An improved random frequency hopping radar imaging method, device, equipment and medium

Abstract

This application relates to an improved random frequency hopping radar imaging method, apparatus, computer equipment, and storage medium. The method includes: modulating the original random frequency hopping radar signal with pulse repetition time using a defined sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency; detecting a target using the jointly modulated random frequency hopping signal; compensating the nonlinear phase term of each range cell in the target echo mixing signal using a preset kernel function; performing a Fast Fourier Transform (FFT) on the compensated baseband echo signal of each range cell; and outputting the range image in the Doppler channel with the highest energy as the high-resolution range image of the target. This invention eliminates high-order coupling terms between motion and frequency, utilizes kernel function correlation combined with FFT for fast imaging, avoids the target velocity estimation step in the imaging process, reduces computational load, and is beneficial for engineering implementation.

Description

Technical Field

[0001] This application relates to the field of radar imaging technology, and in particular to an improved random frequency hopping radar imaging method, apparatus, computer equipment, and storage medium based on PRT and frequency joint modulation. Background Technology

[0002] Anti-deception and anti-jamming technology is a core technology in radar detection and identification. The waveform design and coherent processing of radar signals are a key research area in radar system design, largely determining the radar's detection and anti-jamming capabilities. Therefore, designing a reasonable signal waveform is crucial for improving the detection accuracy and anti-jamming capabilities of the radar system.

[0003] In low-interception waveform design, signal systems with anti-jamming capabilities mainly include random frequency-agile systems, random noise systems, and random frequency-hopping systems. Traditional frequency-agile radars do not consider inter-pulse coherent synthesis of high-resolution range images, making it difficult to extract detailed target information. The signal frequency of random noise systems is continuously modulated by noise; the full-band characteristics of the noise make the signal difficult to sample, store, and recover, requiring processing through delay correlation and other methods, which are impractical for real-world applications. Random frequency-hopping signals can be viewed as a discrete form of noise signals; they detect target areas by transmitting a set of randomly varying single-frequency sub-pulses. Compared to noise signal systems, single-frequency signals can be directly stored and synthesized using digital frequencies; simultaneously, random frequency-hopping signals can achieve high-resolution imaging through coherent accumulation. Therefore, random frequency-hopping signals are a low-interception signal waveform with excellent anti-jamming performance.

[0004] When imaging targets using random frequency hopping radar, the high-order phase terms introduced by target motion will cause defocusing of the range image, requiring motion compensation. Zhou L et al. estimated the target velocity using the cross-correlation results of adjacent range images, and their compensation accuracy was comparable to the range resolution, but could not meet the compensation accuracy requirements of the wavelength of the random frequency hopping signal. Li X et al. determined the target velocity by searching for the extremum of the cost function within the range gate, but the algorithm performance was sensitive to the search step size and range. Huang T et al. applied compressed sensing theory to improve random frequency hopping radar imaging, but the construction of the atomic dictionary required traversing all possible velocities and accelerations of the target, and the huge computational load was difficult to meet the requirements of real-time applications. Liao ZK et al. proposed a velocity estimation method based on complementary code modulation, which achieved high-precision velocity estimation by transmitting adjacent pulse trains with complementary relationships. Its disadvantage is that it requires two pulse trains to complete the velocity estimation, reducing the radar data rate. When using the motion compensation approach to achieve high-resolution imaging of random frequency hopping radar, it usually comes at the cost of sacrificing computational load or estimation accuracy. Therefore, existing technologies suffer from problems of high computational load or low accuracy. Summary of the Invention

[0005] Therefore, it is necessary to provide an improved random frequency hopping radar imaging method, apparatus, computer equipment, and storage medium based on PRT and frequency joint modulation that can avoid the target velocity estimation step, in order to address the above-mentioned technical problems.

[0006] An improved random frequency hopping radar imaging method, the method comprising:

[0007] The sub-pulse repetition time modulation formula of the random frequency hopping radar signal is defined based on the preset original random frequency hopping radar signal;

[0008] The original random frequency hopping radar signal is subjected to pulse repetition time modulation according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0009] The target is detected by a random frequency-hopping signal modulated by the pulse repetition time and frequency, and the target echo mixed signal is obtained; the target echo mixed signal includes a nonlinear phase term modulated by the distance to the target scattering center;

[0010] The nonlinear phase term of each range unit in the target echo mixer signal is compensated by a preset kernel function to obtain the baseband echo signal after compensation for each range unit.

