A method and system for imaging a frequency agile waveform forward looking radar with jitter phase compensation

Abstract

This invention discloses a frequency-agile waveform forward-looking radar imaging method and system with jitter phase compensation, comprising the following steps: transmitting multiple pulse signals in a completely random frequency-agile manner; wherein each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; receiving the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; performing range pulse compression processing on the echo signal of each wave position; performing range travel correction on the range pulse compressed signal; performing jitter phase compensation on the range travel corrected echo signal; and performing angle super-resolution imaging processing on the jitter phase compensated echo signals of different wave positions. The multi-dimensional random agile design of carrier frequency and pulse repetition frequency gives the radar transmitted signal a high degree of randomness and non-periodicity, improving the radar's survivability in complex electromagnetic environments.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology, and particularly relates to a frequency-agile waveform forward-looking radar imaging method and system with jitter phase compensation. Background Technology

[0002] Forward-looking radar imaging enables high-resolution observation and target detection of the area in front of a platform in complex weather and battlefield environments, and has significant application value in fields such as airborne guidance and aircraft landing. Currently, most traditional forward-looking imaging radars adopt a fixed carrier frequency or a small-range frequency stepping operating mode, maintaining a constant carrier frequency or only slowly varying it within a narrow band on the transmitted waveform to ensure the phase coherence of the echo signal and the invariance of the target scattering amplitude, which facilitates azimuth focusing and high-resolution imaging through conventional imaging algorithms.

[0003] In interference-free electromagnetic environments, fixed carrier frequency systems can meet basic forward-looking radar imaging requirements. However, in complex adversarial scenarios, the drawbacks of this operating mode become apparent: on the one hand, fixed carrier frequency signals have a single frequency domain characteristic and their spectrum remains unchanged over a long period, making them extremely vulnerable to interception, identification, and locking by enemy electronic reconnaissance equipment, thus suffering from noise suppression and deception interference from false targets; on the other hand, due to the long-term fixed frequency point, interference energy can be highly concentrated within the radar's operating frequency band, resulting in a significant decrease in the radar echo signal-to-noise ratio, and causing severe noise pollution, target defocusing, and imaging ghosting during imaging processing.

[0004] To enhance anti-jamming capabilities, forward-looking radar systems introduce a stepped or random stepped frequency agility mechanism. This mechanism achieves intra-group carrier frequency jumps through waveform dwell time, broadening the signal frequency domain coverage and disrupting the coherent accumulation conditions of interfering signals, thereby reducing interference effectiveness. However, the intra-group stepped frequency waveform contains only one set of agile frequency points. The limited spectral broadening and strong regularity of the agility restrict anti-jamming effectiveness. Furthermore, traditional stepped-frequency forward-looking imaging algorithms all require the use of large-bandwidth synthesis technology to achieve high-resolution imaging in the range dimension. The large-bandwidth synthesis algorithm for each waveform has high computational complexity, making it difficult for forward-looking imaging algorithms for stepped-frequency signals to effectively balance anti-jamming and imaging processing delays. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a frequency-agile waveform forward-looking radar imaging method and system with jitter phase compensation. By employing a multi-dimensional random agile design of carrier frequency and pulse repetition frequency, the radar transmitted signal exhibits high randomness and non-periodicity, significantly reducing the probability of the signal being intercepted and identified by the enemy. It can also effectively counter electronic interference based on coherent relay, thereby enhancing the radar's survivability in complex electromagnetic environments.

[0006] To achieve the above objectives, the technical solution of the present invention is: a frequency-agile waveform forward-looking radar imaging method with jitter phase compensation, comprising the following steps: Multiple pulse signals are transmitted in a completely random frequency agile manner; each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; Receive the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; Range pulse compression processing is performed on the echo signal of each wave position; Perform distance travel correction on the signal after distance pulse compression; Perform jitter phase compensation on the echo signal after distance travel correction; Angular super-resolution imaging processing was performed on the echo signals of different wave positions after jitter phase compensation.

