High frame rate wide area video imaging system and method for frequency scanning radar

Abstract

The application discloses a high-frame-rate wide-area video imaging system and method of a frequency scanning radar, and relates to the field of radar imaging. The system comprises an echo data generation module, an echo data preprocessing module, a DBS imaging processing module and a video splicing module. The echo data generation module is used for formulating parameters of the frequency scanning radar, collecting and generating echo data and storing related data. The echo data preprocessing module is used for receiving data of the echo data generation module, completing accurate adaptation of imaging parameters and efficient reception of data. The DBS imaging processing module is used for finely extracting time-frequency domain features of input data of the echo data preprocessing module, simultaneously performing range dimension pulse compression and azimuth dimension pulse accumulation processing, and generating single-frame imaging results. The video splicing module is used for orderly splicing and integrating the imaging results generated by the DBS imaging processing module. The application realizes high-frame-rate wide-area video imaging effect by fusing the frequency scanning system and the DBS imaging mode, and improves the overall performance and efficiency of the radar system.

Description

Technical Field

[0001] This invention belongs to the field of radar technology and relates to a high frame rate wide-area video imaging system and method for frequency-scanning radar. Background Technology

[0002] Video imaging dynamically displays the imaging results of the monitored area via video, offering good performance in applications such as continuous surveillance, moving target detection, and tracking. Current video imaging solutions typically employ the SAR-GMTI mode. SAR (Synthetic Aperture Radar) provides high-resolution ground observation capabilities, generating detailed and high-quality ground radar images suitable for various terrains and weather conditions. GMTI (Ground Moving Target Indication) enhances the system's reconnaissance capabilities, enabling it to not only detect stationary ground targets but also effectively identify and track moving targets on the ground. This combination makes the SAR-GMTI mode widely applicable in military reconnaissance, border monitoring, and disaster assessment, significantly improving the accuracy and efficiency of ground monitoring. Through this integrated imaging scheme, users can obtain more comprehensive and dynamic ground information, thereby supporting more precise decision-making and actions.

[0003] However, existing technologies cannot easily achieve high frame rate wide-area imaging. The scanning range of ordinary SAR systems cannot easily meet the wide-area requirements, necessitating the use of multi-channel or antenna mechanical scanning, which increases both cost and system complexity, imposing certain limitations on experimental implementation. Regarding traditional operating modes, due to their relatively long pulse coherence accumulation time, neither strip mode nor spotlight mode possesses rapid revisit capability, failing to meet the requirements of high frame rate imaging. Therefore, the SAR-GMTI mode cannot effectively monitor and track long-range targets over wide areas in real time.

[0004] Therefore, it is essential to research video imaging methods that offer high imaging speed, low computational cost, and high frame rate. Frequency scanning array technology, as an innovative intra-pulse beam scanning method, was proposed to expand the beam coverage in the azimuth or elevation dimensions, achieving wide-area imaging capabilities. However, while frequency scanning radar expands the azimuth beam coverage and increases video duration, it also increases imaging time and cost. DBS technology, with its lower computational burden, wide scanning range, and excellent real-time performance and effectiveness, has gained widespread recognition in the industry. Therefore, using fast imaging algorithms such as DBS (Doppler Beam Sharpening) to implement high frame rate wide-area video imaging methods in frequency scanning mode is even more necessary. Summary of the Invention

[0005] This invention aims to provide a high frame rate wide-area video imaging system and method for frequency-scanning radar, and the technical solution adopted is as follows:

[0006] The high frame rate wide-area video imaging system of frequency-scanning radar includes: an echo data generation module, an echo data preprocessing module, a DBS imaging processing module, and a video stitching module;

[0007] The output of the echo data generation module is connected to the input of the echo data preprocessing module, the output of the echo data preprocessing module is connected to the input of the DBS imaging processing module, and the output of the DBS imaging processing module is connected to the input of the video stitching module.

[0008] The echo data generation module is used to determine the parameters of the frequency-scanning radar, collect and generate echo data, and store relevant data.

[0009] The echo data preprocessing module is used to receive data from the echo data generation module, and to complete the accurate adaptation of imaging parameters and efficient data reception.

[0010] The DBS imaging processing module is used to extract the fine time-frequency domain features of the input data of the echo data preprocessing module, and at the same time perform range-dimensional pulse compression and azimuth-dimensional pulse accumulation processing to generate a single-frame imaging result.

[0011] The video stitching module is used to systematically stitch and integrate the imaging results generated by the DBS imaging processing module.

[0012] The high frame rate wide-area video imaging system of frequency-scanning radar also includes a moving target detection and imaging module;

[0013] The input terminal of the moving target detection and imaging module is connected to the output terminal of the echo data preprocessing module, and the output terminal of the moving target detection and imaging module is connected to the input terminal of the DBS imaging processing module.

[0014] The moving target detection and imaging module is used to process relevant information of moving targets in the imaging image and provide supplementary key information about the moving targets.

[0015] In one embodiment of the present invention, the frequency scanning radar employs an intra-pulse azimuth frequency scanning array system;

[0016] The intra-pulse orientation frequency scanning array system constructs a linear array consisting of K uniformly distributed sub-arrays. Each sub-array contains the same number of array elements, and the interval between the array elements is precisely set to half a wavelength.

[0017] All of the subarrays transmit the same basic signal, but with different time delays applied during transmission;

[0018] The difference in time delay is achieved through precise control, which can generate a transmission signal that is coupled between time, frequency, and space.

[0019] By adjusting the frequency of the transmitted signal, the intra-pulse azimuth frequency scanning array system can dynamically control the instantaneous pointing angle of the beam center during the pulse duration.

