrying radar spatial echo information, achieving physical separation of multiple targets' spatial angles of arrival. Specifically, it collects target echo light signals with different angles of arrival from free space and performs a two-dimensional spatial Fourier transform. For example... Figure 5 As shown, the optical Fourier transform module includes an optical sideband and carrier separation module 8, a beam splitter 12, and an optical lens 11. After wavefront repair and modulation to carry the echo phase, the optical carrier signal is transmitted into free space by a non-periodic spirally arranged optical antenna. These spatially distributed optical signals are transmitted to the optical lens 11 after passing through the optical sideband and carrier separation module (retaining the +1st order optical sideband) 8 and the beam splitter 12. The beam undergoes a two-dimensional spatial Fourier transform as it passes through the optical lens 11. Broadband target echo information with different angles of arrival is then scaled down and focused onto the photodetector array 13. The scaling factor is... S scale for: in, λ o and λ RF These are the wavelengths of the light signal output by the light source module and the target echo light signal, respectively. D o and DRF These represent the element spacing between the RF antenna array 4, which receives RF echo signals from each channel, and the fiber optic array 7, which transmits modulated optical signals, respectively, in the array signal modulation module. The corresponding imaging point position coordinates ( x,y )for: in, f lens The focal length of the lens. θ x and θ y These are the azimuth and elevation angles of the radio frequency echo, respectively. In actual spectrum sensing processes, due to the microwave wavelength... λ RF Changes in instantaneous frequency can cause spatial stretching and dispersion of the light spot on the detector array plane.

[0030] In this embodiment, the photoelectric detection and acquisition module is used to complete the spatial beam combining of the target echo light signal and the local oscillator optical reference signal, coherent beat frequency detection, and low-speed digital acquisition. For example... Figure 5 As shown, the photoelectric detection and acquisition module includes a photodetector array 13 and an analog-to-digital converter (ADC) 17. After the target echo light signal undergoes a two-dimensional Fourier transform by the optical lens 12, light spots containing target information at different spatial orientations are incident on the corresponding pixel elements of the photodetector array 13. Simultaneously, the local oscillator optical reference signal, generated by the local oscillator reference light generation module and suppressed carrier single-sideband, is emitted in a divergent state and passes through the beam splitter 11, achieving spatial beam combining with the target echo light signal. Subsequently, after wavefront conversion by the optical lens 12, it is collimated into a parallel light field, uniformly illuminating the detection surface of the photodetector array 13 in the form of a plane wave, achieving collinear spatial matching with the radio frequency target echo light signal on the photosensitive surface of the detector. Finally, the target echo light signal is focused onto the photodetector element. E sig (carrying target echo delay) τ (and the local oscillator optical reference signal with suppressed carrier single-sideband modulation) E LO Beat frequency is generated, and the square-law detection characteristic of the detector is used to achieve wideband radio frequency echo signal mixing and de-skewing reception. Ignoring high-frequency components, the photocurrent signal corresponding to the target echo optical signal is received in the mixing optical domain after de-skewing. I IF ( t Approximately expressed as: in, φ 0 represents the inherent phase difference between the target echo optical signal and the local oscillator optical reference signal. It can be seen that the photocurrent signal retains the target echo time delay information, and its frequency... fIF Only Kτ It is on the order of MHz. K For frequency modulation slope, τ Let t be the target echo delay, and t be time. This is an approximate symbol.

[0031] Therefore, the target echo signal received in the mixed optical domain deslant detection is used to simultaneously detect the azimuth and range of multiple targets. For the azimuth, the spatial azimuth of the target is calculated by the different spot positions of the target echo signal in the photodetector array. For the range, only a low-cost, low-speed analog-to-digital converter 17 is needed to acquire the target echo signal and perform a Fast Fourier Transform (FFT), which is then calculated using the formula... R = c·f IF / 2 K Extract the spatial distance of the target R ,in, f IF The frequency is calculated from the photocurrent signal corresponding to the target echo optical signal. c At the speed of light, K This is the frequency modulation slope. This effectively saves hardware costs when using staring radar to measure the range and angle of arrival of multiple targets within a large field of view.

[0032] like Figure 6 As shown, the embodiment also provides a microwave optical aperture transformation staring reception method with optical domain deslant, which uses the above system and includes the following steps: S1, another light signal is output from the light source module through the local oscillator reference light generation module and generated as a local oscillator optical reference signal by suppressed carrier single-sideband modulation; S2, through the array signal modulation module, modulates the radio frequency echo signals of each channel onto a beam of light signal output by the light source module to form an optical carrier signal and transmits it into free space; S3 extracts a portion of the modulated optical carrier signal through the wavefront repair module for closed-loop compensation of random phase delay errors caused by the optical fiber link.