[0011] A fast Fourier transform is performed on the baseband echo signal after compensation for each range unit, and the range image in the Doppler channel with the highest energy is output as the target high-resolution range image.

[0012] An improved random frequency hopping radar imaging device, the device comprising:

[0013] The subpulse repetition time modulation formula determination module is used to define the subpulse repetition time modulation formula of the random frequency hopping radar signal based on the preset original random frequency hopping radar signal.

[0014] The pulse repetition time and frequency joint modulation module is used to perform pulse repetition time modulation on the original random frequency hopping radar signal according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0015] The target echo mixing signal acquisition module is used to detect the target by using a random frequency hopping signal jointly modulated by the pulse repetition time and frequency, and obtain the target echo mixing signal; the target echo mixing signal includes a nonlinear phase term modulated by the distance to the target scattering center;

[0016] The nonlinear phase term compensation module is used to compensate the nonlinear phase term of each range unit in the target echo mixing signal using a preset kernel function, so as to obtain the baseband echo signal after compensation for each range unit.

[0017] The imaging output module is used to perform a fast Fourier transform on the baseband echo signal after compensation for each range unit, and output the range image in the Doppler channel with the highest energy as the target high-resolution range image.

[0018] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program performing the following steps:

[0019] The sub-pulse repetition time modulation formula of the random frequency hopping radar signal is defined based on the preset original random frequency hopping radar signal;

[0020] The original random frequency hopping radar signal is subjected to pulse repetition time modulation according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0021] The target is detected by a random frequency-hopping signal modulated by the pulse repetition time and frequency, and the target echo mixed signal is obtained; the target echo mixed signal includes a nonlinear phase term modulated by the distance to the target scattering center;

[0022] The nonlinear phase term of each range unit in the target echo mixer signal is compensated by a preset kernel function to obtain the baseband echo signal after compensation for each range unit.

[0023] A fast Fourier transform is performed on the baseband echo signal after compensation for each range unit, and the range image in the Doppler channel with the highest energy is output as the target high-resolution range image.

[0024] A computer-readable storage medium having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0025] The sub-pulse repetition time modulation formula of the random frequency hopping radar signal is defined based on the preset original random frequency hopping radar signal;

[0026] The original random frequency hopping radar signal is subjected to pulse repetition time modulation according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0027] The target is detected by a random frequency-hopping signal modulated by the pulse repetition time and frequency, and the target echo mixed signal is obtained; the target echo mixed signal includes a nonlinear phase term modulated by the distance to the target scattering center;

[0028] The nonlinear phase term of each range unit in the target echo mixer signal is compensated by a preset kernel function to obtain the baseband echo signal after compensation for each range unit.

[0029] A fast Fourier transform is performed on the baseband echo signal after compensation for each range unit, and the range image in the Doppler channel with the highest energy is output as the target high-resolution range image.

[0030] The aforementioned improved random frequency hopping radar imaging method, apparatus, computer equipment, and storage medium modulate the original random frequency hopping radar signal using a defined sub-pulse repetition time modulation formula, obtaining a random frequency hopping signal jointly modulated by pulse repetition time and frequency. This signal is then used to detect the target, yielding a target echo mixing signal. A preset kernel function compensates for the nonlinear phase term of each range cell in the target echo mixing signal. A Fast Fourier Transform (FFT) is then performed on the compensated baseband echo signal for each range cell, and the range image in the Doppler channel with the highest energy is output as the high-resolution range image of the target. This invention, based on the conventional random frequency hopping waveform, eliminates high-order coupling terms between motion and frequency by changing the pulse repetition period. Furthermore, it utilizes the kernel function correlation method combined with FFT for fast imaging. This avoids the target velocity estimation step during the imaging process, reducing computational load and facilitating engineering implementation. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating an improved random frequency hopping radar imaging method in one embodiment;

[0032] Figure 2 This is a schematic diagram of the original random frequency hopping radar waveform in one embodiment;

[0033] Figure 3 This is a schematic diagram of a random frequency hopping radar waveform jointly modulated by PRT and frequency in one embodiment.

[0034] Figure 4 This is a flowchart of a random frequency hopping signal imaging process using pulse repetition time and frequency joint modulation in one embodiment.