[0007] In a preferred embodiment, each transmitted pulse signal is represented as: in, This represents the m-th pulse signal. This represents a rectangular gate function, where T represents the pulse width. t represents the frequency modulation slope, and t represents the fast time. Let i be the carrier frequency of the m-th pulse. This represents the frequency hopping interval of the m-th pulse. The starting frequency point; Each wavelength contains two pulse signals, and the two pulse signals of the same wavelength have the same carrier frequency element.

[0008] In a preferred embodiment, the echo signal received from the target at the m-th wave position is represented as: in, This represents the echo signal corresponding to the pulse signal with the same carrier frequency at the m-th position, where m takes values ​​from 1 to M. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. Indicates the slant range between the target and the radar. , The radial velocity of the target, The initial distance between the target and the radar is represented by t, which represents the fast time. This represents the slow time of the i-th pulse at the m-th position. Indicates echo delay, 'c' represents the azimuth angle, and 'c' represents the speed of light.

[0009] In a preferred embodiment, range pulse compression processing for the echo signal at each wave position further includes: Perform a distance-to-Fourier transform on the echo signal to transform the signal to the frequency domain; Construct a pulse compression matching function, and use the pulse compression matching function to perform frequency domain pulse compression processing on the signal after range-to-frequency domain transformation; The signal after distance pulse compression processing is: in, This represents the range pulse compressed signal corresponding to the selected m-th pulse signal with the same carrier frequency, where m ranges from 1 to M. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. Indicates the slant range between the target and the radar. , The radial velocity of the target relative to the radar platform. The initial distance between the target and the radar is represented by t, which represents the fast time. This represents the slow time of the i-th pulse at the m-th position. Indicates echo delay, 'c' represents the azimuth angle, and 'c' represents the speed of light. This indicates the frequency point corresponding to a fast time t.

[0010] In a preferred embodiment, performing distance travel correction processing on the signal after distance pulse compression further includes: Construct a travel correction filter function, and use the travel correction filter function to perform range travel correction processing on the signal after range pulse compression processing; Perform a range-direction inverse Fourier transform on the signal after range travel correction to transform the signal into the time domain; The signal after the inverse Fourier transform of the distance is represented as: in, This represents the distance-corrected signal corresponding to the selected m-th pulse signal with the same carrier frequency. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. This indicates the initial distance between the target and the radar. Let represent the slow time of the i-th pulse at the m-th wave position, c represent the speed of light, and t represent the fast time.

[0011] In a preferred embodiment, jitter phase compensation is performed on the distance-corrected echo signal, including: Construct a jitter Doppler phase compensation function, and use the jitter Doppler phase compensation function to perform jitter Doppler phase compensation processing on all pulses after distance movement correction processing; Construct a jitter initial phase compensation filter from the first echo signal after jitter Doppler phase compensation processing of each pulse position. The jitter initial phase compensation filter is used to compensate the jitter initial phase of the second pulse echo signal after jitter Doppler compensation processing of the wave position echo signal to achieve jitter initial phase compensation for each wave position echo signal. The echo signal after initial phase compensation for the jitter at the m-th position is represented as: in, This represents the echo signal after initial phase compensation for the jitter of the m-th wave position. Let m be the target scattering coefficient. This represents the target antenna amplitude gain at the m-th position. This represents the azimuth angle of the m-th beam, and t represents the fast time. The slow time of the m-th wave position is represented by γ, the frequency modulation slope is represented by γ, and the pulse width is represented by T. This represents the slant range between the target and the radar at the m-th wave position observation. The initial distance between the target and the radar is represented by , and c represents the speed of light.

[0012] In a preferred embodiment, angular super-resolution imaging processing is performed on the echo signals of different wave positions after initial phase compensation for jitter, including: Construct an observation matrix of the squared sampled values ​​of the two-way antenna pattern; Based on the probability distributions of the target and noise, the imaging process is transformed into a convex optimization problem of the maximum likelihood function. The target scattering coefficient is estimated by solving the convex optimization problem of the maximum likelihood function using a sparse Bayes-based convex optimization algorithm. The final imaging result is obtained based on the estimated scattering coefficient.

[0013] In a preferred embodiment, the observation matrix for constructing the squared sample values ​​of the two-way antenna pattern is represented as: ; Where A represents the squared observation matrix of the two-way antenna pattern samples. This represents the first sampled value of the radar two-way antenna pattern. This represents the Mth sampled value of the radar two-way antenna pattern.