[0020] In one embodiment of the present invention, the basic signal transmitted by the subarray is a linear frequency modulated signal s. LFM (t), the expression is:

[0021]

[0022] In formula (1), t represents the fast time dimension independent variable, used to represent the propagation time of the electromagnetic signal, T q The pulse duration represents the radar signal, f0 is the center frequency of the signal transmitted by the radar system, and l = B / T q Let rect(t / T) represent the frequency modulation slope of the radar signal, B represent the radar signal bandwidth, and rect(t / T) represent the frequency modulation slope of the radar signal. p ) is a rectangular envelope, and its mathematical expression is:

[0023]

[0024] In one embodiment of the present invention, the arithmetic progression of the time delay is achieved by applying it to each array element within the frequency scanning array;

[0025] For a linear array consisting of K subarrays, if the middle subarray, i.e. the (K+1) / 2th subarray, is selected as the reference subarray;

[0026] The mathematical expression for the signal emitted by the k-th subarray is:

[0027]

[0028] In formula (3), Here is the signal convolution expression, δ(·) is the impulse signal, and τ is the time delay. Under far-field conditions, when the instantaneous squint angle formed by the radar-illuminated target and the frequency-scanning array is θ, the synthesized transmitted signal is expressed as:

[0029]

[0030] In formula (4), ∑(·) is the summation operation, f0 represents the center frequency of the radar system's transmitted signal, λ=c / f0 represents the signal wavelength, d represents the width of the subarray, and E(t,θ) represents the instantaneous radiation pattern synthesized by the frequency sweep array. The analytical expression is:

[0031]

[0032] The peak position of the envelope is represented by the instantaneous beam pointing angle, denoted by θ. p (t) represents the time-dependent instantaneous beam pointing angle. Setting the denominator of formula (5) to zero, we obtain the peak value of the radiation pattern envelope:

[0033] π{τ-dsin[θ p (t)] / c}[f0+l(t-Tp / 2)]=n1·π (6)

[0034] In formula (6), n1 is an integer and is decomposed into a constant part n2 and a variable n3 related to time and strabismus angle. Formula (6) is expressed in terms of time t and strabismus angle θ:

[0035] {τ-dsin[θ p (t)] / c}[f0+l(t-Tp / 2)]=n2+n3(t,sinθ) (7)

[0036] In formula (7):

[0037]

[0038] When the instantaneous beam pointing angle within the pulse varies from -90° to 90°, the time delay between frequency-scanned radar subarrays is τ = 1 / B;

[0039] In practice, the beam scanning range of frequency-scanning radar is usually much smaller than [-90°, 90°]. Therefore, the array delay τ << 1 / B. From formula (9), we know that |n3(t,sinθ)| < 1. When calculating the numerical result of n1, n3 is ignored, and n1 is expressed as:

[0040]

[0041] In formula (10), round(·) is the rounding operation;

[0042] The instantaneous beam pointing angle θ is derived using n1. p (t):

[0043]

[0044] As can be seen from formula (11), the instantaneous beam pointing angle θ of the transmitted signal synthesized by the frequency-scanned radar array is... p (t) is related to the pulse time t, and the pulse time t is related to the transmission frequency. Therefore, the pulse time t, transmission frequency, and pulse instantaneous beam pointing angle correspond one-to-one, achieving a three-dimensional coupling effect of time, frequency, and space.

[0045] In one embodiment of the present invention, the time corresponding to the peak position of the transmitted signal envelope varies with the instantaneous beam pointing angle, as expressed by:

[0046]

[0047] In formula (12), 0 <t p (θ) <T p ;

[0048] The formula for the instantaneous radiation pattern E(t,θ) is quite similar to that of the "Sinc" function, which is expressed as follows:

[0049]

[0050] Analogous to the "Sinc" function for finding the positive and negative roots of the first zero of the pattern expression, assuming and We get: (The first zero point is represented by the positive and negative roots respectively.)

[0051]

[0052] Since the reference transmission signal of the frequency sweep array is a linear frequency modulated signal, the signal bandwidth B is correlated with the azimuth angle θ, as expressed by:

[0053]

[0054] Within one cycle of a pulse signal, the azimuth beam coverage of the frequency scanning array is related to the azimuth angle θ corresponding to the start and end of the pulse. The beam scanning range of the frequency scanning radar is controlled by adjusting the time delay τ between subarrays, the radar system signal carrier frequency f0, and the signal bandwidth B.

[0055] In one embodiment of the present invention, based on the intrapulse instantaneous beam center pointing angle θ p From the expression of (t), it can be seen that when in the normal front-looking radar operating mode, i.e., τ=0, the instantaneous beam center pointing angle θ within the pulse is... p (t) is always equal to 0, at which point there is no frequency scanning effect, and the azimuth beamwidth is θ. 3dB =50.8λ / D a D a The azimuth aperture length of the array;

[0056] Let R B For the shortest slant range, the beam coverage area is [R]. B ·tan(-θ 3dB / 2), R B ·tan(θ 3dB / 2)], for a point target within the scene, the beam coverage time reaches 2R.B ·tan(θ 3dB / 2) / V;

[0057] When the time delay τ is not zero, θ p (t) varies with intrapulse time t;

[0058] When t = 0, the instantaneous pointing angle of the beam center is:

[0059] When t = T p At that time, the instantaneous pointing angle of the beam center is

[0060] By selecting an appropriate time delay τ, the intrapulse beam scanning range can be expanded from that of a typical half-wavelength equidistant linear array. Expanded to azimuth frequency scanning mode

[0061] The beam coverage in azimuth frequency scanning mode is:

[0062]

[0063] Let the azimuth beam coverage width be L, then:

[0064]

[0065] For a point target within the scene, the beam coverage time is:

[0066]

[0067] For a single point within a target scene, the scanning time of a frequency-scanning radar is much longer than that of a conventional, equally spaced linear array front-looking radar.