[0035] Figure 5 This is a schematic diagram comparing the pulse transmission times of a random frequency hopping signal modulated by the pulse repetition time and frequency in one embodiment with those of the original random frequency hopping waveform.

[0036] Figure 6The following are imaging results under different control errors in one embodiment: (a) is the imaging result with a control error of 10 μs, (b) is the imaging result with a control error of 20 μs, (c) is the imaging result with a control error of 50 μs, and (d) is the imaging result with a control error of 100 μs.

[0037] Figure 7 Here is a distance occlusion analysis diagram in one embodiment, where (a) is the PRT of the new waveform, and (b) is a diagram showing the relationship between the number of occlusions and the detection distance.

[0038] Figure 8 The following is a comparison of distance occlusion and imaging results in one embodiment: (a) shows the subpulse occlusion at 4.5 km, (b) shows the high-resolution distance imaging result at 4.5 km, (c) shows the subpulse occlusion at 6 km, (d) shows the high-resolution distance imaging result at 6 km, (e) shows the subpulse occlusion at 7.5 km, and (f) shows the high-resolution distance imaging result at 7.5 km.

[0039] Figure 9 Here is a comparison of high-resolution distance imaging results in a specific embodiment, where (a) is the imaging result with an adjustment error of 10 μs, (b) is the imaging result with an adjustment error of 20 μs, (c) is the imaging result with an adjustment error of 50 μs, and (d) is the imaging result with an adjustment error of 100 μs.

[0040] Figure 10 The following is a comparison of the imaging results of measured data in a specific embodiment, wherein (a) is the original range image imaging result, (b) is the range image imaging result at a velocity of 5 m / s, (c) is the range image imaging result at a velocity of 5 m / s, and (d) is the range image imaging result at a velocity of 5 m / s.

[0041] Figure 11 This is a structural block diagram of an improved random frequency hopping radar imaging device in one embodiment;

[0042] Figure 12 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] Random frequency hopping (RF-HQ) is a high-performance signal waveform with strong anti-interference capabilities and low probability of interception. However, traditional RF-HQ signals are sensitive to target motion, and the coupling between target motion and frequency modulation introduces higher-order phase terms into the echo, causing range image defocusing. This invention proposes an improved RF-HQ radar imaging method based on PRT and frequency joint modulation.

[0045] In one embodiment, such as Figure 1 As shown, an improved random frequency hopping radar imaging method is provided, including the following steps:

[0046] Step 102: Define the subpulse repetition time modulation formula of the random frequency hopping radar signal based on the preset original random frequency hopping radar signal.

[0047] like Figure 2 As shown, random frequency hopping radar obtains high-resolution range images by processing a set of coherent pulse trains with randomly arranged frequencies. Each pulse train contains... A single-frequency sub-pulse, with a pulse width of... The pulse repetition period is Assume the bandwidth of the random frequency hopping radar is... The minimum frequency hopping step size is Then the number of sub-pulses satisfies Random frequency hopping radar signals can be represented as follows:

[0048] (1)

[0049] in, For signal carrier frequency, The frequency hopping coefficient represents the frequency hopping factor. this After randomly arranging the n integers, the nth... The value of the number, corresponding to the first The frequency of each sub-pulse is . The unit rectangle function is expressed as follows:

[0050] (2)

[0051] Assuming the target includes The scattering center, the th scattering center The intensity of each scattering center is , No. The sub-pulse emission time is the The distance between each scattering center and the radar is ,but The change with launch time can be expressed as:

[0052] (3)

[0053] in Indicates the initial time. The distance between each scattering center and the radar. This represents the projected component of the target velocity along the radar line of sight.

[0054] The target echo after mixing can be expressed as

[0055] (4)

[0056] In the phase term of the above equation, the first term is a constant and has no effect on imaging; the second term is the random nonlinear phase delay introduced by the distance between each scattering center, which is the information required for high-resolution imaging; the third term is an additional phase term introduced by target motion, including both linear phase terms introduced by motion and higher-order coupling terms between frequency random modulation and target motion, which will cause defocusing of the range image. When synthesizing high-resolution range images, existing methods typically... An estimate is made, and then a compensation factor is constructed to eliminate the influence of the motion additional term. The estimation requires a large amount of computing resources and is subject to estimation errors.