[0014] Based on the same concept, the present invention also provides a frequency-agile waveform forward-looking radar imaging system with jitter phase compensation, comprising: The signal transmission module is used to transmit multiple pulse signals in a completely random frequency agile manner; wherein each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; The signal receiving module is used to receive the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; The pulse compression module is used to perform distance pulse compression processing on the echo signal of each wave position; The distance travel correction module is used to perform distance travel correction on the signal after distance pulse compression. The phase compensation module is used to perform jitter phase compensation on the echo signal after distance travel correction; The imaging module is used to perform angular super-resolution imaging processing on echo signals of different wave positions after jitter phase compensation.

[0015] Based on the same concept, the present invention also provides a readable storage medium storing a processing program, which, when executed by a processor, implements the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation as described above.

[0016] Based on the same concept, the present invention also provides an electronic device, characterized in that it includes: a memory for storing a processing program; and a processor, which, when executing the processing program, implements the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation as described above.

[0017] Based on the same concept, the present invention also provides a readable storage medium, characterized in that the readable storage medium stores a processing program, which, when executed by a processor, implements the frequency agile waveform forward-looking radar imaging method with jitter phase compensation as described above.

[0018] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art: By employing a multidimensional random agile design of carrier frequency and pulse repetition frequency (PRF), the radar transmitted signal exhibits high randomness and non-periodicity. This significantly reduces the probability of signal interception and identification by the enemy and effectively counters electronic interference based on coherent relay, enhancing the radar's survivability in complex electromagnetic environments. It also solves the problem of phase continuity disruption in multidimensional agile waveforms when detecting "extended targets" (i.e., targets occupying multiple range cells). Through a two-step method of "coarse compensation + fine compensation," the Doppler phase shift caused by differences in scattering point positions is accurately corrected, achieving efficient coherent accumulation. Attached Figure Description

[0019] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a flowchart illustrating a frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to the present invention. Figure 2 This is a schematic diagram of the frequency distribution of a completely random frequency-agile waveform provided in an embodiment of the present invention; Figure 3 A schematic diagram of the initial positions of five points measuring 10 meters by 10 meters provided in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the effect of traditional imaging methods. Figure 5 This is a schematic diagram illustrating the effect of step-frequency imaging. Figure 6 This is a schematic diagram illustrating the imaging method provided in an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0021] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0022] The inventors discovered that using a completely random frequency-agile signal, compared to traditional linear frequency modulated (LFM) and stepped-frequency agile signals, is more effective at combating range or angle deception interference and some narrowband modulation noise interference, ensuring that the radar maintains stable and reliable imaging capabilities even in complex electromagnetic environments. Secondly, compared to stepped-frequency agile signals, it eliminates the need for long beam dwell times to ensure identical pulse carrier frequencies for each wave position, avoiding the drawbacks of complex, large-bandwidth synthesis techniques used per wave position to achieve high range resolution. Therefore, this invention, addressing the need for high-resolution imaging in complex electromagnetic environments, considers applying a completely random frequency-agile signal to forward-looking super-resolution imaging. This significantly reduces the signal dwell time and imaging processing requirements for forward-looking radar compared to stepped-frequency signals, while also improving the anti-interference capabilities of traditional LFM and stepped-frequency signal-based radar systems.

[0023] Example like Figure 1 As shown, a frequency-agile waveform forward-looking radar imaging method with jitter phase compensation is provided, which specifically includes the following steps: S10: Transmits multiple pulse signals in a completely random frequency agile manner; wherein, each wave position contains two pulse signals, the pulse signals of the same wave position have the same carrier frequency, and the pulse signals of different wave positions have different carrier frequencies.

[0024] The signal transmitted by the completely random frequency agility method makes the carrier frequency information of each wave position completely different, which greatly expands the spectrum information of the transmitted signal. The signal has high randomness and therefore has excellent anti-signal sorting and anti-interference capabilities.