[0068] In one embodiment of the present invention, the scene center point of the intra-pulse scanning range of the frequency-scanned radar beam is Q0, and the Doppler center frequency is:

[0069]

[0070] In formula (19), f d Proportional to sinθ;

[0071] The Doppler bandwidth of the entire scanning scene is:

[0072]

[0073] In formula (20), since frequency-scanning radar generally adopts a front-side-looking mode, θ = 0, and The beamwidth of the entire intra-pulse scan is interpreted by the DBS algorithm as the Doppler bandwidth Δf of the radar main beam.d For frequency-scanned radar signals, segmentation involves dividing the Doppler bandwidth of the entire intra-pulse scanning range.

[0074] The segmentation rate is determined by the number of pulse signals. If there are N pulse signals h(n) (n = 0, 1, ..., N-1), then the sub-beam azimuth angles after dividing the scanning angle of the entire intra-pulse scanning range are:

[0075]

[0076] In formula (21), Substituting this into the Doppler frequency expression, we obtain the Doppler frequency expression for each sub-beam:

[0077]

[0078] In formula (22),

[0079]

[0080] The coherent accumulation result of N pulses is as follows:

[0081]

[0082] In formula (24), h0(n) = h(n)exp(-j2π·f dc (k)·nT r ), T r Given the pulse repetition period, coherently accumulating N pulses is equivalent to performing an FFT transform on them.

[0083] The high frame rate wide-area video imaging method of frequency-scanning radar, applied to the aforementioned high frame rate wide-area video imaging system, includes the following steps:

[0084] S1: The echo data generation module generates wide-area echo data of the frequency-scanned radar according to specific parameters;

[0085] S2: Perform sub-aperture segmentation on the wide-area echo data to obtain echo data for each frame;

[0086] S3: Perform range pulse compression and azimuth dimension FFT processing on the echo data of each frame to obtain preliminary range Doppler data;

[0087] S4: Perform Doppler unwinding processing on the preliminary distance Doppler data;

[0088] S5: Perform distance migration correction on the Doppler unwrapped echo data to obtain a squared image;

[0089] S6: Perform Doppler frequency modulation compensation on the squared image to obtain the compensated image;

[0090] S7: Perform distance-dimensional IFFT on the compensated image to obtain the DBS imaging result for each frame, and then perform temporal stitching to obtain the static target video imaging result.

[0091] The high frame rate wide-area video imaging method of frequency-scanning radar, applied to the aforementioned high frame rate wide-area video imaging system, includes the following steps:

[0092] S1: The echo data generation module generates wide-area echo data for two channels of frequency-scanned radar according to specific parameters;

[0093] S2: Perform sub-aperture segmentation on the echo data of the two channels to obtain the echo data of each frame;

[0094] S3: Perform range pulse compression and azimuth dimension FFT processing on the echo data of each frame to obtain preliminary range Doppler data;

[0095] S4: Perform Doppler unwinding processing on the preliminary distance Doppler data;

[0096] S5: The DPCA algorithm is used to cancel the echo data after Doppler unwrapping of the two channels, filtering out static target clutter and leaving only moving target information;

[0097] S6: Perform range migration correction on the echo data after DPCA cancellation to obtain a squared image;

[0098] S7: Perform Doppler frequency modulation compensation on the squared image to obtain the compensated image;

[0099] S8: Perform distance-dimensional IFFT on the compensated image to obtain the DBS imaging result for each frame, and then perform temporal stitching to obtain the moving target video imaging result.

[0100] The beneficial effects of this invention are:

[0101] 1. The high frame rate wide-area video imaging system of frequency-scanning radar of the present invention combines the frequency-scanning radar system with the DBS imaging mode, which can expand the imaging range without increasing the complexity of the radar system and achieve high frame rate wide-area video imaging, so as to better monitor and track remote targets in a wide area in real time; the system focuses on the intra-pulse azimuth frequency-scanning radar system, and based on in-depth analysis of the spectral characteristics of its echo signal, uses the DBS imaging algorithm to achieve high frame rate wide-area imaging effect;

[0102] 2. The high frame rate wide-area video imaging method of frequency-scanning radar of the present invention can expand the imaging range through frequency scanning system without relying on multi-channel or mechanical scanning, which saves costs and reduces system complexity. At the same time, it can easily achieve high frame rate imaging through DBS imaging method, so as to better realize real-time monitoring and tracking of remote targets in a wide area. Attached Figure Description

[0103] Figure 1 This is a structural block diagram of the high frame rate wide-area video imaging system of frequency-scanning radar provided in the embodiments of the present invention;

[0104] Figure 2 This is a structural block diagram of a high frame rate wide-area video imaging system for a frequency-scanning radar, including a moving target detection and imaging module, provided in an embodiment of the present invention.

[0105] Figure 3 This is a structural diagram of the intra-pulse orientation-dimensional frequency scanning array provided in an embodiment of the present invention;

[0106] Figure 4 This is the ordinary front-side looking radar geometry provided in the embodiments of the present invention;

[0107] Figure 5 This is the azimuth-dimensional intra-pulse frequency scanning radar geometry provided in the embodiments of the present invention;

[0108] Figure 6 This is a flowchart of the high frame rate wide-area video imaging method (static target scene) for frequency-scanning radar provided in the embodiments of the present invention;

[0109] Figure 7 This is a flowchart of a high frame rate wide-area video imaging method (with target scene) for frequency-scanning radar provided in an embodiment of the present invention. Detailed Implementation

[0110] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0111] This invention proposes a high frame rate wide-area video imaging system for frequency-scanning radar. It combines the frequency-scanning radar system with the DBS imaging mode to achieve a high frame rate wide-area video imaging mode. This method can expand the imaging range without increasing the complexity of the radar system, while achieving high frame rate video imaging, and better monitor and track long-range targets in a wide area in real time.

