A method and system for simultaneously realizing spotlight and strip SAR imaging using a coded array

Abstract

The present invention relates to a method and system for realizing beamforming and strip SAR imaging simultaneously with a coded array, the method comprising: arranging a radar array along the azimuth direction of SAR imaging, assigning a separate coded pulse signal to each radiating element of the radar array; the separate coded pulse signal enables the echo signal generated by the target reflection to be separable in time, space or frequency; or the echo signal can be separated after decoding processing; when the radar is working, each radiating element of the radar array transmits its own coded pulse signal, and each radiating element receives the echo signal of the coded pulse signal transmitted by itself and other radiating elements; collecting the echo signal received by each radiating element, and performing decoding processing; according to the decoded echo signal, performing beamforming and strip SAR imaging processing simultaneously, and obtaining beamforming and strip SAR imaging results simultaneously. The present invention realizes the working method and system requirements of the synthetic aperture radar of two imaging modes at the same time, and improves the imaging efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and in particular relates to a method and a system for simultaneously realizing beamforming and strip SAR imaging with a coded array. Background Art

[0002] Synthetic aperture radar (SAR) can achieve high-resolution imaging of targets. SAR uses pulse compression to improve range resolution and synthetic aperture to improve azimuth resolution.

[0003] Synthetic aperture radar has different imaging modes, including strip imaging, beam imaging, etc. Figure 1 shown.

[0004] In the prior art, strip SAR imaging is the earliest and most widely used SRA imaging mode. The imaging area of ​​strip SAR imaging is a long strip area parallel to the moving direction of the carrier aircraft (or carrier platform such as satellite). Usually, the radar beam is perpendicular to the flight track, that is, it is looking straight sideways, and it can also work in the oblique mode. However, in the imaging process, under ideal conditions, the angle between the radar beam and the flight track remains unchanged. The azimuth resolution of the strip SAR imaging mode is limited by the size of the radar antenna, that is, it cannot be better than half the length of the azimuth antenna. In actual system design, it is impossible to reduce the size limit of the azimuth antenna indefinitely. Therefore, improving the azimuth resolution of SAR is limited.

[0005] In the prior art, the spotlight SAR imaging mode provides a method for improving azimuth resolution. During the imaging process, by controlling the radar beam to point to the same area, the target can be observed within a larger viewing angle, increasing the accumulation time of the synthetic aperture in a small area. This in turn improves the azimuth resolution, making it no longer limited by the azimuth size of the antenna.

[0006] However, spotlight SAR imaging can only perform high-resolution azimuth imaging of small areas and cannot image continuous strips of the ground on one side of the flight track like strip SAR imaging, which reduces imaging efficiency.

[0007] Therefore, there is a need in the art for a synthetic aperture radar working method and system that can overcome the limitations of traditional strip SAR imaging in improving azimuth resolution and the shortcomings of spotlight SAR imaging that cannot achieve continuous imaging and high-efficiency observation, and can simultaneously realize two imaging modes. Summary of the invention

[0008] In view of the above analysis, the present invention aims to disclose a method and system for realizing simultaneous imaging and detection by a coded array, so as to overcome the shortcomings of traditional imaging radar and moving target detection radar and meet the requirements for improving the system performance of realizing simultaneous radar imaging and detection.

[0009] The present invention discloses a method for realizing simultaneous beamforming and strip SAR imaging using a coded array, comprising the following steps:

[0010] The radar array is arranged along the azimuth of SAR imaging, and a separate coded pulse signal is assigned to each radiating element of the radar array; the separate coded pulse signal enables the echo signal generated by the target reflection to be separated in time, space or frequency; or the echo signal can be separated after decoding processing;

[0011] When the radar is working, each radiating element of the radar array transmits its own coded pulse signal, and each radiating element receives the echo signal of the coded pulse signal transmitted by itself and other radiating elements;

[0012] The echo signal received by each radiation array element is collected and decoded; according to the decoded echo signal, the beamforming and strip SAR imaging processing are performed simultaneously, and the beamforming and strip SAR imaging results are obtained simultaneously.

[0013] Furthermore, the spotlight SAR imaging processing uses the target echo signal of the non-synchronous coded pulse signal of each array element to form a virtual spotlight imaging scanning beam to obtain virtual spotlight scanning radar data; and then uses the data to perform spotlight SAR imaging processing to obtain a spotlight SAR image.