[0057] The random frequency hopping signal jointly modulated by the pulse repetition time (PRT) and frequency proposed in this invention is as follows: Figure 3 As shown, except for PRT, the signal parameters of each pulse train are consistent with those of a traditional random frequency hopping signal. The repetition time of each sub-pulse is determined by the following formula:

[0058] (5)

[0059] in This is the pulse repetition time parameter, and its magnitude is consistent with the pulse repetition time of a conventional random frequency hopping signal.

[0060] Step 104: Modulate the original random frequency hopping radar signal with pulse repetition time according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0061] Substituting equation (5) into equation (3) yields

[0062] (6)

[0063] Step 106: The target is detected by a random frequency hopping signal modulated by the pulse repetition time and frequency, and the target echo mixing signal is obtained.

[0064] The target echo after mixing can be expressed as

[0065] (7)

[0066] By comparing equation (4), it can be seen that the higher-order phase terms coupled with the target motion of the frequency nonlinear modulation have been eliminated. However, the echo phase consists of a random nonlinear phase introduced by the distance to the scattering center and a linear phase introduced by the velocity. The superposition of the linear and nonlinear phases means that neither FFT nor kernel function methods can directly achieve high-resolution imaging.

[0067] Step 108: Compensate the nonlinear phase term of each range unit in the target echo mixing signal using a preset kernel function to obtain the compensated baseband echo signal for each range unit.

[0068] Although PRT combined with frequency modulation eliminates the motion-inducing higher-order phase terms, the nonlinear phase of the scattering center distance modulation and the linear phase of the motion modulation are still superimposed in the echo, making direct high-resolution imaging difficult. This invention employs a combination of kernel function compensation and FFT to achieve high-resolution range imaging. For each range cell, the random nonlinear phase term is compensated using a kernel function to obtain the corresponding linear phase echo. Then, FFT is used to focus the linear phase signal. The specific process is as follows:

[0069] Assume the distance resolution of the randomly frequency-hopping signal is The number of range units contained within the imaging range gate is For each sub-pulse, the first The kernel function for each distance cell is set as follows:

[0070] (8)

[0071] in, Count the sub-pulses. Utilize the echoes of each sub-pulse. The baseband echo after compensation for each range cell is calculated separately. The compensation process is as follows:

[0072] (9)

[0073] in For constant phase terms, when the first term... The scattering center exists in the first... When there are distance units, there are Substituting into equation (9), we get:

[0074] (10)

[0075] It can be seen that after compensation, the first The echo from each scattering center is manifested as The phase linear transformation sequence.

[0076] Step 110: Perform a fast Fourier transform on the baseband echo signal after compensation for each range cell, and output the range image in the Doppler channel with the highest energy as the target high-resolution range image.

[0077] After compensation The echo from each scattering center is manifested as The phase linear transform sequence, after FFT, will coherently accumulate the echo energy in the first phase linear transform sequence. The number of Doppler units is [number]; meanwhile, the nonlinear phase modulation of other scattering center components still exists, resulting in a defocused state after FFT. Therefore, by performing FFT on the echo sequence of each range unit separately, the [echo sequence] can be obtained at the [number]th [range unit]. The coherent accumulation results of the distance cell are obtained from each Doppler cell.

[0078] (11)

[0079] In practical applications, the target velocity is unknown. Assuming the target velocity remains approximately constant within one pulse train imaging time, the energy of all scattering centers on the target is shifted to the [missing information - likely a specific point in time]. Therefore, we output the range image from the Doppler channel with the highest energy as the high-resolution range image of the target. The imaging flowchart is as follows: Figure 4 As shown.

[0080] In the aforementioned improved random frequency hopping radar imaging method, the original random frequency hopping radar signal is modulated by pulse repetition time using a defined sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency. The target is then detected using this jointly modulated random frequency hopping signal to obtain a target echo mixing signal. A preset kernel function is used to compensate for the nonlinear phase term of each range cell in the target echo mixing signal. A Fast Fourier Transform (FFT) is then performed on the compensated baseband echo signal for each range cell, and the range image in the Doppler channel with the highest energy is output as the high-resolution range image of the target. This invention, based on the conventional random frequency hopping waveform, eliminates the high-order coupling term between motion and frequency by changing the pulse repetition period. Furthermore, it utilizes the kernel function correlation method combined with FFT for fast imaging. This avoids the target velocity estimation step in the imaging process, reduces computational load, and facilitates engineering implementation.

