Indoor field radar pulse time-sharing slicing and echo synthesis method

Abstract

The invention provides an indoor field radar pulse time-sharing slicing and echo synthesis method. The method comprises the following steps: step 1, designing a radar pulse time-sharing slicing signal; setting the radar pulse signal as a linear frequency modulation signal, and performing time-sharing slicing: in order to ensure that the transmitted and received slice signals are not mutually coupled, enabling the pulse width to meet the condition that the back edge of the transmitted slice signal does not exceed the front edge of the received slice echo; step 2, echo synthesis design of slice signals; and carrying out time delay compensation on the mth section of slice echo, adding and synthesizing all the forward-moving slice echoes to obtain a complete target echo, and enabling the recovered target echo to pass through a linear frequency modulation signal matching filter to obtain a high-resolution one-dimensional range profile of the target. According to the method, time-sharing slicing processing is carried out on radar pulses, single-section slice signals are transmitted in a certain period, time delay compensation of slice echoes is carried out at a receiving end, then echo synthesis is carried out, and finally complete target echoes and a high-resolution one-dimensional range profile of a target are obtained.

Description

Technical field

[0001] The present invention relates to a method for time-sharing slicing and echo synthesis of indoor radar pulses, and belongs to the field of radar radiation simulation. In particular, it relates to a method for detecting and processing indoor radar pulse signals, and in particular to a method for acquiring high-resolution one-dimensional range profile features of a target by utilizing radar pulse slice echoes. [Background Technology]

[0002] Intermittent transmission and reception of radar signals involves splitting the pulse signal into multiple short pulses for transmission and reception, thereby resolving the mutual coupling problem between the transmit and receive signals in indoor environments. This provides an effective means for indoor pulse radar target detection and characteristic measurement. However, intermittent transmission and reception processing causes some information loss in the target echo. Typically, partial information of the target echo is used to reconstruct the complete target echo or to suppress false targets in high-resolution one-dimensional range images. Previous intermittent transmission and reception methods used windowing to suppress false targets in the range image or used sparse reconstruction methods to recover the true target echo, thereby obtaining the target's true range image as much as possible. However, these methods are constrained by target size and signal parameters, resulting in the loss of some detail in the target's high-resolution one-dimensional range image. The resulting range image differs from the true target range image, which is not conducive to extracting subtle target features from the range image.

[0003] By time-slicing the complete radar pulse, on the one hand, the short slice signal can solve the problem of mutual coupling between the transmitting and receiving signals in the indoor field. On the other hand, the echo of all the slice signals carries the complete information of the target. After all the slice signal echoes are time-delay compensated and then synthesized, the complete target echo can be obtained.

[0004] The present invention performs time-slicing design on indoor field radar pulses, performs time delay compensation and echo synthesis of slice echoes at the receiving end, obtains a complete target echo, and further obtains a high-resolution one-dimensional range image of the target. [Summary of the invention]

[0005] The problem addressed by the present invention is that existing range profile windowing and sparse reconstruction methods, which address the effects of intermittent transmission and reception on range profiles, are limited by target size and signal parameters. The resulting range profile differs from the true range profile, hindering the extraction of subtle target features. The present method uses time-slicing to process radar pulses, transmitting single-segment slice signals at a fixed period. Slice echoes are then time-delay compensated at the receiving end, followed by echo synthesis, ultimately yielding a complete target echo and a high-resolution one-dimensional range profile.

[0006] The present invention relates to an indoor radar pulse time-sharing slicing and echo synthesis method, and the technical solutions adopted are as follows:

[0007] The first step is the design of radar pulse time-slicing signal.

[0008] For a complete radar pulse signal s(t), taking a linear frequency modulation signal as an example, its pulse width is T. The linear frequency modulation signal s(t) is time-sliced: Assuming that there are M slices, the pulse width of a single slice signal is τ = T / M. To ensure that the transmitted and received slice signals are not coupled, the pulse width τ should satisfy the requirement that the trailing edge of the transmitted slice signal does not exceed the leading edge of the received slice echo; in addition, to ensure that the slice echo can be completely received, the repetition period of the transmitted slice signal is T s It should be satisfied that the leading edge of the next slice signal transmitted does not lag behind the trailing edge of the previous slice echo.