[0014] Furthermore, the strip SAR imaging processing uses the target echo signal of the non-synchronous coded pulse signal of each array element to form a virtual strip imaging beam to obtain virtual strip imaging radar data, and then uses the data to perform strip SAR imaging processing to obtain a strip SAR image.

[0015] Further, the separate coded pulse signal is a frequency-divided coded pulse signal, a time-phase combined coded pulse signal or a time-phase-frequency combined coded pulse signal;

[0016] The separate coded pulse signal is a frequency-divided coded pulse signal; when transmitting, each array element transmits at a different frequency, and the transmission channel is isolated by frequency; when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated by frequency domain filtering;

[0017] The separate coded pulse signal is a time-phase combined coded pulse signal, and the basic constraint of coding is that the coding channels are orthogonal to each other; when transmitting, each array element uses different coding for transmission; when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated through decoding processing;

[0018] The separate coded pulse signal is a time-phase-frequency combined coded pulse signal, and the basic constraint of coding is that the coding channels are orthogonal to each other; when transmitting, each array element uses different coding for transmission; when receiving, after each array element receives the echo signal, the echo signals corresponding to the transmission signals of different array elements are separated through decoding processing.

[0019] Furthermore, the collecting the echo signal received by each radiation array element and performing decoding processing includes:

[0020] For the frequency-division coded pulse signal, the decoding process is performed by frequency domain filtering;

[0021] For the time-phase combined coded pulse signal, a decoding matrix is ​​obtained through the coding matrix, and then the echo signal is decoded using the decoding matrix; the decoding matrix corresponds to the coding matrix, including a pulse decoding mode corresponding to the pulse coding mode of all array elements;

[0022] For the time-phase-frequency combined coded pulse signal, the decoding matrix is ​​obtained through the coding matrix, and then the decoding matrix is ​​used to process the echo signal; the echo signal is then decoded and processed in combination with the frequency filtering method; the decoding matrix corresponds to the coding matrix, including the pulse decoding method corresponding to the pulse coding method of all array elements.

[0023] Furthermore, in the spotlight SAR imaging process,

[0024] For the decoded N 2 The target echo data of independent channel signals are selected for subsequent processing according to the imaging resolution, where N is the number of array elements; including:

[0025] 1) Frequency processing:

[0026] For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0027] For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0028] For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0029] 2) Beamforming Processing:

[0030] According to the imaging distance and imaging range, the synthetic beam width θ is determined; according to the synthetic beam width θ, the number of array elements involved in the imaging process is determined; according to the azimuth resolution ρ of the beamforming imaging a According to the requirements, determine the beam imaging angle θ s ;

[0031] The starting and ending positions of the beamforming are calculated according to the imaging center position, the distance between the radar and the imaging center, and the beamforming imaging angle. From the starting position of the beamforming to the ending position of the beamforming, the instantaneous beamforming pointing angle is calculated at each sampling position during the radar flight process.

[0032] For each sampling position, the instantaneous pointing angle of the beam at that position is used to determine the phase shift of each array element involved in the beam synthesis processing. The data obtained by each array element at that position is phase corrected, and then the data corresponding to the same moment from different array elements are accumulated to complete the beam synthesis. The virtual beam scanning radar data of the radar at that position is obtained through synthesis.

[0033] Furthermore, the synthetic beam width L is the length of the ground imprint irradiated by the radar beam at the imaging distance perpendicular to the wave propagation direction; R max The farthest imaging distance;

[0034] The number of array elements for beam synthesis is determined based on the antenna beam width corresponding to the antenna length determined by the number of array elements being not less than the synthesized beam width θ;

[0035] The beam imaging angle Where λ is the wavelength of the center frequency of the transmitted signal.

[0036] Furthermore, in the strip SAR imaging process,

[0037] For the decoded N 2 The target echo data of independent channel signals are selected for subsequent processing according to the imaging resolution, where N is the number of array elements; including:

[0038] 1) Frequency processing:

[0039] For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0040] For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0041] For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0042] 2) Beamforming Processing:

[0043] According to the azimuth resolution ρ of strip SAR imaging a The number of array elements involved in the imaging process is determined according to the requirements; the number of array elements used for beam synthesis is determined by the antenna length determined by the number of array elements being no greater than half of the azimuth resolution;

[0044] For each sampling position, the phase shift phase of each array element participating in the beam synthesis processing is determined by using the instantaneous pointing angle of the beam at the position, and the phase correction is performed on the data obtained by each array element at the position. Then, the data corresponding to the same time of different array elements are accumulated to complete the beam synthesis, and the virtual strip imaging radar data of the radar at the position is obtained by synthesis;

[0045] 3) Imaging processing:

[0046] The virtual strip imaging radar data obtained by synthesis is used to perform SAR strip imaging processing to obtain a strip SAR image.

