A broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios

Abstract

The present invention relates to a broadband amplitude and phase distortion compensation scheme adapted to low signal-to-noise ratio scenarios, comprising: obtaining baseband original echoes; i (t) Perform Fourier transform to obtain the original echo one-dimensional range image F i (f); for F i (f) Perform a circular left shift operation on point K to obtain G i (f); Construct frequency domain rectangular window function H i (f), get J i (f) = G i (f)H i (f); for J i (f) Perform inverse Fourier transform to obtain the windowed original echo j i (t); Get j respectively i The normalized amplitude A of (t) i (t) and the phase #imgabs0# are averaged; a broadband amplitude-phase distortion compensation coefficient C(t) is calculated; and the broadband amplitude-phase distortion compensation coefficient C(t) is directly multiplied by the broadband original echo D(t) detected by the radar from a target. The broadband amplitude-phase compensation method adapted to low signal-to-noise ratio scenarios provided by the present invention addresses the problem of poor amplitude-phase distortion compensation effectiveness of traditional methods under low signal-to-noise ratio conditions.

Description

Technical Field

[0001] The present invention relates to the field of signal processing technology, and in particular to a broadband amplitude-phase compensation method adapted to low signal-to-noise ratio scenarios. Background Art

[0002] Limited by the technological limitations of existing components, wideband radars exhibit nonlinear responses in signal generation and the transceiver link. This causes amplitude and phase distortion in the wideband echo signal, which in turn degrades the main-to-sidelobe ratio of the wideband radar's High-Resolution Range Profile (HRRP), leading to poor imaging quality. To ensure the high-resolution performance of wideband radars, a common approach is to utilize single-pulse or multi-pulse accumulation of spherical satellite wideband echoes to extract the system's wideband amplitude and phase distortion compensation coefficients. This effectively compensates for the wideband radar's amplitude and phase distortion, ultimately improving its HRRP main-to-sidelobe ratio.

[0003] However, for some less powerful broadband radars, the signal-to-noise ratio (SNR) of a single pulse broadband echo scattered from a spherical satellite is too weak because the RCS of the spherical satellite is usually small and the distance from the radar is usually far. As a result, (1) it is difficult to extract high-quality broadband amplitude-phase distortion compensation coefficients from a single low-SNR broadband echo; (2) on the other hand, the low SNR makes it impossible to accurately calibrate the phase deviation between multiple broadband pulses, which makes it difficult to obtain high-quality broadband amplitude-phase distortion compensation coefficients through multi-pulse coherent accumulation. In summary, it is usually difficult to effectively compensate for broadband radar amplitude-phase distortion using traditional methods in low SNR scenarios, which results in the inability to effectively improve the HRRP main-sidelobe ratio.

[0004] Related references:

[0005] [1] JV Eshbaugh, RL Morrison, EW Hoen, TC Hiett, and GR Benitz, "HUSIR signal processing," Lincoln Laboratory Journal, vol. 21, no. 1, pp. 115-134, 2014.

[0006] [2] Wang G, Xu R, Cao Z., "System compensation for inverse synthetic aperture radar", Aerospace&Electronics Conference. IEEE, 1994.

[0007] [3] Zhang Peng, Peng Xiliang, Lu Yingying. Experimental research on millimeter-wave high-resolution imaging phased array radar. Modern Radar, 2021, 43(07): 27-31.

[0008] [4] Zhang Rui, Ke Changhai, Gao Aiming. Amplitude and phase distortion compensation method for wideband large aperture radar. Modern Radar, 2021, 43(05): 38-43.

[0009] [5] Yang Wenjun, Xu Yong, Wang Feng, Xiang Yongqi. Extraction method of distortion compensation signal for broadband radar system. Modern Radar, 2006(05):8-11. Summary of the Invention

[0010] To solve the existing technical problems, the present invention provides a broadband amplitude-phase compensation method adapted to low signal-to-noise ratio scenarios.

[0011] The specific content of the present invention is as follows: A broadband amplitude-phase compensation method adapted to low signal-to-noise ratio scenes comprises the following steps:

[0012] Step 1: First, N broadband pulses are transmitted to the spherical satellite. After receiving N broadband echo signals, they are processed by de-skewing, frequency conversion, sampling, and velocity compensation to obtain the de-skewing baseband original echo s i (t) (hereinafter referred to as the original echo), where i = 1, 2, ..., N;

[0013] Step 2: i (t) Perform Fourier transform to obtain the original echo one-dimensional range image F i (f), where F i The center frequency of (f) is f0;

[0014] Step 3: Assuming the system sampling rate is PF and the number of sampling points is M, then i (f) Perform a circular left shift operation on K points to obtain G i (f), where K is the closest integer;