[0025] The design employs a completely random frequency agility, grouping pulse signals by one wave position, with each group containing only two pulse signals of the same carrier frequency. The carrier frequency design for different wave positions during the radar observation time is completely different. The forward-looking radar antenna scans and resides on M wave positions in the observation area, with each wave position containing two pulse signals. Each pulse is a linear frequency modulated signal with the same carrier frequency. Correspondingly, each transmitted wave position pulse signal is represented as: (1) in, This represents the m-th pulse signal. This represents a rectangular gate function, where T represents the pulse width. t represents the frequency modulation slope, and t represents the fast time. Let i be the carrier frequency of the m-th pulse. This represents the frequency hopping interval of the m-th pulse. This is the starting frequency point. Each wave position contains two pulse signals, and the two pulse signals at the same wave position have the same carrier frequency element.

[0026] Here, m ranges from 1 to M; each pulse position consists of two pulse signals with the same carrier frequency, but the carrier frequencies of the pulse signals in each pulse position are different. For example, the carrier frequencies of the two pulse signals in the first pulse position are both 4.8 × 10⁻⁶. 8 Hz; the carrier frequency of both pulse signals in the second phase is 15.6 × 10⁻⁶. 8 Hz; the carrier frequency of both pulse signals in the third phase is 5.7 × 10⁻⁶. 8 Hz; the carrier frequency of both pulse signals in the fourth phase is 9.6 × 10⁻⁶. 8 Hz; pulse signals at other wavelengths are similar and will not be described further here.

[0027] S20: Receives the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position.

[0028] In these M pulse signals, assuming all pulse signals scan the target, these M pulse signals are reflected back and received and processed by the radar receiver. Correspondingly, the echo signal reflected from the target at the m-th pulse position is represented as: (2) in, This represents the echo signal corresponding to the pulse signal with the same carrier frequency at the m-th position, where m takes values ​​from 1 to M. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. Indicates the slant range between the target and the radar. , The radial velocity of the target, The initial distance between the target and the radar is represented by t, which represents the fast time. This represents the slow time of the i-th pulse at the m-th position. Indicates echo delay, 'c' represents the azimuth angle, and 'c' represents the speed of light.

[0029] S30: Perform distance pulse compression processing on the echo signal for each wave position.

[0030] Specifically, a range-to-Fourier transform is performed on the echo signal to transform the signal to the frequency domain; a pulse compression matching function is constructed, and the pulse compression matching function is used to perform frequency domain pulse compression processing on the signal after the range-to-frequency domain transformation.

[0031] For each pulse echo signal at each wavelength, the signal is transformed into the frequency domain by performing a range-to-Fourier transform; then, a pulse compression matching function is constructed, the formula of which in the range-frequency domain is expressed as: (3) in, γ represents the frequency point corresponding to the fast time t, and γ represents the linear frequency modulation slope.

[0032] Using formula (3), the signal after Fourier frequency domain transformation is subjected to pulse compression processing. The signal after pulse compression processing is expressed as follows: (4) in, This represents the range pulse compressed signal corresponding to the selected m-th pulse signal with the same carrier frequency. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. The radial velocity of the target relative to the radar platform. This indicates the initial distance between the target and the radar. Let c represent the slow time of the i-th pulse at the m-th wave position, and c represent the speed of light. This indicates the frequency point corresponding to a fast time t.

[0033] S40: Perform distance travel correction processing on the signal after distance pulse compression.

[0034] A range travel correction filter function is constructed, and the range travel correction filter function is used to perform range travel correction processing on the signal after range pulse compression processing; the range travel correction processed signal is then subjected to range-direction inverse Fourier transform to transform the signal to the time domain.

[0035] Since the targets detected by radar are usually in relative motion, the relative motion between the radar and the target causes differences in the distance of the pulse signal of each wave position. Therefore, the signal after range pulse compression processing needs to be corrected for range travel.

[0036] First, construct the movement correction filter function, expressed by the formula: (5) in Let v represent the slow time of the i-th pulse at the m-th wave position, v be the target velocity provided by the radar inertial navigation system, and c represent the speed of light. This indicates the frequency point corresponding to a fast time t.