[0047] The present invention also discloses a system for realizing a method for simultaneously realizing a spotlighting and a strip SAR imaging method based on the coded array as described above, comprising:

[0048] An array coded signal generating unit, used to generate a separate pulse coded signal emitted by each radiating array element; the separate coded pulse signal enables the echo signal generated by the target reflection to be separable in time, space or frequency; or the echo signal can be separated after decoding processing;

[0049] A radar array includes N array elements, each array element transmits a pulse coded signal, and receives target echo signals transmitted by all array elements with pulse coded signals;

[0050] A data acquisition unit, used for acquiring target echo signals received by each radiation array element to form target echo data;

[0051] The array signal decoding and processing unit is used to decode the collected target echo data and separate the N corresponding to the combination of transceiver channels formed by different radiation array elements. 2 Target echo data of independent channel signals;

[0052] A virtual beam forming unit is used to calculate the target echo data corresponding to different transceiver channel combinations to generate a virtual spotlight imaging scanning beam and a virtual strip imaging beam, and process the target echo data to obtain virtual spotlight scanning radar data and virtual strip imaging radar data;

[0053] A spotlight SAR imaging processor is used to perform imaging processing based on virtual spotlight scanning radar data to obtain a spotlight SAR image;

[0054] The strip SAR image processor is used for performing imaging processing according to virtual strip imaging radar data to obtain a strip SAR image.

[0055] Furthermore, it also includes a comprehensive display unit, which is used to perform visualization processing on the spotlight SAR image and the strip SAR image to form a video stream including the spotlight SAR image and the strip SAR image and their information;

[0056] The control unit is used to control the coding array to realize the signal generation, transmission and reception, acquisition, processing and display data generation of the simultaneous imaging system.

[0057] The present invention can achieve at least one of the following beneficial effects:

[0058] (1) The present invention can simultaneously acquire radar data that can be used for strip SAR imaging and spotlight SAR imaging, thereby improving the efficiency of imaging.

[0059] (2) The present invention can simultaneously acquire strip SAR images and spotlight SAR images of a continuous observation area.

[0060] (3) The azimuth resolution of the spotlight SAR images simultaneously acquired by the present invention is not limited by the overall physical size of the array antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0062] Figure 1 Schematic diagram of the working mode of strip and spotlight SAR imaging according to the prior art;

[0063] Figure 2 A schematic diagram of a method for simultaneously implementing spotlighting and strip SAR imaging in an embodiment of the present invention;

[0064] Figure 3 is a schematic diagram of simultaneously implementing spotlight beamforming in an embodiment of the present invention;

[0065] Figure 4 Schematic diagram of a SAR imaging radar system that simultaneously implements spotlighting and strip SAR imaging in an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used to illustrate the principles of the present invention together with the embodiments of the present invention.

[0067] One embodiment of the present invention discloses a method for realizing simultaneous spotlighting and strip SAR imaging using a coded array. Figure 2 As shown, the following steps are included:

[0068] Step S1, the radar array is arranged along the azimuth direction of SAR imaging, and a separate coded pulse signal is assigned to each radiating element of the radar array;

[0069] The separate coded pulse signal enables the echo signal generated by the target reflection to be separable in time, space or frequency; or the echo signal is separable after being decoded.

[0070] Preferably, the separate coded pulse signal is a frequency-divided coded pulse signal. When transmitting, each array element transmits at a different frequency, and the transmission channel is isolated by frequency. When receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated by frequency domain filtering;

[0071] Preferably, the separate coded pulse signal is a time-phase combined coded pulse signal, and the basic constraint of coding is that the coding channels are orthogonal to each other. When transmitting, each array element uses different coding to transmit, and when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated through decoding processing;

[0072] Preferably, the separate coded pulse signal is a time-phase-frequency combined coded pulse signal, the basic constraint of the coding is that the coding channels are orthogonal to each other, and each array element uses different coding for transmission. When receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated through decoding processing;

[0073] Step S2: When the radar is working, each radiating element of the radar array transmits its own coded pulse signal;

[0074] Specifically, according to assigning a separate coded pulse signal to each radiating element of the radar array, each radiating element of the radar array transmits its own coded pulse signal.