[0112] See attached document Figure 1The high frame rate wide-area video imaging system of this frequency-scanning radar includes: an echo data generation module, an echo data preprocessing module, a DBS imaging processing module, and a video stitching module. The output of the echo data generation module is connected to the input of the echo data preprocessing module, the output of the echo data preprocessing module is connected to the input of the DBS imaging processing module, and the output of the DBS imaging processing module is connected to the input of the video stitching module.

[0113] This invention focuses on the intra-pulse azimuth frequency scanning radar system. Based on an in-depth analysis of the spectral characteristics of its echo signal, it uses the DBS imaging algorithm to achieve high frame rate and wide-area imaging effect.

[0114] Echo data generation module: This module is primarily responsible for parameter setting of the frequency-scanning radar, acquiring and generating echo data, and properly storing the relevant data. As the starting point of the entire process, this module provides the foundation for subsequent processing.

[0115] Echo data preprocessing module: Receives data from the echo data generation module and is responsible for tasks such as accurate adaptation of imaging parameters and efficient data reception, ensuring that the input data meets the requirements of subsequent processing.

[0116] DBS Imaging Processing Module: In this module, the time-frequency domain features of the input data are extracted in detail, and a series of complex processes such as range pulse compression and azimuth pulse accumulation are performed to generate a single-frame imaging result, which is a key link in building high frame rate imaging.

[0117] Video stitching module: It takes each frame of imaging results generated by the DBS imaging processing module as input, and stitches and integrates the imaging results of all frames in an orderly manner according to specific rules, and finally successfully constructs a high frame rate wide-area video imaging result, realizing the key transformation from single frame to video imaging.

[0118] The above-mentioned frequency-scanning radar high frame rate wide-area imaging is a static scene imaging mode. The present invention also provides a moving target scene imaging mode including a moving target detection and imaging module.

[0119] See attached document Figure 2 The high frame rate wide-area video imaging system for frequency-scanning radar provided by this invention includes an echo data generation module, an echo data preprocessing module, a DBS imaging processing module, a video stitching module, and a moving target detection and imaging module. The input terminal of the moving target detection and imaging module is connected to the output terminal of the echo data preprocessing module, and the output terminal of the moving target detection and imaging module is connected to the input terminal of the DBS imaging processing module.

[0120] Moving Target Detection and Imaging Module: Focuses on processing information related to moving targets in the imaging image, using specific algorithms to accurately detect moving targets in the imaging image, and performing targeted processing on them, providing key information about moving targets to the entire imaging system.

[0121] This invention combines a frequency scanning radar system with a DBS imaging mode to achieve a high frame rate wide-area video imaging mode. It can expand the imaging range without increasing the complexity of the radar system, while achieving high frame rate video imaging, and better monitor and track long-range targets in a wide area in real time.

[0122] This invention relates to a frequency-scanning radar system employing an intra-pulse azimuth frequency scanning array system. This system constructs a linear array consisting of K uniformly distributed subarrays. Each subarray contains the same number of array elements, and the spacing between these elements is precisely set to half a wavelength. This is done to prevent grating lobes in the radiation pattern, thereby preventing interference with the echo signal. All subarrays transmit the same reference signal, but they are subject to different time delays during transmission. This difference in time delay is achieved through precise control, enabling the generation of a transmitted signal that is coupled in time, frequency, and space. By adjusting the signal frequency, the system can dynamically control the instantaneous pointing angle of the beam center within the pulse duration. To achieve the time delay between subarrays, the system employs actual physical delay circuitry. A structural diagram of the intra-pulse azimuth frequency scanning array is attached. Figure 3 As shown.

[0123] Linear frequency modulation signal s LFM (t) is chosen as the basic signal transmitted by each subarray during azimuth frequency scanning due to its constant envelope characteristics and ease of generation in hardware.

[0124] Linear frequency modulation signal s LFM The expression for (t) is:

[0125]

[0126] In formula (1), t represents the fast time dimension independent variable, used to represent the propagation time of the electromagnetic signal, T q The pulse duration represents the radar signal, f0 is the center frequency of the signal transmitted by the radar system, and l = B / T q Let rect(t / T) represent the frequency modulation slope of the radar signal, B represent the radar signal bandwidth, and rect(t / T) represent the frequency modulation slope of the radar signal. p ) is a rectangular envelope, and its mathematical expression is:

[0127]

[0128] By applying equal time delays to each element within the frequency scanning array, a frequency scanning signal can be generated, achieving the effect of frequency scanning. For a transmitting array consisting of K subarrays, and based on the attached... Figure 3 If the middle subarray, i.e., the (K+1) / 2th subarray, is selected as the reference subarray in the described frequency scanning array architecture, then the specific mathematical expression of the signal emitted by the kth subarray under this setting can be described as follows:

[0129]

[0130] In formula (3), Here is the signal convolution expression, δ(·) is the impulse signal, and τ is the time delay. Under far-field conditions, when the instantaneous squint angle formed by the radar-illuminated target and the frequency-scanning array is θ, the synthesized transmitted signal is expressed as:

[0131]

[0132] In formula (4), ∑(·) is the summation operation, f0 represents the center frequency of the radar system's transmitted signal, λ=c / f0 represents the signal wavelength, d represents the width of the subarray, and E(t,θ) represents the instantaneous radiation pattern synthesized by the frequency sweep array. The analytical expression is:

[0133]

[0134] As can be seen from the instantaneous radiation pattern expression of the frequency-scanned radar array obtained above, the peak position of the envelope can be represented by the instantaneous beam pointing angle. Using θ... p (t) represents the time-dependent instantaneous beam pointing angle. Setting the denominator of formula (5) to zero, we obtain the peak value of the radiation pattern envelope:

[0135] π{τ-dsin[θ p (t)] / c}[f0+l(t-Tp / 2)]=n1·π (6)

[0136] In formula (6), n1 is an integer and is decomposed into a constant part n2 and a variable n3 related to time and strabismus angle. Therefore, formula (6) is expressed in terms of time t and strabismus angle θ:

[0137] {τ-dsin[θ p (t)] / c}[f0+l(t-Tp / 2)]=n2+n3(t,sinθ) (7)

[0138] In formula (7):

[0139]

[0140] When the instantaneous beam pointing angle within a pulse varies from -90° to 90°, the time delay between the subarrays of the frequency-scanning radar is τ = 1 / B. In practice, the beam scanning range of a frequency-scanning radar is usually much smaller than [-90°, 90°], so the array time delay τ << 1 / B. From formula (9), we know that |n3(t,sinθ)| < 1. When calculating the numerical result of n1, n3 is ignored, and n1 is expressed as:

[0141]

[0142] In formula (10), round(·) is the rounding operation.

[0143] The instantaneous beam pointing angle θ is derived using n1. p (t):

[0144]

[0145] As can be seen from formula (11), the instantaneous beam pointing angle θ of the transmitted signal synthesized by the frequency-scanned radar array is... p (t) is related to the pulse time t, and the pulse time t is related to the transmission frequency. Therefore, the pulse time t, transmission frequency, and pulse instantaneous beam pointing angle correspond one-to-one, achieving a three-dimensional coupling effect of time, frequency, and space.

[0146] According to formula (11), we can deduce in reverse the change of time corresponding to the peak position of the transmitted signal envelope with the instantaneous pointing angle of the beam, as expressed in the following expression:

[0147]

[0148] In formula (12), 0 <t p (θ) <T p .

[0149] The formula for the instantaneous radiation pattern E(t,θ) is quite similar to that of the "Sinc" function, which is expressed as follows:

[0150]

[0151] Therefore, analogous to the "Sinc" function solving for the positive and negative roots of the first zero of the pattern expression, assuming... and We get: (The first zero point is represented by the positive and negative roots respectively.)

[0152]

[0153] Since the reference transmission signal of the frequency sweep array is a linear frequency modulated signal, the signal bandwidth B is correlated with the azimuth angle θ, as expressed by:

[0154]

[0155] Within one cycle of a pulse signal, the azimuth beam coverage of the frequency scanning array is related to the azimuth angle θ corresponding to the start and end times of the pulse. According to formula (15), the beam scanning range of the frequency scanning radar can be controlled by adjusting the inter-array delay τ, the radar system signal carrier frequency f0, and the signal bandwidth B.

[0156] The geometric structure of a conventional equidistant linear array radar with frontal and side views is shown in the attached diagram. Figure 4 As shown in the attached diagram, the geometric structure of the azimuth-based intra-pulse frequency scanning radar is as follows. Figure 5 As shown.

[0157] Based on the instantaneous beam center pointing angle θ within the pulse p From the expression of (t), it can be seen that when in the normal front-looking radar operating mode, i.e., τ=0, the instantaneous beam center pointing angle θ within the pulse is... p (t) is always equal to 0, at which point there is no frequency scanning effect, and the azimuth beamwidth is θ. 3dB =50.8λ / D a D a is the azimuth aperture length of the array.

[0158] Let R B For the shortest slant range, the beam coverage area is [R]. B ·tan(-θ 3dB / 2), R B ·tan(θ 3dB / 2)], for a point target within the scene, the beam coverage time reaches 2R. B ·tan(θ 3dB / 2) / V.

[0159] When the time delay τ is not 0, we can notice that θ p (t) will change with the intrapulse time t. That is, the intrapulse time t∈[0,T] for each pulse. p This corresponds to a signal transmission frequency and simultaneously to the azimuth pointing angle of an instantaneous beam. The time-frequency-space three-dimensional coupling enables azimuth-dimensional intra-pulse frequency scanning.

[0160] When t = 0, the instantaneous pointing angle of the beam center is:

[0161] When t = T p At that time, the instantaneous pointing angle of the beam center is

[0162] By selecting an appropriate time delay τ, the intrapulse beam scanning range can be expanded from that of a typical half-wavelength equidistant linear array. Expanded to azimuth frequency scanning mode

[0163] The beam coverage in azimuth frequency scanning mode is:

[0164]

[0165] Let the azimuth beam coverage width be L, then:

[0166]

[0167] For a point target within the scene, the beam coverage time is:

[0168]

[0169] For a single point within a target scene, the scanning time of a frequency-scanning radar is significantly longer than that of a conventional, equally spaced linear array front-looking radar. For radar video imaging systems, azimuth-based frequency scanning can effectively expand the video monitoring range and extend the monitoring time of the target scene, achieving a wide-area scanning effect without relying on hardware limitations.

[0170] As attached Figure 5 As shown, the scene center point of the intra-pulse scanning range of the frequency-scanned radar beam is Q0, and the Doppler center frequency is:

[0171]

[0172] In formula (19), f d Proportional to sinθ;

[0173] The Doppler bandwidth of the entire scanning scene is:

[0174]

[0175] In formula (20), since frequency-scanning radar generally adopts a front-side-looking mode, θ = 0, and The beamwidth of the entire intra-pulse scan is interpreted by the DBS algorithm as the Doppler bandwidth Δf of the radar main beam. d For frequency-scanned radar signals, segmentation involves dividing the Doppler bandwidth of the entire intra-pulse scanning range.