[0037] The range pulse compression signal is subjected to range travel correction using formula (5). The range travel corrected signal is expressed in the frequency domain as follows: (6) Then, the signal after range travel correction is subjected to inverse range Fourier transform to transform the signal to the time domain. The signal after inverse range Fourier transform is represented as follows: (7) in, This represents the distance-corrected signal corresponding to the selected m-th pulse signal with the same carrier frequency. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam pointing to the m-th beam, where T represents the pulse width and γ represents the frequency modulation slope. This indicates the initial distance between the target and the radar. Let represent the slow time of the i-th pulse at the m-th wave position, c represent the speed of light, and t represent the fast time.

[0038] S50: Perform initial phase compensation for jitter on the same frequency signal after distance travel correction for each wave position.

[0039] Construct a jitter Doppler phase compensation function, and use the jitter Doppler phase compensation function to perform jitter Doppler phase compensation processing on all pulses after distance movement correction processing; Construct a jitter initial phase compensation filter from the first echo signal after jitter Doppler phase compensation processing of each pulse position. The jitter initial phase compensation filter is used to compensate the jitter initial phase of the second pulse echo signal after the jitter Doppler compensation of the wave position, thereby achieving jitter initial phase compensation for each wave position echo signal.

[0040] Since the carrier frequencies of different wavelengths are completely different, the Doppler phase of different wavelengths is non-uniform, and jitter Doppler phase compensation is required for the signal after distance travel correction.

[0041] First, construct the jitter Doppler phase compensation function, expressed by the formula: (8) in Let be the jitter Doppler phase compensation function for the i-th pulse at the m-th position. Let i be the carrier frequency of the m-th pulse. Let c represent the slow time of the i-th pulse at the m-th wave position, and c represent the speed of light. The radial velocity of the target relative to the radar platform.

[0042] The jitter Doppler phase compensation function is used to perform jitter Doppler phase compensation processing on the signal after range travel correction. The signal after jitter Doppler phase compensation processing is expressed as: (9) Since pulse signals with the same carrier frequency have the same initial phase during jitter, a jitter initial phase compensation filter is constructed from the first echo signal after Doppler phase compensation processing for each pulse jitter. The formula is expressed as: (10) in This represents the carrier frequency of the first pulse at the m-th position. The target scattering coefficient is the first pulse of the m-th wave position. This represents the target antenna amplitude gain of the first pulse at the m-th wave position. This represents the azimuth angle to which the m-th beam is pointing.

[0043] The formula for the second echo signal after jitter Doppler phase compensation processing of the m-th pulse is as follows: (11) in This represents the carrier frequency of the second pulse at the m-th position. The target scattering coefficient is the second pulse of the m-th wave position. This represents the target antenna amplitude gain of the second pulse at the m-th position. This represents the azimuth angle to which the m-th beam is pointing.

[0044] Since the two pulses at each wavelength have the same carrier frequency, this means that the carrier frequency, beam pointing azimuth angle, target scattering coefficient, and antenna amplitude gain of the first and second pulse signals at the m-th wavelength can all be considered the same for a short period of time. , , For the sake of convenience in subsequent image representation, let's assume that... .

[0045] The jitter initial phase compensation filter is used to perform jitter initial phase compensation processing on the second pulse echo signal at the m-th position after jitter Doppler phase compensation processing. The echo signal at the m-th position after jitter initial phase compensation is expressed as: (12) in, This represents the echo signal after initial phase compensation for the jitter of the m-th wave position. Let m be the target scattering coefficient. This represents the target antenna amplitude gain at the m-th position. This represents the azimuth angle of the m-th beam, and t represents the fast time. The slow time of the m-th wave position is represented by γ, the frequency modulation slope is represented by γ, and the pulse width is represented by T. This represents the slant range between the target and the radar at the m-th wave position observation. The initial distance between the target and the radar is represented by , and c represents the speed of light.

[0046] S60: Perform angle super-resolution imaging processing on echo signals of different wave positions after initial phase compensation for jitter.

[0047] Construct an observation matrix of the squared sampled values ​​of the two-way antenna pattern; Based on the probability distributions of the target and noise, the imaging process is transformed into a convex optimization problem of the maximum likelihood function. The target scattering coefficient is estimated by solving the convex optimization problem of the maximum likelihood function using a sparse Bayes-based convex optimization algorithm. The final imaging result is obtained based on the estimated scattering coefficient.