[0075] Step S3, the radar array receives the echo signal of the coded pulse;

[0076] Each radiating array element receives the echo signal of its own transmitted coded pulse signal and the echo signal of the coded pulse signal transmitted by other radiating array elements; and solves the problem of interference of transmitted signals between channels through frequency isolation or codec isolation.

[0077] Step S4, collecting the echo signal received by each radiation array element, and decoding the echo signal;

[0078] For the frequency-division coded pulse signal, the decoding process is performed by frequency domain filtering;

[0079] For the time-phase combined coded pulse signal, the decoding matrix is ​​obtained through the coding matrix, and then the decoding matrix is ​​used to process the echo signal to complete the decoding process;

[0080] For the time-phase-frequency combined coded pulse signal, the decoding matrix is ​​obtained through the coding matrix, and then the decoding matrix is ​​used to process the echo signal, and the decoding process is completed in combination with the frequency filtering method.

[0081] Step S5, performing spotlight and strip SAR imaging processing simultaneously according to the decoded echo signal, and obtaining spotlight and strip SAR imaging results simultaneously;

[0082] Specifically, the spotlight SAR imaging method includes:

[0083] The target echo signal of each array element's non-synchronous coded pulse can be used to form a virtual spotlight imaging scanning beam to obtain virtual spotlight scanning radar data, which is then used to perform spotlight SAR imaging processing to obtain a spotlight SAR image. The specific processing includes:

[0084] For decoded echo data, including N 2 The data of the signals of independent channels (N is the number of array elements) are selected according to the imaging resolution to carry out subsequent processing:

[0085] 1) Frequency processing:

[0086] For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0087] For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0088] For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0089] 2) Beamforming Processing:

[0090] Figure 3 is a schematic diagram of simultaneously implementing spotlight beamforming in an embodiment of the present invention;

[0091] According to the requirements of imaging distance and imaging range, the synthetic beam width θ is determined. The length L of the ground imprint irradiated by the radar beam at the imaging distance perpendicular to the wave propagation direction is calculated from the synthetic beam width θ and the farthest imaging distance R max Determined, The length L should not be less than the line connecting any two points within the imaging range, that is,

[0092] According to the requirement of the above-mentioned synthetic beam width θ, the number of array elements participating in the imaging process is determined. The antenna beam width corresponding to the antenna length determined by the number of array elements used for beam synthesis must be no less than the requirement of the synthetic beam width θ, thereby determining the number of array elements used for beam synthesis.

[0093] According to the azimuth resolution ρ of the spotlight imaging a According to the requirements, determine the beam imaging angle θ s , Where λ is the wavelength of the center frequency of the transmitted signal.

[0094] The starting and ending positions of the beamforming are calculated according to the imaging center position, the distance between the radar and the imaging center, and the beamforming imaging angle. From the starting position of the beamforming to the ending position of the beamforming, the instantaneous pointing angle of the beamforming is calculated at each sampling position during the radar flight.

[0095] For each sampling position, the instantaneous pointing angle of the beam at that position is used to determine the phase shift of each array element involved in the beam synthesis processing. The data obtained by each array element at that position is phase corrected, and then the data corresponding to the same moment from different array elements are accumulated to complete the beam synthesis. The virtual beam scanning radar data of the radar at that position is obtained through synthesis.

[0096] 3) Imaging processing:

[0097] The virtual spotlight scanning radar data at different positions from the spotlight starting position to the spotlight ending position obtained by synthesis are used to perform spotlight SAR imaging processing to obtain a spotlight SAR image.