[0015] Step 4: G i The spectrum of (f) shows that the effective signal area is f 1i to f 2i , then construct the frequency domain rectangular window function H i (f):

[0016] ,

[0017] Combine the rectangular window function with G i Multiply (f) and we get ;

[0018] Step 5: Ji (f) Perform inverse Fourier transform to obtain the windowed original echo j i (t), based on the above processing, the noise of the original echo is reduced, j i The signal-to-noise ratio of (t) relative to s i The signal-to-noise ratio of (t) will be improved to a certain extent;

[0019] Step 6: Get j i The normalized amplitude A of (t) i (t) and phase φ i (t):

[0020] ,

[0021] ,

[0022] Among them, max[|j i (t)|] is|j i (t)|, Im[j i (t)] is j i The imaginary part of (t), Re[j i (t)] is j i the real part of (t);

[0023] Step 7: Normalize N amplitudes A i (t) and phase φ i (t) are averaged respectively, thereby effectively reducing the amplitude distortion random error and phase distortion random error, and then extracting the high-precision amplitude distortion A c and phase distortion φ c :

[0024] ,

[0025] ,

[0026] Step 8. Further, the system's high-precision broadband amplitude and phase distortion compensation coefficient C(t) can be expressed as

[0027] ;

[0028] Step 9. Assuming that the broadband original echo detected by the radar for a certain target is D(t), by directly multiplying it with the broadband amplitude and phase distortion compensation coefficient C(t), the amplitude and phase errors of the broadband original echo from the target can be effectively compensated, thereby significantly improving the main-to-sidelobe ratio of the broadband radar HRRP.

[0029] The broadband amplitude-phase compensation method adapted to low signal-to-noise ratio scenarios provided by the present invention solves the problem that the traditional method has poor compensation effect of amplitude-phase distortion under low signal-to-noise ratio conditions. The present invention can accurately extract the system amplitude-phase distortion under low signal-to-noise ratio conditions through measures such as frequency domain windowing noise reduction, time domain amplitude-phase separation and reduction of random errors, thereby achieving effective compensation for the amplitude-phase error of the broadband original echo from the target, and effectively improving the HRRP main-sidelobe ratio of the target. Since the present invention effectively utilizes multiple groups of broadband echo information of spherical satellites and does not require multi-pulse coherent accumulation of the broadband echoes of spherical satellites, it solves the problem that the traditional method is difficult to accurately obtain broadband amplitude-phase distortion parameters under low signal-to-noise ratio conditions, which leads to the inability to effectively improve the main-sidelobe ratio of HRRP of broadband radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specific embodiments of the present invention will be further explained below with reference to the accompanying drawings.

[0031] Figure 1 The following are the implementation steps of the broadband amplitude and phase distortion compensation method proposed by the present invention for low signal-to-noise ratio scenarios;

[0032] Figure 2 This is the result of uniformly moving 100 frames of original echo one-dimensional range images to frequency zero in step (2) of the specific implementation of the present invention;

[0033] Figure 3 is the high-precision amplitude distortion Ac obtained in step (7) of the specific embodiment of the present invention;

[0034] Figure 4 is the high-precision phase distortion φc obtained in step (7) of the specific embodiment of the present invention;

[0035] Figure 5 It is the original echo one-dimensional range image of a space target obtained in step (9) of the specific implementation method of the present invention and its one-dimensional range image after amplitude and phase compensation. DETAILED DESCRIPTION

[0036] Combine Figure 1-Figure 5 The implementation steps of the broadband amplitude-phase compensation method for low signal-to-noise ratio scenarios disclosed in the present invention are as follows:

[0037] Step 1: First, use the radar to transmit 100 frames of broadband pulses to the spherical satellite, and then receive 100 frames of broadband echo signals. After de-skewing, sampling, and velocity compensation, the de-skewing baseband original echo s is obtained. i (t), where i=1,2,…100.

[0038] Step 2: i (t) Perform Fourier transform to obtain 100 frames of original echo one-dimensional range image F i(f), where F i The center frequency of (f) is f 0i .

[0039] Step 3: In this embodiment, the sampling rate PF is 30MHz and the number of sampling points M is 1563 points. i (f) Make K i Circular left shift operation is performed to obtain G i (f), where K i For the closest An integer. Figure 2 As shown in FIG, through the cyclic left shift operation, the 100 frames of original echo one-dimensional range images have been uniformly moved to the vicinity of the frequency zero point.

[0040] Step 4: From Figure 2 It can be seen that G i The effective signal region of (f) is from -0.5MHz to 0.5MHz, so the frequency domain rectangular window function H(f) is constructed:

[0041] ,

[0042] Combine the rectangular window function with G i Multiply (f) and we get .