[0081] In one embodiment, the time control accuracy of the method proposed in this invention is analyzed. Figure 5 A comparison of the pulse repetition time in this embodiment with that of a conventional random frequency hopping signal pulse repetition time is given. Equation (5) shows that the designed PRT is precisely determined by the sub-pulse modulation frequency. However, in practical applications, radar systems typically regulate the PRT based on the operating frequency of the crystal oscillator reference source, and the regulation accuracy is constrained. It is assumed that the maximum regulation error of the radar hardware on the pulse repetition time is... The control error will affect the target's distance at the moment of pulse emission. Equation (6) is modified as follows:

[0082] (12)

[0083] Substituting into equation (7), we get:

[0084] (13)

[0085] in The phase term is introduced to control the error. To achieve coherent accumulation of sub-pulses, the phase error is typically required to be less than [a certain value]. That is, the following inequality must be satisfied:

[0086] (14)

[0087] Assuming the target's maximum speed is Then the above formula can be simplified to:

[0088] (15)

[0089] When the radar carrier frequency is , , At that time, it is necessary to meet the following requirements. Assume the target contains 4 scattering centers with relative distances of [0m, 4.5m, 7.8m, 11m] and scattering intensities of [1, 1, 1, 1] respectively. Figure 6 The time control error of the radar system is given as follows: , , ,as well as High-resolution range imaging results at that time. (From...) Figure 6 It can be seen that when the control error is less than When the high-resolution distance image is focused, it can be effectively focused; however, when the control error reaches... At that time, the additional phase term introduced by the time control error will cause defocusing of the high-resolution range image. This is consistent with the analysis results of equation (15). It should be noted that in practical applications, the time control accuracy of the radar system can reach... Even higher. Therefore, the time control accuracy of the existing system can meet the waveform design requirements of this invention.

[0090] In one embodiment, range blocking analysis is performed on the method proposed in this invention. Compared with conventional random frequency hopping signals, the PRT of the new waveform is constantly changing, which causes the maximum detection range of the sub-pulse to change over time. If the target echo delay is greater than the current pulse repetition period, the radar receiver cannot sample the echo, resulting in range blocking. Therefore, it is necessary to analyze the detection range of the new waveform. Assume... The number of sub-pulses is , A new set of PRT waveforms is randomly generated, such as Figure 7 As shown in (a), compared to the conventional random frequency hopping signal system, the PRT of different sub-pulses changes continuously. Therefore, as the detection distance increases, the number of sub-pulses blocked gradually increases. 10,000 sets of random frequency hopping signal waveforms were randomly generated, and then the average number of sub-pulse blocks corresponding to different detection distances was calculated. The results are shown below. Figure 7 As shown in (b), when the detection distance is 4.5 km, the proportion of blocked sub-pulses is 5%; when the detection distance is 6.5 km, the proportion of blocked sub-pulses is 21%; and when the detection distance is 7 km, the proportion of blocked sub-pulses is approximately 31%. However, conventional random frequency hopping signals do not exhibit distance-based blocking within a detection distance of 7.5 km. Therefore, further analysis of the detection distance for the new waveform is necessary.

[0091] Assume the target contains 4 scattering centers with relative distances of [0m, 4.5m, 7.8m, 11m] and scattering intensities of [1, 1, 1, 1]. The target is stationary, and the radar signal parameters are the same as above. Figure 8 The sub-pulse occlusion of the new waveform at target detection distances of 4.5km, 6km, and 7km are presented, along with the high-resolution range imaging results using the new waveform. For ease of comparison, the high-resolution imaging results of the conventional random frequency hopping waveform are also shown in the figures. As can be seen from the figures, at a detection distance of 4.5km, the number of occluded sub-pulses is 6. When performing high-resolution range imaging on the new waveform, the target scattering center can be effectively focused. However, due to the influence of the missing echoes of the 6 sub-pulses, the range image amplitude of the new waveform is slightly lower than that of the traditional random frequency hopping signal. When the detection distance increases to 6km, the number of occluded sub-pulses increases to 23, at which point the high-resolution range image amplitude decreases by approximately 25%. When the detection distance increases to 7.5km, the number of occluded sub-pulses increases to 64, at which point the high-resolution range image amplitude decreases significantly, making target detection difficult. Therefore, the effective detection range of the new waveform is 6km, which is 80% of the effective detection range of the traditional random frequency hopping signal.