[0009] The second step is the echo synthesis design of the slice signal.

[0010] According to the first step, the echo of the mth slice is recorded as x m (t), where m = 1, 2, ..., M. The delay compensation is performed on the mth slice echo, that is, each slice echo is shifted forward by (m-1)(T s -τ), and then add all the slice echoes after the forward movement to get the complete target echo The recovered target echo y(t) is passed through the matched filter h(t) of the linear frequency modulation signal s(t) to obtain a high-resolution one-dimensional range image of the target.

[0011] The beneficial effects of the present invention mainly include:

[0012] First, a method for designing time-slicing signals for indoor field pulse radar signals is proposed. The designed pulse width of the slice signal prevents mutual coupling between the indoor field transmit and receive signals, and the designed transmit signal repetition period ensures that the slice echo is fully received without losing target information.

[0013] Second, a design method for synthesizing echoes from sliced ​​signals was proposed. Each slice echo contains a portion of target information. By aligning all the slice echoes with a certain time delay and then summing them together, a complete target echo is obtained. Compared to the target echo obtained by directly using the radar long pulse signal without the mutual coupling of the transmit and receive signals, the resulting target echo contains the same information.

Brief Description of the Drawings

[0014] Figure 1 It is the radar pulse time-sharing slicing and echo synthesis processing flow.

[0015] Figure 2(a) and Figure 2(b) are diagrams of indoor field slice signal transmission and slice echo reception scenes, respectively.

[0016] Figure 3(a), Figure 3(b), Figure 3(c) and Figure 3(d) are the target scattering center distribution diagram, linear frequency modulation signal waveform diagram, transmitted slice signal waveform diagram and received slice echo waveform diagram, respectively.

[0017] FIG4(a) and FIG4(b) are waveform diagrams of receiving a single-segment slice echo and performing delay compensation on the single-segment slice echo, respectively.

[0018] Figure 5(a) and Figure 5(b) are the target echo waveform synthesized from the slice echo and the high-resolution one-dimensional range image of the target, respectively.

Specific implementation method

[0019] The present invention is further described below with reference to the accompanying drawings. The present invention designs a method for time-sharing slicing and echo synthesis of indoor radar pulses, which comprises the following steps:

[0020] The first step is the design of radar pulse time-slicing signal.

[0021] For a complete pulse radar signal, taking a linear frequency modulation signal as an example, it can be expressed as:

[0022]

[0023] Where t is time, j is the imaginary unit, exp(·) is the exponential function with the natural constant as the base, T is the pulse width, μ = B / T is the frequency modulation slope, B is the signal bandwidth, f c is the carrier frequency, rect(·) is the rectangular pulse, recorded as:

[0024]

[0025] The complete linear frequency modulation signal s(t) is time-sliced. Assuming there are M slice signals, the mth slice signal is:

[0026]

[0027] Where τ = T / M is the slice signal pulse width. Usually the target can be decomposed into several scattering centers. Assuming there are N scattering centers, the scattering coefficient of the nth scattering center is α n , the distance of the signal from the radar antenna to the nth scattering center is R n . Record the shortest distance R min and the longest distance R max They are:

[0028] R min =min{R1,R2,...,R N} (4)

[0029] R max=max{R1,R2,...,R N} (5)

[0030] Among them, min{·} and max{·} represent the minimum and maximum values ​​of the sequence respectively, L=R max -R min Usually the size of the target. To avoid mutual coupling between the transmitting and receiving signals, the slice signal pulse width τ must ensure that the mth slice signal has been transmitted when the mth slice echo arrives, and must meet the following requirements:

[0031]

[0032] Where C is the electromagnetic wave velocity. In addition, to ensure that the slice echo can be received completely, the repetition period of the slice signal T s It is necessary to ensure that when the m+1th slice signal is transmitted, the mth slice echo has been completely received, which must meet the following requirements:

[0033]

[0034] The total transmitted signal s T (t) is expressed as:

[0035]

[0036] The second step is the echo synthesis design of the slice signal.