[0033] S4 acquires target echo light signals with different angles of arrival from free space through an optical Fourier transform module and performs a two-dimensional Fourier transform. S5, the complete target echo light signal output by the optical Fourier transform module is acquired through the photodetector array included in the photodetector detection and acquisition module. At the same time, the local oscillator optical reference signal and the target echo light signal achieve collinear spatial matching on the photosensitive surface of the photodetector array. The two signals beat at the same frequency. The square-law detection characteristic of the photodetector is used to achieve the de-slant reception of the target echo light signal in the mixed optical domain. The target echo light signal received by the de-slant reception in the mixed optical domain is used to simultaneously detect the azimuth and range of multiple targets.

[0034] To verify the effectiveness of the optical domain deslant receiving method of this invention, a system simulation model of a microwave optical aperture change staring radar was constructed. The main simulation parameters were set as follows: the radar transmits a broadband linear frequency modulated signal with a center frequency of 18 GHz, a sweep bandwidth of 1 GHz, and a pulse width of 100 μs. The signal received by the antenna array is electro-optically modulated and then mapped onto a non-periodic spiral (Vogel) fiber array composed of 512 optical fibers for transmission, effectively suppressing spatial grating lobes in a large field of view. The lens focal length is set to 60 mm. Two spatial targets are set in the observation airspace: target 1 (A) is located at an azimuth angle of 50°, an elevation angle of 30°, and a distance of 30 m from the radar; target 2 (B) is located at an azimuth angle of -40°, an elevation angle of -20°, and a distance of 60 m from the radar.

[0035] Figure 7 The simulation results of the two-dimensional light intensity distribution on the focal plane of the lens and the location of its imaging point are shown in Table 1: Table 1 from Figure 7 As shown in Table 1, after the two-dimensional spatial Fourier transform of the optical lens, the broadband echo energy of targets A and B at different angles of arrival is focused and separated at different positions on the focal plane. Figure 7 The green box in the middle marks the theoretical detector positions (PD1 and PD2) calculated based on the scaling mapping relationship, which verifies that the technology can achieve angular separation of space targets and that the positions of the photoelectric detector array elements correspond to specific echo directions.

[0036] Figure 8 and Figure 9 These are the de-skewing results of the output signals from the photodetector array elements (PD1 and PD2) corresponding to target A and target B, respectively. Figure 8 (a) and Figure 9 As can be seen from the time-domain waveform in (a), the high-frequency microwave target echo signal, after being mixed with the local oscillator optical reference signal, has been down-converted to an intermediate frequency signal. Observation Figure 8 (b) and Figure 9 As can be seen from the frequency curve in (b), the original RF echo signal with a bandwidth of up to 1 GHz has been reduced to a single-tone intermediate frequency signal at the output of the photodetector. This means that the system backend does not need a high-speed ADC with a sampling rate on the order of GSa / s. Instead, it can use a low-cost, low-speed ADC to complete data acquisition, which greatly reduces the computing power overhead of processing massive amounts of data.

[0037] Ultimately, by Figure 8 (c) and Figure 9As shown in the distance-power curve in (c), the system can obtain the distance of target A as 30m and the distance of target B as 60m by performing FFT on the intermediate frequency signal, which is completely consistent with the initial settings. This fully demonstrates that the present invention can obtain high-precision target distance information with low hardware cost while realizing wide field of view multi-beam staring.

[0038] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microwave optical aperture transform staring receiver system with optical domain deslant correction, comprising a light source module, an array signal modulation module, and an optical Fourier transform module, wherein, The array signal modulation module is used to modulate the radio frequency echo signals of each channel onto a beam of light signal output by the light source module and then transmit it into free space. The optical Fourier transform module is used to collect target echo light signals with different angles of arrival from free space and perform a two-dimensional spatial Fourier transform. The system is characterized by further including a local oscillator reference light generation module and a photoelectric detection and acquisition module. The local oscillator reference light generation module is used to generate a local oscillator optical reference signal by modulating another beam of light output from the light source module with suppressed carrier single-sideband. The photoelectric detection and acquisition module includes a photoelectric detector array, which is used to acquire the complete target echo light signal output by the optical Fourier transform module through the photoelectric detector array. At the same time, the local oscillator optical reference signal and the target echo light signal achieve collinear spatial matching on the photosensitive surface of the photoelectric detector array. The two signals beat, and the square-law detection characteristic of the photoelectric detector is used to achieve the mixed optical domain deskewing reception of the target echo light signal. The target echo optical signal received by the mixed-frequency optical domain deslant receiver is used to simultaneously detect the azimuth and range of multiple targets.