[0048] First, construct the observation matrix of the squared sample values ​​of the two-way antenna pattern, expressed by the formula: (13) Where A represents the squared observation matrix of the two-way antenna pattern samples. This represents the first sampled value of the radar two-way antenna pattern. This represents the Mth sampled value of the radar two-way antenna pattern.

[0049] From formula (12), it can be seen that for this echo signal, in a specific range cell along the azimuth direction, it can be equivalently regarded as the convolution operation of the square of the target scattering coefficient distribution function and the square of the antenna pattern function. Based on this, the echo signal model can be further simplified to: (14) in, This represents the signal echo model after jitter phase compensation. The square of the target scattering coefficient distribution function is given. This represents the square of the antenna pattern function. This represents the convolution operation. This represents the noise function.

[0050] To facilitate mathematical derivation, formula (14) is converted into matrix form: (15) Solving equation (11) using super-resolution deconvolution yields the constraint expression: (16) Analysis of formulas (14) to (16) shows that this embodiment transforms the forward-looking super-resolution imaging problem into a corresponding optimization model, i.e., the problem of estimating the target scattering coefficient based on constraints. Since different imaging scenarios all follow their corresponding probability distributions, a statistical model of the scattering scenario can be constructed accordingly. In this invention, the Laplace probability distribution function is used to establish the statistical model of the scattering scenario, and the noise environment is set to Gaussian noise. Based on this, the probability density function of the target scattering coefficient and the probability density function of the noise can be obtained, resulting in the maximum likelihood function. This is expressed as: (17) in, This indicates the target echo signal after jitter initial phase compensation. The probability density function representing the target scattering coefficients. Let μ represent the probability density of the noise, A represent the standard deviation of the noise, and A represent the matrix representation of the squared antenna pattern function. This indicates the search for the l2-norm.

[0051] By establishing the target echo signal after jitter initial phase compensation The maximum a posteriori probability estimation function is used, and a convex optimization problem of the maximum likelihood function is solved using a sparse Bayes-based convex optimization algorithm to estimate the square of the target scattering coefficient. : (18) in, , Represents the coefficients of the Laplace function. This indicates the search for the l1-norm.

[0052] The optimization problem shown in equation (18) can be solved using a quasi-Newton method (but not limited to this method), through multiple iterations until the preset termination condition is met: (19) in, The square of the target scattering coefficient at the k-th iteration This represents the square of the target scattering coefficient at the (k-1)th iteration. This represents the iteration convergence threshold, which can generally be set to 10. -4 .

[0053] Finally, the optimized result is substituted into formula (12) to obtain the final imaging optimization result.

[0054] To verify the effectiveness of the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation provided in this embodiment of the invention, the following experiments were conducted.

[0055] 1. Experimental simulation parameters The radar parameters involved in the experiment are shown in Table 1. The pulse signals transmitted in a completely random frequency-agile manner are as follows: Figure 2 As shown.

[0056] Table 1 Radar Parameters 2. Experimental Results Figure 3 This is a schematic diagram showing the initial positions of five targets measuring 10 meters by 10 meters. Figure 4 It can be seen that, under the conditions of a scanning beamwidth of 6° and an operating distance of 5000m, the azimuth resolution of conventional forward-looking imaging images with a real aperture is extremely low. Figure 5 and Figure 6 The images are the results of the traditional step-frequency imaging method and the imaging method proposed in this invention, respectively. Due to interference from false targets, compared to... Figure 5 ,from Figure 6 It can be seen that the imaging method proposed in this invention has stronger anti-interference imaging capabilities and can avoid the influence of false target interference.