[0037] For the mth slice echo, it is composed of N scattering centers reflecting the mth slice signal, which can be expressed as:

[0038]

[0039] Total received echo x R (t) is expressed as:

[0040]

[0041] Shift the mth slice echo forward by (m-1)(T s -τ), and then the echoes are added together to obtain the synthesized target echo y(t):

[0042]

[0043] It can be seen that the synthesized target echo is the same as the target echo of the linear frequency modulation signal s(t) under the premise of no mutual coupling between the transmitting and receiving signals. This shows that the pulse time slicing and echo synthesis method of the present invention can not only avoid the mutual coupling between the transmitting and receiving signals in the indoor field, but also ensure that the synthesized target echo does not lose the target information. The synthesized target echo y(t) is sent to the matched filter h(t) = s *(-t), where * represents the complex conjugate, and the output |s D (R)| is the high-resolution one-dimensional range image of the target, which is recorded as:

[0044]

[0045] Where R represents the distance relative to the radar, Denotes convolution, sinc(x) = sin(πx) / (πx). Each scattering center of the target will appear as a peak in the range image.

[0046] Assume that the linear frequency modulation signal bandwidth is B = 500MHz, the pulse width is T = 20μs, the number of slices is M = 100 segments, the signal width of a single segment is τ = T / M = 0.2μs, and the repetition period is T s = 2μs, the number of scattering centers of the target is N = 5, the coordinates of each scattering center are R = 45 + [-4.5, -2.7, 0, 3.3, 5.4] meters, and the scattering coefficients of each scattering center are α = [0.5, 0.31, 1, 0.42, 0.76]. Without loss of generality, for simplicity, take the demodulated baseband signal as an example, and assume that the carrier frequency f c =0.

[0047] according to Figure 1 The simulation is performed according to the flowchart shown. To avoid mutual coupling between transmit and receive signals in the indoor field, the transmit and receive antennas operate alternately. When transmitting a slice signal, the transmit and receive antennas operate as shown in Figure 2(a), with the transmit antenna on and the receive antenna off. When receiving a slice signal, the transmit and receive antennas operate as shown in Figure 2(b), with the receive antenna on and the transmit antenna off. Assume that the target's scattering centers are arranged as shown in Figure 3(a), located at 40.5 meters, 42.3 meters, 45.0 meters, 48.3 meters, and 50.4 meters, respectively. The waveform of a complete linear frequency modulation signal is shown in Figure 3(b), which becomes increasingly dense over time. This linear frequency modulation signal is time-sliced ​​with a pulse width of 0.2 μs, resulting in 100 slice signals. Figure 3(c) shows the time domain process of the three slice signals before transmission, with each slice signal separated by 2 μs. After being scattered by the target, the waveform of the total received slice echo is shown in Figure 3(d). Each slice echo is synthesized by the echoes of 5 scattering points, and the echoes of two adjacent slices do not overlap. The slice echoes of the first three segments are shown in Figure 4(a). Each slice echo has no time intersection. Delay compensation is performed on each slice echo, and the slice echo of the kth segment is shifted forward by (k-1) (T s-τ). After delay compensation, the first three slice echoes are shown in Figure 4(b). At this point, each slice echo has temporal intersection. All delay-compensated slice echoes are summed to produce the synthesized target echo shown in Figure 5(a). The synthesized target echo has an envelope fluctuation characteristic, implicitly indicating the relative positions of multiple scattering centers. Using the synthesized target echo, a high-resolution one-dimensional range image of the target is obtained by applying a matched filter to the linear frequency modulation signal, as shown in Figure 5(b). The image shows five target peaks located at 40.5 m, 42.3 m, 45.0 m, 48.3 m, and 50.4 m, respectively. The obtained positions are consistent with the preset scattering center positions, and the high-resolution one-dimensional range image is consistent with that of the original echo in the absence of coupling.