[0092] In one embodiment, a computational complexity analysis is performed on the method proposed in this invention. The high-resolution distance imaging process for the new waveform is as follows: Figure 4 As shown, the computational complexity of imaging mainly consists of kernel-based correlation and FFT transform. The number of high-resolution range cells is typically related to the number of sampling frequency points. Consistent. Each frequency point requires kernel function compensation. Complex number multiplication The total computational cost of kernel function compensation for each frequency point is This involves multiple complex multiplications. Furthermore, the FFT transform needs to be performed once for each distance cell, requiring a computational cost of [number missing]. Multiplication of complex numbers and Complex number addition. Therefore, the total computational cost of the FFT transformation steps is... Multiplication of complex numbers and Complex number addition.

[0093] Conventional random frequency hopping designs, based on known computational costs, further involve adding higher-order phase coupling terms. Compensation estimation is performed, and the minimum waveform entropy velocity estimation method is used as an example to compare computational complexity. Assume the number of velocity sampling points to be searched is... For each velocity sampling point, it is necessary to Complex multiplication is used to compensate for echoes at all frequencies, and then a kernel function method is used for imaging. Each imaging operation requires... Multiplication of complex numbers and The complex number addition is performed several times, followed by the calculation of the entropy value of the distance image. Each calculation requires a computational cost of... Multiplication of complex numbers and This involves multiple complex number additions, therefore the total computational cost is... Multiplication of complex numbers and Complex number addition. The computational complexity of the two methods is summarized in the table below. It can be seen that using the new waveform detection avoids the computational complexity introduced by velocity estimation, thus achieving high computational efficiency.

[0094] Table 1 Comparison of imaging computational costs for different methods

[0095]

[0096] In one specific embodiment, the method proposed in this invention is verified by simulation data imaging. Assuming 128 sub-pulses and a bandwidth of 256MHz, the minimum frequency hopping step size is obtained. Radar carrier frequency 35GHz, pulse repetition time parameters The target contains four scattering centers with relative distances of [0m, 4.5m, 7.8m, 11m] and scattering intensities of [1, 1, 1, 1].

[0097] The target is 3km from the radar, at which range obstruction is negligible. High-resolution range imaging was performed using the new waveform and the traditional random frequency-hopping waveform at target velocities of 0m / s, 5m / s, 10m / s, and 15m / s, respectively. The results are as follows. Figure 9 As shown. By Figure 9As can be seen, when using the traditional random frequency hopping waveform, the high-resolution range image is very sensitive to velocity, and the range image is severely defocused when the target moves. However, when using the waveform designed in this invention, the higher-order phase terms introduced by the target velocity are eliminated, resulting in good range image focusing performance. Simulation results verify the effectiveness of the waveform designed in this invention.

[0098] In one specific embodiment, the method proposed in this invention is verified by imaging with measured data. An ideal scattering point model is applicable when the target is in the optical region; however, it cannot fully reflect the electromagnetic scattering mechanism of complex targets. This section uses measured data to verify the effectiveness of the method. Since there is currently no measured data for the radar signal designed in this invention, the measured data needs to be transformed. The process is as follows: First, the measured linear frequency modulated signal is demodulated to obtain the target range image sequence. Then, it is transformed back to the original data domain through inverse Fourier transform, and then based on the frequency hopping coefficient... The echo data of the random frequency-hopping signal is obtained by rearranging the signals. Assume the target's velocity is... Time parameters The radar carrier frequency is 35GHz, and the bandwidth is 300MHz. One frame of the pulse train contains 256 sub-pulses. The echo phase delay term of each sub-pulse can be calculated by equation (6). Multiplying the frequency data of each sub-pulse by the corresponding phase delay term can convert it into the echo data of the designed waveform.

[0099] Assuming the pulse period of a conventional random frequency hopping signal is , Figure 10 Figures (b), (c), and (d) present the range profile imaging results using conventional random frequency hopping signals and the proposed signal at target velocities of 5 m / s, 10 m / s, and 15 m / s, respectively. As shown in the figures, target motion causes severe defocusing in the range profile synthesized from the random frequency hopping signal, failing to reflect the radial distribution of the target scattering points. In contrast, the proposed signal, free from higher-order interference, does not exhibit defocusing in its range profile. The imaging results from measured data further validate the effectiveness of the proposed method.