[0043] Step 5: J i (f) Perform inverse Fourier transform to obtain the windowed original echo j i (t).

[0044] Step 6: Get j i The normalized amplitude A of (t) i (t) and phase φ i (t).

[0045] Step 7: 100 groups of A i (t) with 100 sets of φ i (t) Perform averaging operations respectively to extract high-precision amplitude distortion A with low random error c and phase distortion φ c :

[0046] ,

[0047] ,

[0048] A c With φ c The specific results are as follows Figure 3 、 Figure 4 shown.

[0049] Step 8. The system's high-precision broadband amplitude and phase distortion compensation coefficient C(t) can be expressed as

[0050] .

[0051] Step 9: The broadband original echo of the radar detecting a space target is D(t). After Fourier transform, its broadband one-dimensional range image E(f) is obtained (e.g. Figure 5 Multiply C(t) and D(t) to obtain the space target echo I(t) after amplitude and phase distortion compensation. After further Fourier transformation, the wideband one-dimensional range image P(f) of the space target after amplitude and phase distortion compensation is obtained (as shown in the black solid line in the middle). Figure 5 (shown by the red dashed line in the middle). Figure 5 It can be seen that by adopting the broadband amplitude-phase compensation method described in the present invention, the HRRP main-to-sidelobe ratio of the space target can be improved from 0.2 dB (before compensation, black solid line) to 28 dB (after compensation, red dotted line), and the HRRP main-to-sidelobe ratio improvement effect is significant.

[0052] The present invention obtains high-quality broadband amplitude and phase distortion compensation coefficients based on the original broadband echo of a spherical satellite with a low signal-to-noise ratio, and extracts high-precision broadband amplitude and phase distortion parameters by utilizing multiple groups of broadband echo information of the spherical satellite. It does not require multi-pulse coherent accumulation, thus avoiding the problem of accurate calibration of multi-pulse phase deviations faced by traditional methods under low signal-to-noise ratio conditions. By performing frequency domain windowing processing on the original broadband echo of the spherical satellite, the signal-to-noise ratio is improved. By performing multi-pulse amplitude and phase separation and multi-pulse amplitude and phase averaging on the original broadband echo of the spherical satellite, the random errors of amplitude distortion and phase distortion are reduced, and then high-precision amplitude distortion and phase distortion parameters are extracted. The one-dimensional range image of the multi-pulse broadband echo is uniformly moved to near the frequency zero point through a cyclic shift operation.

[0053] In the above description, many specific details are set forth in order to fully understand the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios, characterized by: The steps include: Step 1: Get the baseband original echo s i (t); Step 2: i (t) Perform Fourier transform to obtain the original echo one-dimensional range image F i (f); Step 3: F i (f) Perform a circular left shift operation on point K to obtain G i (f), K is an integer; Step 4: Construct the frequency domain rectangular window function H i (f), the rectangular window function is combined with G i Multiply (f) and we get ; Step 5, J i (f) Perform inverse Fourier transform to obtain the windowed original echo j i (t); Step 6: Get j i The normalized amplitude A of (t) i (t) and phase ; Step 7: Normalize the amplitude A i (t) and phase Perform averaging operations respectively; Step 8, calculating the broadband amplitude and phase distortion compensation coefficient C(t); Step 9: directly multiply the broadband amplitude and phase distortion compensation coefficient C(t) by the broadband original echo D(t) detected by the radar from a target to obtain effective compensation for the amplitude and phase errors of the broadband original echo from the target; In step 1, N broadband pulses are transmitted to the spherical satellite, and N broadband echo signals are received. After de-skewing, frequency conversion, sampling, and velocity compensation, the de-skewing baseband original echo s is obtained. i (t), where i=1, 2,…, N.

2. The broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios according to claim 1, characterized in that: In step 3, F i The center frequency of (f) is f0; the system sampling rate is PF, the number of sampling points is M, and K is the closest An integer.

3. The broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios according to claim 2, characterized in that: In step 4, G i The spectrum of (f) shows that the effective signal area is f 1i to f 2i , then construct the frequency domain rectangular window function H i (f): 。 4. The broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios according to claim 3, characterized in that: In step six, j i The normalized amplitude A of (t) i (t) and phase The calculation method is: ， ， Among them, max[|j i (t)|] is|j i (t)|, Im[j i (t)] is j i The imaginary part of (t), Re[j i (t)] is j i The real part of (t).

5. The broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios according to claim 4, characterized in that: In step 7, the N normalized amplitudes A i (t) and phase Perform averaging operations respectively to obtain high-precision amplitude distortion A c and phase distortion : , 。 6. The broadband amplitude and phase distortion compensation method adapted to low signal-to-noise ratio scenarios according to claim 5, characterized in that: In step eight, C(t) is: 。

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