[0176] The segmentation rate is determined by the number of pulse signals. If there are N pulse signals h(n) (n = 0, 1, ..., N-1), then the sub-beam azimuth angles after dividing the scanning angle of the entire intra-pulse scanning range are:

[0177]

[0178] In formula (21), Substituting this into the Doppler frequency expression, we obtain the Doppler frequency expression for each sub-beam:

[0179]

[0180] In formula (22),

[0181]

[0182] The coherent accumulation result of N pulses is as follows:

[0183]

[0184] In formula (24), h0(n) = h(n)exp(-j2π·f dc (k)·nT r ), T r Let N be the pulse repetition period. It can be seen that coherent accumulation of N pulses is equivalent to performing a Fast Fourier Transform (FFT) on them.

[0185] DBS technology can quickly monitor a wide area of ​​the ground and obtain ground radar images of this large area, effectively improving the angular resolution within the radar detection area. Its coherent pulse accumulation time is relatively short and the computational load is not large, making it easy to achieve high frame rate imaging effects.

[0186] The frequency-scanning radar high frame rate wide-area imaging of this invention can be divided into two modes: static scene imaging mode and scene imaging mode containing moving targets. Different processing procedures are used for the two modes.

[0187] For static scene imaging modes, refer to the appendix. Figure 6 The high frame rate wide-area video imaging method of frequency-scanning radar of the present invention includes the following steps:

[0188] S1: The echo data generation module generates wide-area echo data of the frequency-scanned radar according to specific parameters;

[0189] S2: Perform sub-aperture segmentation on the wide-area echo data, determine the sub-aperture length based on the frame rate, and obtain the echo data for each frame;

[0190] S3: Perform range pulse compression and azimuth FFT processing on the echo data of each frame to obtain preliminary range Doppler data. However, the data still has Doppler entanglement at this time and cannot initially show the imaging results.

[0191] S4: Perform Doppler unwinding processing on the range Doppler data. Since the Doppler bandwidth of the system itself is greater than the pulse repetition frequency, there will be a problem of spectral overlap. Therefore, it is necessary to eliminate the echo entanglement relationship in the frequency sweep system, which can expand the Doppler bandwidth to prevent Doppler blurring. At this time, the echo spectrum no longer has the Doppler entanglement relationship, and the preliminary imaging results can be obtained.

[0192] S5: After the previous step, the imaging results will be curved due to the distance migration problem. Therefore, it is necessary to perform distance migration correction on the Doppler unwrapped echo data in order to obtain a squared image.

[0193] S6: At this point, the image cannot be well focused, so Doppler frequency modulation compensation is performed on the squared image to compensate for the phase error caused by the cumulative effect of the aircraft motion, which can further improve the image resolution and imaging effect, and obtain the compensated image.

[0194] S7: Perform a distance-dimensional fast inverse Fourier transform (IFFT) on the compensated image to obtain the DBS imaging result for each frame, and then perform time-series stitching to obtain the static target video imaging result.

[0195] For imaging modes of scenes containing moving targets, refer to the appendix. Figure 7 The high frame rate wide-area video imaging method of frequency-scanning radar of the present invention includes the following steps:

[0196] S1: The echo data generation module generates wide-area echo data for two channels of frequency-scanned radar according to specific parameters;

[0197] S2: Perform sub-aperture segmentation on the echo data of the two channels respectively, determine the sub-aperture length according to the frame rate, and obtain the echo data of each frame;

[0198] S3: Perform range pulse compression and azimuth FFT processing on the echo data of each frame to obtain preliminary range Doppler data. However, the data still has Doppler entanglement at this time and cannot initially show the imaging results.

[0199] S4: Perform Doppler unwinding processing on the preliminary range Doppler data. Since the Doppler bandwidth of the system itself is greater than the pulse repetition frequency, there will be a problem of spectral overlap. Therefore, it is necessary to eliminate the echo entanglement relationship in the frequency sweep system, which can expand the Doppler bandwidth to prevent Doppler blurring. At this time, the echo spectrum no longer has the Doppler entanglement relationship, and the preliminary imaging results can be obtained.

[0200] S5: The offset antenna phase center (DPCA) algorithm is used to cancel the echo data after Doppler unwrapping of the two channels, filtering out the static target clutter and leaving only the moving target information.

[0201] S6: After the previous step, the imaging results will be curved due to the distance migration problem. Therefore, it is necessary to perform distance migration correction on the echo data after DPCA cancellation in order to obtain a squared image.

[0202] S7: At this point, the image cannot be well focused, so Doppler frequency modulation compensation is performed on the squared image to compensate for the phase error caused by the cumulative effect of the aircraft motion, which can further improve the image resolution and imaging effect, and obtain the compensated image.

[0203] S8: Perform distance-dimensional IFFT on the compensated image to obtain the DBS imaging result for each frame, and then perform temporal stitching to obtain the moving target video imaging result.

[0204] This invention presents a high frame rate wide-area video imaging method for frequency-scanning radar. It combines frequency scanning with deep focus scanning (DBS) imaging to achieve high frame rate wide-area video imaging results. The frequency scanning system expands the imaging range without requiring multi-channel or mechanical scanning, saving costs and reducing system complexity. Simultaneously, the DBS imaging method easily achieves high frame rate imaging, enabling better real-time monitoring and tracking of long-range targets over wide areas. Furthermore, it significantly improves the overall performance and efficiency of the radar system in multiple dimensions. This groundbreaking technological innovation undoubtedly opens a new path for the application and development of radar systems, providing a more reliable, efficient, and flexible solution for real-time monitoring and tracking tasks in numerous fields.

[0205] Specifically, the introduction of frequency scanning technology allows radar systems to scan different directions by adjusting the frequency of the transmitted signal without increasing hardware complexity, thereby achieving comprehensive coverage of a wide area. This feature not only expands the radar's imaging range but also improves the continuity and stability of imaging, providing a solid foundation for real-time monitoring.