[0100] It should be understood that, although Figure 1 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0101] In one embodiment, such as Figure 11 As shown, an improved random frequency hopping radar imaging device is provided, comprising: a sub-pulse repetition time modulation formula determination module 1102, a pulse repetition time and frequency joint modulation module 1104, a target echo mixing signal acquisition module 1106, a nonlinear phase term compensation module 1108, and an imaging output module 1110, wherein:

[0102] The subpulse repetition time modulation formula determination module 1102 is used to define the subpulse repetition time modulation formula of the random frequency hopping radar signal according to the preset original random frequency hopping radar signal.

[0103] The pulse repetition time and frequency joint modulation module 1104 is used to perform pulse repetition time modulation on the original random frequency hopping radar signal according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency.

[0104] The target echo mixing signal acquisition module 1106 is used to detect the target by using a random frequency hopping signal jointly modulated by the pulse repetition time and frequency, and to obtain the target echo mixing signal; the target echo mixing signal includes a nonlinear phase term modulated by the distance of the target scattering center;

[0105] The nonlinear phase term compensation module 1108 is used to compensate the nonlinear phase term of each range unit in the target echo mixing signal through a preset kernel function, so as to obtain the baseband echo signal after compensation for each range unit.

[0106] The imaging output module 1110 is used to perform a fast Fourier transform on the baseband echo signal after compensation for each range cell, and output the range image in the Doppler channel with the highest energy as the target high-resolution range image.

[0107] The sub-pulse repetition time modulation formula determination module 1102 is also used to obtain the preset original random frequency hopping radar signal;

[0108] The subpulse repetition time modulation formula for random frequency hopping radar signals is defined as follows:

[0109]

[0110] in, Indicates the first Sub-pulse, The carrier frequency of the original random frequency hopping radar signal. The frequency hopping coefficients of the original random frequency hopping radar signal are given. The pulse repetition time of the original random frequency hopping radar signal. This represents the minimum frequency hopping step size of the original random frequency hopping radar signal.

[0111] The target echo mixing signal acquisition module 1106 is also used to detect the target by using a random frequency hopping signal jointly modulated by the pulse repetition time and frequency, and obtain the target echo mixing signal as follows:

[0112]

[0113] in, Indicates that the target contains The scattering center, the th scattering center The intensity of each scattering center is , Indicates the initial time. The distance between each scattering center and the radar. This represents the projection component of the target velocity along the radar line of sight. Represents the speed of light. It is the symbol for imaginary numbers. This represents an exponential function.

[0114] The nonlinear phase term compensation module 1108 is also used to compensate for the nonlinear phase term of each range unit in the target echo mixing signal using a preset kernel function; wherein, the first nonlinear phase term of each sub-pulse... The kernel function corresponding to each distance cell is:

[0115]

[0116] in, This represents the distance resolution of the random frequency hopping signal. , This represents the number of range units contained within the imaging range gate.

[0117] The nonlinear phase term compensation module 1108 is also used to compensate for the nonlinear phase term of each range unit in the target echo mixer signal using a preset kernel function:

[0118]

[0119] in, For constant phase terms, when the first term... The scattering center exists in the first... When there are distance units, there are The baseband echo signal after compensation for each range cell is obtained as follows:

[0120] .

[0121] The imaging output module 1110 is also used to perform a fast Fourier transform on the baseband echo signal after compensation for each range cell:

[0122]

[0123] in, Indicates Fast Fourier Transform;

[0124] The range image from the Doppler channel with the highest energy is output as the high-resolution range image of the target; the Doppler channel with the highest energy is the [number missing]. One Doppler channel.

[0125] Specific limitations regarding the improved random frequency hopping radar imaging device can be found in the limitations of the improved random frequency hopping radar imaging method above, and will not be repeated here. Each module in the aforementioned improved random frequency hopping radar imaging device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0126] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 12 As shown, the computer device includes a processor, memory, network interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements an improved random frequency hopping radar imaging method. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0127] Those skilled in the art will understand that Figure 12 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0128] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the method embodiments described above. A computer-readable storage medium is also provided, on which a computer program is stored, and which, when executed by a processor, implements the steps in the method embodiments described above.