Claims

1. A method for time-sharing slicing and echo synthesis of indoor radar pulses, characterized in that: The steps are as follows: Step 1: radar pulse time-slicing signal design; For a complete radar pulse signal s(t), the pulse width is T. Assume that the radar pulse signal is a linear frequency modulation signal and perform time slicing: Assume that there are M slices in total, then the pulse width of a single slice signal is τ = T / M; to ensure that the transmitting and receiving slice signals are not mutually coupled, the pulse width τ should satisfy that the trailing edge of the transmitted slice signal does not exceed the leading edge of the received slice echo; in addition, to ensure that the slice echo can be completely received, the repetition period of the transmitted slice signal is T s It should be satisfied that the leading edge of the next slice signal transmitted does not lag behind the trailing edge of the previous slice echo; Step 2: echo synthesis design of slice signal; Let the mth slice echo be x m (t), where m = 1, 2, ..., M; delay compensation is performed on the mth slice echo, that is, each slice echo is shifted forward by (m-1)(T s -τ), and then add all the slice echoes after the forward movement to get the complete target echo The recovered target echo y(t) is passed through the matched filter h(t) of the linear frequency modulation signal s(t) to obtain a high-resolution one-dimensional range image of the target.

2. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1, wherein: In step 1, a complete pulse radar signal, i.e., a linear frequency modulation signal, is expressed as: Where t is time, j is the imaginary unit, exp(·) is the exponential function with the natural constant as the base, T is the pulse width, μ = B / T is the frequency modulation slope, B is the signal bandwidth, f c is the carrier frequency, rect(·) is the rectangular pulse, recorded as:

3. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1 or 2, characterized in that: The complete linear frequency modulation signal s(t) is time-sliced. Assuming there are M slice signals, the mth slice signal is: Wherein, τ=T / M is the slice signal pulse width.

4. The method for indoor radar pulse time-sharing slicing and echo synthesis according to claim 1, characterized in that: There are N scattering centers in total, and the scattering coefficient of the nth scattering center is α n , the distance of the signal from the radar antenna to the nth scattering center is R n ;Remember the shortest distance R min and the longest distance R max They are: R min =min{R1,R2,...,R N } (4) R max =max{R1,R2,...,R N } (5) Among them, min{·} and max{·} represent the minimum and maximum values ​​of the sequence respectively, L=R max -R min is the size of the target.

5. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1, characterized in that: To avoid mutual coupling between the transmitting and receiving signals, the slice signal pulse width τ must ensure that the mth slice signal has been transmitted when the mth slice echo arrives, and must satisfy the following conditions: Where C is the electromagnetic wave velocity; in addition, to ensure that the slice echo can be completely received, the repetition period of the slice signal T s It is necessary to ensure that when the m+1th slice signal is transmitted, the mth slice echo has been completely received, which must meet the following requirements:

6. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1, characterized in that: The total transmitted signal s T (t) is expressed as:

7. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1 or 5, characterized in that: In step 2, the mth slice echo is composed of N scattering centers reflecting the mth slice signal, which can be expressed as:

8. The method for indoor radar pulse time-slicing and echo synthesis according to claim 1, characterized in that: Total received echo x R (t) is expressed as:

9. The method for indoor radar pulse time-slicing and echo synthesis according to claim 7, characterized in that: Shift the mth slice echo forward by (m-1)(T s -τ), and then the echoes are added together to obtain the synthesized target echo y(t): The synthesized target echo is the same as the target echo of the linear frequency modulation signal s(t) without the mutual coupling of the transmitting and receiving signals; It can avoid the mutual coupling phenomenon of indoor field transmitting and receiving signals, and ensure that the synthesized target echo will not lose the target information.

10. The method for indoor radar pulse time-slicing and echo synthesis according to claim 9, characterized in that: The synthesized target echo y(t) is sent to the matched filter h(t) = s * (-t), where * represents the complex conjugate, and the output |s D (R)| is the high-resolution one-dimensional range image of the target, which is recorded as: Where R represents the distance relative to the radar, Represents convolution, sinc(x) = sin(πx) / (πx); each scattering center of the target will appear as a peak in the range image.

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