[0206] Meanwhile, by combining the DBS imaging method, this frequency-scanning radar's high frame rate wide-area video imaging method further improves the frame rate of radar video imaging. DBS technology utilizes the Doppler effect to process radar echo signals, thereby achieving rapid target acquisition. This high frame rate imaging capability enables the radar system to more quickly identify and track long-range targets over a wide area, providing strong support for decision-making.

[0207] In summary, the high frame rate wide-area video imaging method of frequency-scanning radar of this invention, by combining frequency scanning system with DBS imaging mode, brings revolutionary changes to the application and development of radar systems. It will provide more reliable, efficient, and flexible real-time monitoring and tracking solutions for numerous fields such as military reconnaissance, air traffic control, meteorological observation, and disaster early warning, driving the continuous advancement of radar technology.

[0208] The above description is merely a specific example of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, can make various modifications and adjustments to its form and details without departing from the principles and structure of the present invention. However, these modifications and adjustments based on the concept of the present invention are still within the scope of protection of the claims of the present invention. For example, one possible alternative is to process the echo data of the two channels separately and then use the space-time two-dimensional adaptive processing (STAP) algorithm as a method for static target clutter cancellation. This method is similar to the idea of ​​using the DPCA algorithm for static target clutter cancellation in the present invention, and is analogous to the present invention, and is still within the scope of protection of the claims of the present invention.

Claims

1. A high frame rate wide area video imaging system for a frequency scanning radar, characterized in that, The system comprises an echo data generation module, an echo data preprocessing module, a DBS imaging processing module and a video splicing module. The output end of the echo data generation module is connected with the input end of the echo data preprocessing module, the output end of the echo data preprocessing module is connected with the input end of the DBS imaging processing module, and the output end of the DBS imaging processing module is connected with the input end of the video splicing module. The echo data generation module is used for formulating parameters of a frequency scanning radar, collecting and generating echo data and storing the echo data. The echo data preprocessing module is used for receiving data of the echo data generation module, completing accurate adaptation of imaging parameters and efficient reception of data. The DBS imaging processing module is used for finely extracting time-frequency domain features of input data of the echo data preprocessing module, simultaneously performing range dimension pulse compression and azimuth dimension pulse accumulation processing, and generating a single frame of imaging results. The Doppler bandwidth of the whole scanning scene is: The scene center point of the frequency-sweep radar beam intra-pulse scanning range is , and the Doppler center frequency is: （19） In equation (19), is proportional to ; represents the velocity of the motion of the frequency scanning radar; represents the wavelength of the signal, represents the center frequency of the signal transmitted by the radar system; is the instantaneous squint angle of the target illuminated by the radar and the frequency scanning array; is the propagation speed of light in vacuum; In formula (22), （20） In equation (20), since the frequency scanning radar adopts the forward-looking mode, so and is the beam width of the entire intra-pulse scanning, where is the instantaneous pointing angle of the beam center when is the instantaneous pointing angle of the beam center when is the instantaneous pointing angle of the beam center when is the instantaneous pointing angle of the beam center when represents the fast time dimension variable, which is used to represent the time of electromagnetic signal propagation; is the azimuth beam width; The DBS algorithm is for dividing the Doppler bandwidth of a radar main beam For a frequency-swept radar signal, the Doppler bandwidth of the entire intra-pulse sweep range is divided. The segmentation rate is determined by the number of pulse signals. If there are pulse signals , , the instantaneous squint angle of the sub-beam after the scanning angle of the entire intra-pulse scanning range is segmented is: （21） In equation (21), Bringing this into the Doppler frequency expression, the Doppler frequency expression for each sub-beam is obtained: （22） The video splicing module is used for orderly splicing and integrating imaging results generated by the DBS imaging processing module. （23） The coherent accumulation result of one pulse is: ​ （24） In equation (24), , is the pulse repetition period, and the coherent accumulation of N pulses is equivalent to an FFT transform. The system further comprises a moving target detection and imaging module.

2. The high frame rate wide area video imaging system for frequency scanning radar of claim 1, wherein, The input end of the moving target detection and imaging module is connected with the output end of the echo data preprocessing module, and the output end of the moving target detection and imaging module is connected with the input end of the DBS imaging processing module. The moving target detection and imaging module is used for processing related information of dynamic targets in an imaging graph, and providing key information supplement of the dynamic targets. The frequency scanning radar adopts an intra-pulse azimuth dimension frequency scanning array system.

3. The high frame rate wide area video imaging system for frequency scanning radar of claim 1 or 2, wherein, All the sub-arrays emit the same basic signal, and different time delays are applied when the basic signal is emitted. The intra-pulse azimuth direction frequency scanning array system constructs a linear array composed of a plurality of uniformly distributed sub-arrays Each of the sub-arrays comprises a same number of array units, and intervals between the array units are accurately set as half of a wavelength. The difference of the time delays is realized by accurate control, and a kind of transmission signal with mutual coupling of time, frequency and space can be generated. By adjusting the frequency of the transmission signal, the intra-pulse azimuth dimension frequency scanning array system can dynamically control the instantaneous pointing angle of the beam center within the pulse duration. The difference of the time delays is realized by applying different time delays to each array unit inside the frequency scanning array.