[0129] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An improved random frequency hopping radar imaging method, characterized in that, The method includes: The sub-pulse repetition time modulation formula of the random frequency hopping radar signal is defined based on the preset original random frequency hopping radar signal; The original random frequency hopping radar signal is subjected to pulse repetition time modulation according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency. The target is detected by a random frequency-hopping signal modulated by the pulse repetition time and frequency, and the target echo mixed signal is obtained; the target echo mixed signal includes a nonlinear phase term modulated by the distance to the target scattering center; The nonlinear phase term of each range unit in the target echo mixer signal is compensated by a preset kernel function to obtain the baseband echo signal after compensation for each range unit. A fast Fourier transform is performed on the baseband echo signal after compensation for each range unit, and the range image in the Doppler channel with the highest energy is output as the target high-resolution range image. The step of defining the sub-pulse repetition time modulation formula of the random frequency hopping radar signal based on the preset original random frequency hopping radar signal includes: Acquire the preset raw random frequency hopping radar signal; The subpulse repetition time modulation formula for random frequency hopping radar signals is defined as follows: in, Indicates the first Sub-pulse, The carrier frequency of the original random frequency hopping radar signal is... The frequency hopping coefficients of the original random frequency hopping radar signal are given. The pulse repetition time of the original random frequency hopping radar signal. The minimum frequency hopping step size is the original random frequency hopping radar signal.

2. The method according to claim 1, characterized in that, The target is detected by a random frequency-hopping signal modulated by the pulse repetition time and frequency, resulting in a target echo mixing signal, including: The target echo mixing signal is obtained by detecting the target using a random frequency hopping signal modulated by the pulse repetition time and frequency. in, Indicates that the target contains The scattering center, the th scattering center The intensity of each scattering center is , Indicates the initial time. The distance between each scattering center and the radar. This represents the projection component of the target velocity along the radar line of sight. Represents the speed of light. It is the symbol for imaginary numbers. This represents an exponential function.

3. The method according to claim 2, characterized in that, The nonlinear phase term of each range unit in the target echo mixer signal is compensated using a preset kernel function, including: The nonlinear phase term of each range unit in the target echo mixer signal is compensated using a preset kernel function; wherein, the first... The kernel function corresponding to each distance cell is: in, This represents the distance resolution of the random frequency hopping signal. , This represents the number of range units contained within the imaging range gate.

4. The method according to claim 3, characterized in that, The nonlinear phase term of each range unit in the target echo mixer signal is compensated by a preset kernel function to obtain the compensated baseband echo signal for each range unit, including: The nonlinear phase term of each range unit in the target echo mixer signal is compensated using a preset kernel function: in, For constant phase terms, when the first term... The scattering center exists in the first... When there are distance units, there are The baseband echo signal after compensation for each range cell is obtained as follows: 。 5. The method according to claim 4, characterized in that, Perform a Fast Fourier Transform on the baseband echo signal after compensation for each range unit, and output the range image in the Doppler channel with the highest energy as the target high-resolution range image, including: Perform a Fast Fourier Transform on the baseband echo signal after compensation for each range unit: in, Indicates Fast Fourier Transform; The range image in the Doppler channel with the highest energy is output as the high-resolution range image of the target; the Doppler channel with the highest energy is the [missing information]. One Doppler channel.

6. The method according to any one of claims 1 to 5, characterized in that, The modulation of the pulse repetition time is achieved based on the operating frequency of the crystal oscillator reference source of the radar system.

7. An improved random frequency hopping radar imaging device, characterized in that, The apparatus comprising the method according to any one of claims 1 to 6, wherein the apparatus includes: The subpulse repetition time modulation formula determination module is used to define the subpulse repetition time modulation formula of the random frequency hopping radar signal based on the preset original random frequency hopping radar signal. The pulse repetition time and frequency joint modulation module is used to perform pulse repetition time modulation on the original random frequency hopping radar signal according to the sub-pulse repetition time modulation formula to obtain a random frequency hopping signal jointly modulated by pulse repetition time and frequency. The target echo mixing signal acquisition module is used to detect the target by using a random frequency hopping signal jointly modulated by the pulse repetition time and frequency, and obtain the target echo mixing signal; the target echo mixing signal includes a nonlinear phase term modulated by the distance to the target scattering center; The nonlinear phase term compensation module is used to compensate the nonlinear phase term of each range unit in the target echo mixing signal using a preset kernel function, so as to obtain the baseband echo signal after compensation for each range unit. The imaging output module is used to perform a fast Fourier transform on the baseband echo signal after compensation for each range unit, and output the range image in the Doppler channel with the highest energy as the target high-resolution range image.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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