[0098] Specifically, the strip SAR imaging method includes:

[0099] The target echo signal of each array element's non-synchronous coded pulse can be used to form a virtual strip imaging beam to obtain virtual strip imaging radar data, which is then used to perform strip SAR imaging processing to obtain a strip SAR image. The specific processing includes:

[0100] For decoded echo data, including N 2 The data of the signals of independent channels (N is the number of array elements) are selected according to the imaging resolution to carry out subsequent processing:

[0101] 1) Frequency processing:

[0102] For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0103] For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0104] For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement;

[0105] 2) Beamforming Processing:

[0106] According to the azimuth resolution ρ of strip SAR imaging a The number of array elements involved in the imaging process is determined according to the requirements. The antenna length determined by the number of array elements used for beam synthesis is not greater than half of the azimuth resolution, thereby determining the number of array elements used for beam synthesis.

[0107] For each sampling position, the instantaneous pointing angle of the beam at that position (90° for positive side-view imaging) is used to determine the phase shift of each array element involved in the beam synthesis processing, and the phase correction is performed on the data obtained by each array element at that position. Then, the data corresponding to the same moment from different array elements are accumulated to complete the beam synthesis, and the virtual strip imaging radar data of the radar at that position is obtained through synthesis.

[0108] 3) Imaging processing:

[0109] The virtual strip imaging radar data obtained by synthesis is used to perform SAR strip imaging processing to obtain a strip SAR image.

[0110] Step S6, performing comprehensive display processing on the radar image and the target detection result;

[0111] Step S7: Display the integrated display-processed radar image and moving target information on a display device.

[0112] Another embodiment of the present invention discloses a coded array to realize simultaneous spotlighting and strip SAR imaging system, such as Figure 4 As shown, including:

[0113] An array coding signal generating unit, configured to generate a separate pulse coding signal transmitted by each radiating array element;

[0114] The individual coded signals are separable from the echo signals generated by the coded signals at the target in time, space or frequency, or by a decoding process.

[0115] The radar array includes N array elements arranged along the azimuth of SAR imaging; each array element transmits a pulse coded signal and receives the target echo signal transmitted by all array elements; each array element also includes a transmitter, a receiver and a circulator corresponding to the transmitter, the receiver and the array element, respectively, for transmitting the radiation signal output by the transmitter to the array element for radiation, or outputting the target echo signal received by the array element to the receiver for receiving and processing. And the circulator realizes the radar's transmission and reception isolation.

[0116] Each array element of the radar array should have the ability to transmit an independent coded signal when transmitting, and should have the ability to independently receive an echo signal when receiving.

[0117] Connected to the transmitter of each array element is a separate pulse coded signal corresponding to the array element generated by the array coded signal generating unit;

[0118] Connected to the receiver output of each array element is a data acquisition unit;

[0119] A data acquisition unit is configured to acquire a target echo signal received by each radiation array element to form target echo data;

[0120] The data acquisition unit may acquire the echo signal of each array element separately, or mix the echo signals of N array elements (N>1) and then acquire the mixed signal.

[0121] The array signal decoding and processing unit is configured to decode the collected target echo data and separate the target echo data corresponding to the combination of transceiver channels formed by different radiation array elements;

[0122] For frequency division coding, the echo data collected corresponding to the echo signal received by each array element is subjected to frequency domain filtering by the filter group corresponding to the number of array elements, and each filter outputs an echo signal corresponding to the frequency of the transmitting array element;

[0123] For time-phase combined coding, the echo data collected corresponding to the echo signal received by each array element is operated with the decoding matrix to obtain an output decoding signal corresponding to the number of array elements.

[0124] For time-phase-frequency combined coding, the echo data collected corresponding to the echo signal received by each array element is operated with the decoding matrix and subjected to frequency domain filtering to obtain an output decoding signal corresponding to the number of array elements.

[0125] A virtual beam forming unit is configured to calculate and generate a virtual spotlight imaging scanning beam and a virtual strip imaging beam for target echo data corresponding to different transceiver channel combinations, and process and obtain virtual spotlight scanning radar data and virtual strip imaging radar data;

[0126] An imaging processor is configured to perform imaging processing on target echo data corresponding to different transceiver channel combinations to obtain a spotlight SAR image and a strip SAR image;

[0127] Since it is necessary to perform spotlight SAR imaging processing and strip SAR imaging processing simultaneously, and the data sources of these two processing are different, the imaging processing machine includes two independent signal processors, namely, a spotlight SAR imaging processor and a strip SAR image processor.

[0128] According to the specific application environment and different requirements of real-time processing, the virtual beamforming unit and imaging processor can use general commercial computers, industrial computers, or a dedicated signal processing platform composed of signal processing boards composed of multiple DSPs, FPGAs, etc.