[0057] In summary, the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation proposed in this invention addresses the vulnerability of forward-looking imaging radars under linear frequency modulation (LFM) and stepped frequency systems to interference. Through a completely random waveform design, a random frequency-agile waveform is applied to forward-looking radar, and an imaging algorithm is provided for receiving echo signals from the completely random frequency-agile waveform: Multiple pulse signals are transmitted in a completely random frequency-agile manner; each wave position contains two pulse signals, with the same carrier frequency for pulse signals at the same wave position and different carrier frequencies for pulse signals at different wave positions; the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position are received; for each wave position's echo signal, the following steps are performed: range pulse compression processing is applied to the echo signal; range travel correction is applied to the range pulse compressed signal; jitter initial phase compensation is applied to the same-frequency signal after range travel correction for each wave position; and angle super-resolution imaging processing is performed on the echo signals from different wave positions after jitter initial phase compensation. Simulation results demonstrate that applying completely random frequency-agile waveforms to forward-looking radar systems can effectively suppress interference signals and achieve super-resolution imaging in azimuth. Furthermore, this invention, by performing jitter initial phase compensation on the range-travel-corrected co-frequency signals of each wave position, eliminates the jitter initial phase effect caused by frequency agility without employing more complex high-bandwidth synthesis algorithms, significantly reducing the processing complexity of frequency-agile waveform forward-looking radar imaging.

[0058] Based on the same concept, the present invention also provides a frequency-agile waveform forward-looking radar imaging system with jitter phase compensation, comprising: The signal transmission module is used to transmit multiple pulse signals in a completely random frequency agile manner; wherein each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; The signal receiving module is used to receive the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; The pulse compression module is used to perform distance pulse compression processing on the echo signal of each wave position; The distance travel correction module is used to perform distance travel correction on the signal after distance pulse compression. The phase compensation module is used to perform jitter phase compensation on the echo signal after distance travel correction; The imaging module is used to perform angular super-resolution imaging processing on echo signals of different wave positions after jitter phase compensation.

[0059] Based on the same concept, the present invention also provides an electronic device, comprising: a memory for storing a processing program; and a processor that, when executing the processing program, implements the frequency agile waveform forward-looking radar imaging method with jitter phase compensation as described above.

[0060] Based on the same concept, the present invention also provides a readable storage medium storing a processing program, which, when executed by a processor, implements the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation as described above.

[0061] If the jitter phase compensation frequency-agile waveform forward-looking radar imaging method is implemented in the form of program instructions and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in software. This computer software is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this disclosure. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0062] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific identification content executed by the system and device described above can be referred to the corresponding process in the foregoing method embodiments.

[0063] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A frequency-agile waveform forward-looking radar imaging method with jitter phase compensation, characterized in that, Includes the following steps: Multiple pulse signals are transmitted in a completely random frequency agile manner; each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; Receive the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; Range pulse compression processing is performed on the echo signal of each wave position; Perform distance travel correction on the signal after distance pulse compression; Perform jitter phase compensation on the echo signal after distance travel correction; Angular super-resolution imaging processing was performed on the echo signals of different wave positions after jitter phase compensation.

2. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, Each transmitted pulse signal is represented as: in, This represents the m-th pulse signal. This represents a rectangular gate function, where T represents the pulse width. t represents the frequency modulation slope, and t represents the fast time. Let i be the carrier frequency of the m-th pulse. This represents the frequency hopping interval of the m-th pulse. The starting frequency point; Each wavelength contains two pulse signals, and the two pulse signals of the same wavelength have the same carrier frequency element.

3. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, The echo signal received from the target at the m-th wave position is represented as: in, This represents the echo signal corresponding to the pulse signal with the same carrier frequency at the m-th position, where m takes values ​​from 1 to M. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam of the m-th beam, T represents the pulse width, and γ represents the frequency modulation slope. Indicates the slant range between the target and the radar. , The radial velocity of the target, The initial distance between the target and the radar is represented by t, which represents the fast time. This represents the slow time of the i-th pulse at the m-th position. Indicates echo delay, 'c' represents the azimuth angle, and 'c' represents the speed of light.

4. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, Range pulse compression processing for the echo signal at each wave position further includes: Perform a distance-to-Fourier transform on the echo signal to transform the signal to the frequency domain; Construct a pulse compression matching function, and use the pulse compression matching function to perform frequency domain pulse compression processing on the signal after range-to-frequency domain transformation; The signal after distance pulse compression processing is: in, This represents the range pulse compressed signal corresponding to the selected m-th pulse signal with the same carrier frequency, where m ranges from 1 to M. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam of the m-th beam, T represents the pulse width, and γ represents the frequency modulation slope. Indicates the slant range between the target and the radar. , The radial velocity of the target relative to the radar platform. The initial distance between the target and the radar is represented by t, which represents the fast time. This represents the slow time of the i-th pulse at the m-th position. Indicates echo delay, 'c' represents the azimuth angle, and 'c' represents the speed of light. This indicates the frequency point corresponding to a fast time t.

5. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, Further range travel correction processing of the signal after range pulse compression includes: Construct a travel correction filter function, and use the travel correction filter function to perform range travel correction processing on the signal after range pulse compression processing; Perform a range-direction inverse Fourier transform on the signal after range travel correction to transform the signal into the time domain; The signal after the inverse Fourier transform of the distance is represented as: in, This represents the distance-corrected signal corresponding to the selected m-th pulse signal with the same carrier frequency. This represents the carrier frequency of the i-th pulse at the m-th position. Let be the target scattering coefficient of the m-th wave position and the i-th pulse. This represents the target antenna amplitude gain for the m-th pulse at the i-th position. This represents the azimuth angle of the i-th pulse beam of the m-th beam, T represents the pulse width, and γ represents the frequency modulation slope. This indicates the initial distance between the target and the radar. Let represent the slow time of the i-th pulse at the m-th wave position, c represent the speed of light, and t represent the fast time.

6. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, Jitter phase compensation is applied to the distance-corrected echo signal, including: Construct a jitter Doppler phase compensation function, and use the jitter Doppler phase compensation function to perform jitter Doppler phase compensation processing on all pulses after distance movement correction processing; Construct a jitter initial phase compensation filter from the first echo signal after jitter Doppler phase compensation processing of each pulse position. The jitter initial phase compensation filter is used to compensate the jitter initial phase of the second pulse echo signal after jitter Doppler compensation processing of the wave position echo signal to achieve jitter initial phase compensation for each wave position echo signal. The echo signal after initial phase compensation for the jitter at the m-th position is represented as: in, This represents the echo signal after initial phase compensation for the jitter of the m-th wave position. Let m be the target scattering coefficient. This represents the target antenna amplitude gain at the m-th position. This represents the azimuth angle of the m-th beam, and t represents the fast time. The slow time of the m-th wave position is represented by γ, the frequency modulation slope is represented by γ, and the pulse width is represented by T. This represents the slant range between the target and the radar at the m-th wave position observation. The initial distance between the target and the radar is represented by , and c represents the speed of light.

7. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, Angular super-resolution imaging processing is performed on echo signals of different wave positions after initial phase compensation for jitter, including: Construct an observation matrix of the squared sampled values ​​of the two-way antenna pattern; Based on the probability distributions of the target and noise, the imaging process is transformed into a convex optimization problem of the maximum likelihood function. The target scattering coefficient is estimated by solving the convex optimization problem of the maximum likelihood function using a sparse Bayes-based convex optimization algorithm. The final imaging result is obtained based on the estimated scattering coefficient.

8. The frequency-agile waveform forward-looking radar imaging method with jitter phase compensation according to claim 1, characterized in that, The observation matrix, which is the square of the sampled values ​​of the two-way antenna pattern, is represented as follows: ； Where A represents the squared observation matrix of the two-way antenna pattern samples. This represents the first sampled value of the radar two-way antenna pattern. This represents the Mth sampled value of the radar two-way antenna pattern.

9. A frequency-agile waveform forward-looking radar imaging system with jitter phase compensation, characterized in that, include: The signal transmission module is used to transmit multiple pulse signals in a completely random frequency agile manner; wherein each wave position contains two pulse signals, the pulse signals in the same wave position have the same carrier frequency, and the pulse signals in different wave positions have different carrier frequencies; The signal receiving module is used to receive the echo signals reflected by each pulse signal after the radar beam illuminates the target at each wave position; The pulse compression module is used to perform distance pulse compression processing on the echo signal of each wave position; The distance travel correction module is used to perform distance travel correction on the signal after distance pulse compression. The phase compensation module is used to perform jitter phase compensation on the echo signal after distance travel correction; The imaging module is used to perform angular super-resolution imaging processing on echo signals of different wave positions after jitter phase compensation.

10. A readable storage medium, characterized in that, The readable storage medium stores a processing program, which, when executed by a processor, implements the frequency-agile waveform forward-looking radar imaging method with jitter phase compensation as described in any one of claims 1 to 8.

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