4. The high frame rate wide area video imaging system for frequency scanning radar of claim 3, wherein, The basic signal emitted by the sub-array is a chirp signal The expression is: （1） In equation (1), represents the fast time dimension variable, which is used to represent the time of electromagnetic signal propagation, represents the pulse duration of the radar signal, is the center frequency of the radar system transmitted signal, represents the frequency modulation slope of the radar signal, represents the radar signal bandwidth, is a rectangular envelope, the mathematical expression is: （2）。 5. The high frame rate wide area video imaging system for frequency scanning radar of claim 4, wherein, In formula (7), For a linear array composed of sub-arrays, if the middle sub-array, i.e., the sub-array, is selected as the reference sub-array; No. The mathematical expression for the signals emitted by each subarray is as follows: （3） In formula (3), " " is the signal convolution expression, It is an impulse signal. For time delay, Under far-field conditions, when the instantaneous squint angle formed by the radar-illuminated target and the frequency-scanning array is... At that time, the synthesized transmitted signal is represented as: （4） In equation (4), for the summation operation, denotes the center frequency of the radar system transmit signal, represents the signal wavelength, denotes the width of the subarray, denotes the imaginary unit; denotes the instantaneous pattern of the frequency scanning array synthesis, which is given by （5） The peak position of the envelope is expressed in terms of the instantaneous beam pointing angle, denoted by denotes the time-dependent instantaneous beam pointing angle, the peak of the pattern envelope is obtained by setting the denominator of equation (5) to zero: （6） In formula (6) is an integer and is decomposed into a constant part and a variable dependent on time and squint angle Formula (6) is expressed in terms of time and squint angle ​ （7） The time corresponding to the peak position of the transmission signal envelope changes with the instantaneous pointing angle of the beam, and the expression is: （8） （9） When the intra-pulse transient beam pointing angle varies from -90° to 90°, the time delay between the frequency-scan radar sub-arrays is ; The beam scanning range of the frequency scanning radar is greater than -90° and less than 90°, so the array time delay From formula (9), In calculating the numerical results of , the is ignored, is expressed as: （10） In equation (10), is a rounding operation; By deriving the instantaneous beam pointing angle : （11） From formula (11), it can be seen that the intra-pulse instantaneous beam pointing angle of the transmitting signal synthesized by the frequency-sweep radar array is related to the intra-pulse time , and the intra-pulse time is related to the transmitting frequency, so the intra-pulse time , the transmitting frequency and the intra-pulse instantaneous beam pointing angle correspond to each other, achieving a time-frequency-space three-dimensional coupling effect.

6. The high frame rate wide area video imaging system for frequency scanning radar of claim 5, wherein, The beam coverage range in the azimuth dimension frequency scanning mode is: （12） In equation (12), ; The function expression is:​ （13） Analogies The positive and negative roots of the first zero of the directional pattern expression are solved by the function and are the positive and negative roots of the first zero, respectively, and we have （14） Since the reference transmitting signal of the frequency sweeping array is a linear frequency modulation signal, the signal bandwidth with the instantaneous squint angle with the correlation, the expression is: （15） The azimuth beam coverage of the frequency scanning array in one cycle of the pulse signal is the instantaneous squint angle corresponding to the beam at the start and end time of the pulse The beam scanning range of the frequency scanning radar is adjusted by adjusting the time delay between the subarrays The signal carrier frequency of the radar system and the signal bandwidth are controlled.

7. The high frame rate wide area video imaging system for frequency scanning radar of claim 6, wherein, According to the instantaneous intra-pulse beam center pointing angle The expression can be known that when in the normal side-looking radar working mode, i.e. The instantaneous intra-pulse beam center pointing angle Is equal to 0, at this time, there is no frequency scanning effect, and the azimuth beam width is , wherein Is the array azimuth aperture length; Let The coverage of the beam is For a point target within the scene, the beam coverage time is , denotes the speed of the frequency scanning radar; When the time delay is not 0, varies with the intra-pulse time of variation; When the beam center instantaneous pointing angle is ; When the beam center instantaneous pointing angle is ; Selecting a preset time delay After that, the intrapulse beam scanning range can be expanded from the half-wavelength equidistant linear array corresponding to to the azimuth dimension frequency scanning mode ; For a point target in the scene, the beam coverage time is: （16） Let the azimuthal dimension beam coverage width be Then: （17） For a point in the target scene, the scanning time of the frequency scanning radar is much greater than that of the ordinary equidistant linear array positive side-looking radar. （18） The system is applied to the high frame rate wide area video imaging system as claimed in claim 1, and comprises the following steps:

8. A high frame rate wide area video imaging method for frequency scanning radar, characterized in that, S1: The echo data generation module generates wide area echo data of the frequency scanning radar according to specific parameters; S2: The wide area echo data is sub-aperture segmented to obtain echo data of each frame; S3: The echo data of each frame is subjected to range pulse compression and azimuth dimension FFT processing to obtain preliminary range Doppler data; S4: The preliminary range Doppler data is subjected to Doppler unwrapping processing; S5: The echo data after Doppler unwrapping is subjected to range migration correction to obtain a square image. ​ S6: compensating the Doppler frequency of the square image to obtain a compensated image; S7: performing distance dimension IFFT on the compensated image to obtain DBS imaging results of each frame, and then performing time sequence splicing to obtain static target video imaging results.

9. A high frame rate wide area video imaging method for frequency scanning radar, characterized in that, The application is applied to the high frame rate wide area video imaging system as claimed in claim 2, and comprises the following steps: S1: an echo data generation module generates wide area echo data of a frequency scanning radar of two channels according to specific parameters; S2: each frame of echo data is obtained by performing sub-aperture segmentation on the echo data of two channels respectively; S3: distance pulse compression and azimuth dimension FFT processing are performed on the echo data of each frame to obtain preliminary distance Doppler data; S4: Doppler unwrapping processing is performed on the preliminary distance Doppler data; S5: DPCA algorithm is adopted to cancel the echo data of two channels after the Doppler unwrapping processing, so as to filter out static target clutter and only leave dynamic target information; S6: distance migration correction is performed on the echo data after the DPCA cancellation to obtain a square image; S7: the Doppler frequency of the square image is compensated to obtain a compensated image; S8: distance dimension IFFT is performed on the compensated image to obtain DBS imaging results of each frame, and then time sequence splicing is performed to obtain dynamic target video imaging results.

Images