[0129] An integrated display unit is configured to perform visualization processing on the spotlight SAR image and the strip SAR image to form a video stream including the spotlight SAR image and the strip SAR image and information thereof;

[0130] The control unit is configured to control the coding array to realize signal generation, transmission and reception, acquisition, processing and display data generation of the simultaneous spotlight and strip SAR imaging system.

[0131] The control unit generates system working synchronization signals, including signal generation synchronization signals, signal acquisition synchronization signals, and transceiver protection synchronization signals. Each array element has independent signal generation synchronization signals, signal acquisition synchronization signals, and transceiver protection synchronization signals. The signal generation synchronization signals and signal acquisition synchronization signals corresponding to each array element must maintain a strict synchronization relationship, and the synchronization requirements are no less than the time synchronization requirements for SAR imaging.

[0132] It should be noted that in order to make the embodiments of the present invention easier to understand, the above description omits some more specific technical details that are well known to those skilled in the art and may be necessary for the implementation of the embodiments of the present invention. For example, the above description omits a general description of an existing radar or radar system. It should be understood that the continuous pulse radar according to the embodiment of the present invention may also have other components or assemblies that an existing radar or radar system has in addition to the transmitter, receiver and signal restorer described above. The above description is merely illustrative and not restrictive.

[0133] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for simultaneously realizing spotlighting and strip SAR imaging using a coded array, characterized in that: The following steps are involved: The radar array is arranged along the azimuth of SAR imaging, and a separate coded pulse signal is assigned to each radiating element of the radar array; the separate coded pulse signal enables the echo signal generated by the target reflection to be separated in time, space or frequency; or the echo signal can be separated after decoding processing; When the radar is working, each radiating element of the radar array transmits its own coded pulse signal, and each radiating element receives the echo signal of the coded pulse signal transmitted by itself and other radiating elements; Collecting the echo signal received by each radiation array element and performing decoding processing; According to the decoded echo signal, spotlight and strip SAR imaging processing are performed simultaneously to obtain spotlight and strip SAR imaging results; The separate coded pulse signal is a frequency-divided coded pulse signal, a time-phase combined coded pulse signal or a time-phase-frequency combined coded pulse signal; The separate coded pulse signal is a frequency-divided coded pulse signal; when transmitting, each array element transmits at a different frequency, and the transmission channel is isolated by frequency; when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated by frequency domain filtering; The separate coded pulse signal is a time-phase combined coded pulse signal, and the basic constraint of coding is that the coding channels are orthogonal to each other; when transmitting, each array element uses different coding for transmission; when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated through decoding processing; The separate coded pulse signal is a time-phase-frequency combined coded pulse signal, and the basic constraint of coding is that the coding channels are orthogonal to each other; when transmitting, each array element uses different coding for transmission; when receiving, after each array element receives the echo signal, the echo signal corresponding to the transmission signal of different array elements is separated through decoding processing; The collecting the echo signal received by each radiation array element and performing decoding processing includes: For the frequency-division coded pulse signal, the decoding process is performed by frequency domain filtering; For the time-phase combined coded pulse signal, a decoding matrix is ​​obtained through the coding matrix, and then the echo signal is decoded using the decoding matrix; the decoding matrix corresponds to the coding matrix, including a pulse decoding mode corresponding to the pulse coding mode of all array elements; For the time-phase-frequency combined coded pulse signal, a decoding matrix is ​​obtained through the coding matrix, and then the echo signal is processed using the decoding matrix; the echo signal is decoded and processed in combination with the frequency filtering method; the decoding matrix corresponds to the coding matrix, including a pulse decoding method corresponding to the pulse coding method of all array elements; In the spotlight SAR imaging process, For the decoded N 2 The target echo data of independent channel signals are selected for subsequent processing according to the imaging resolution, where N is the number of array elements; including: 1) Frequency processing: For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; 2) Beamforming Processing: According to the imaging distance and imaging range, the synthetic beam width θ is determined; according to the synthetic beam width θ, the number of array elements involved in the imaging process is determined; according to the azimuth resolution ρ of the beamforming imaging a According to the requirements, determine the beam imaging angle θ s ; The starting and ending positions of the beamforming are calculated according to the imaging center position, the distance between the radar and the imaging center, and the beamforming imaging angle. From the starting position of the beamforming to the ending position of the beamforming, the instantaneous beamforming pointing angle is calculated at each sampling position during the radar flight process. For each sampling position, the phase shift of each array element participating in the beamforming process is determined using the instantaneous beamforming pointing angle of the sampling position, and the phase of the data obtained by each array element at the sampling position is corrected. Then, the data corresponding to the same time of different array elements are accumulated to complete the beamforming, and the virtual beamforming scanning radar data of the radar at the sampling position is obtained through synthesis; The resultant beamwidth L is the length of the ground imprint irradiated by the radar beam at the imaging distance perpendicular to the wave propagation direction; R max The farthest imaging distance; The number of array elements for beam synthesis is determined based on the antenna beam width corresponding to the antenna length determined by the number of array elements being not less than the synthesized beam width θ; The beamforming angle Where λ is the wavelength of the center frequency of the transmitted signal.