2. The microwave optical aperture change staring receiving system with optical domain deslant correction according to claim 1, characterized in that, In the array signal modulation module, a modulated optical carrier signal is transmitted into free space via an optical fiber array. The transmitting end face of the optical fiber array adopts a non-periodic spiral optical fiber array based on a golden angle. n The polar coordinate position of the fiber ( ρ n , φ n Satisfies the mathematical relation: in, N For the number of array elements, R max This represents the maximum pole diameter of the spiral fiber array.

3. The microwave optical aperture change staring receiving system with optical domain deskewing according to claim 1, characterized in that, In the optical Fourier transform module, a two-dimensional spatial Fourier transform is performed on the target echo light signal to achieve a scaled-down mapping of the target echo light signal. The scaled-down mapping factor is... S scale for: in, λ o and λ RF These are the wavelengths of the light signal output by the light source module and the target echo light signal, respectively. D o and D RF These are the element spacings of the RF antenna array that receives RF echo signals from each channel and the fiber optic array that transmits modulated optical signals, respectively, in the array signal modulation module.

4. The microwave optical aperture change staring receiving system with optical domain deslant correction according to claim 1, characterized in that, The local oscillator reference light generation module includes a dual parallel Mach-Zehnder modulator and a radar transmission signal. The dual parallel Mach-Zehnder modulator, driven by the radar transmission signal, generates the local oscillator optical reference signal by suppressing carrier single-sideband modulation, ensuring that the local oscillator optical reference signal has only a +1 order sideband in the frequency domain, and its electric field intensity... E Lo ( t It can be approximated as: in, f 0 represents the optical signal frequency. f start The starting frequency of the linear frequency modulated signal. K The frequency modulation slope is t, and time is t. P 0 For optical signal power, This is an approximate symbol.

5. The microwave optical aperture change staring receiving system with optical domain deslant correction according to claim 1, characterized in that, In the photoelectric detection and acquisition module, the photosensitive surface size of the photodetector array element needs to be matched and designed according to the maximum observation field of view of the radar and the broadband diffusion corresponding to the maximum relative sweep bandwidth, so that the optical signal energy after broadband diffusion can be received by the photosensitive surface of the detector array element as much as possible.

6. The microwave optical aperture change staring receiving system with optical domain deskewing according to claim 1, characterized in that, In the photoelectric detection and acquisition module, the photocurrent signal corresponding to the target echo light signal received by the frequency mixing optical domain de-skewing receiver is... I IF ( t Approximately expressed as: in, φ 0 represents the inherent phase difference between the target echo optical signal and the local oscillator optical reference signal. The photocurrent signal retains the target echo time delay information, and its frequency... f IF Only Kτ It is on the order of MHz. K For frequency modulation slope, τ Let t be the target echo delay, and t be time. This is an approximate symbol.

7. The microwave optical aperture change staring receiving system with optical domain deskewing according to claim 1, characterized in that, The target echo optical signal received by the mixed-frequency optical domain de-slant receiver is used to simultaneously detect the azimuth and range of multiple targets, including: For the azimuth angle, the spatial azimuth angle of the target is calculated by the different spot positions of the target echo light signal in the photodetector array; For distance, using the formula R = c·f IF / 2 K Extract the spatial distance of the target R ,in, f IF The frequency is calculated from the photocurrent signal corresponding to the target echo optical signal. c At the speed of light, K This represents the frequency modulation slope.

8. The microwave optical aperture change staring receiving system with optical domain deslant correction according to claim 1, characterized in that, The system also includes a wavefront repair module, which is used to extract the partially modulated optical carrier signal transmitted and emitted into free space by the fiber array, and to use it for closed-loop compensation of random phase delay errors caused by the fiber link.

9. A microwave optical aperture transformation staring reception method with optical domain deslant correction, characterized in that, The method employs the system described in any one of claims 1-8 and includes the following steps: The local oscillator reference light generation module outputs another beam of light signal to the light source module, which is then modulated by suppressed carrier single-sideband to generate a local oscillator optical reference signal. The array signal modulation module modulates the radio frequency echo signals of each channel onto a beam of light output from the light source module to form an optical carrier signal, which is then emitted into free space. The optical Fourier transform module collects target echo light signals with different angles of arrival from free space and performs a two-dimensional spatial Fourier transform. The photodetector array included in the photoelectric detection and acquisition module acquires the complete target echo light signal output by the optical Fourier transform module. At the same time, the local oscillator optical reference signal and the target echo light signal achieve collinear spatial matching on the photosensitive surface of the photodetector array. The two signals beat, and the square-law detection characteristic of the photodetector is used to achieve the de-slant reception of the target echo light signal in the mixed optical domain. The target echo light signal received in the mixed optical domain is used to simultaneously detect the azimuth and range of multiple targets.

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