2. The method according to claim 1, characterized in that The spotlight SAR imaging process uses the target echo signal of the non-synchronous coded pulse signal of each array element to form a virtual spotlight imaging scanning beam to obtain virtual spotlight scanning radar data; and then uses the data to perform spotlight SAR imaging process to obtain a spotlight SAR image.

3. The method according to claim 1, characterized in that The strip SAR imaging process uses the target echo signal of the non-synchronous coded pulse signal of each array element to form a virtual strip imaging beam to obtain virtual strip imaging radar data, and then uses the data to perform strip SAR imaging process to obtain a strip SAR image.

4. The method according to claim 1, characterized in that In strip SAR imaging processing, For the decoded N 2 The target echo data of independent channel signals are selected for subsequent processing according to the imaging resolution, where N is the number of array elements; including: 1) Frequency processing: For frequency division coding, after filtering the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; For time-phase combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; For time-phase-frequency combined coding, after filtering and decoding the received data, frequency synthesis is performed, and the frequency bandwidth after synthesis is not less than the frequency bandwidth corresponding to the imaging resolution requirement; 2) Beamforming Processing: According to the azimuth resolution ρ of strip SAR imaging a The number of array elements involved in the imaging process is determined according to the requirements; the number of array elements used for beam synthesis is determined by the antenna length determined by the number of array elements being no greater than half of the azimuth resolution; For each sampling position, the phase shift phase of each array element participating in the beam synthesis processing is determined by using the instantaneous pointing angle of the beam at the sampling position, and the phase correction is performed on the data obtained by each array element at the sampling position. Then, the data corresponding to the same time of different array elements are accumulated to complete the beam synthesis, and the virtual strip imaging radar data of the radar at the sampling position is obtained by synthesis; 3) Imaging processing: The virtual strip imaging radar data obtained by synthesis is used to perform SAR strip imaging processing to obtain a strip SAR image.

5. A system for simultaneously implementing a spotlight and strip SAR imaging method based on the coded array according to any one of claims 1 to 4, characterized in that: include: An array coding signal generating unit, used for generating a separate pulse coding signal emitted by each radiating array element; The separate coded pulse signal enables the echo signal generated by the target reflection to be separated in time, space or frequency; or the echo signal can be separated after decoding processing; A radar array includes N array elements, each array element transmits a pulse coded signal, and receives target echo signals transmitted by all array elements with pulse coded signals; A data acquisition unit, used for acquiring target echo signals received by each radiation array element to form target echo data; The array signal decoding and processing unit is used to decode the collected target echo data and separate the N corresponding to the combination of transceiver channels formed by different radiation array elements. 2 Target echo data of independent channel signals; A virtual beam forming unit is used to calculate and generate a virtual spotlight imaging scanning beam and a virtual strip imaging beam for target echo data corresponding to different transceiver channel combinations, and process and obtain virtual spotlight scanning radar data and virtual strip imaging radar data; A spotlight SAR imaging processor is used to perform imaging processing based on virtual spotlight scanning radar data to obtain a spotlight SAR image; The strip SAR image processor is used for performing imaging processing according to virtual strip imaging radar data to obtain a strip SAR image.

6. The system according to claim 5, characterized in that Also includes, An integrated display unit, used for visualizing the spotlight SAR image and the strip SAR image to form a video stream including the spotlight SAR image and the strip SAR image and their information; The control unit is used to control the signal generation, receiving and sending, acquisition, processing and display data generation of the coding array system to achieve simultaneous imaging.

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