阅读说明：本技术 一种动目标检测滤波器组的优化设计方法 (Optimization design method of moving target detection filter bank ) 是由 陈希信 王洋 李坡 弓盼 张庆海 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种动目标检测滤波器组的优化设计方法,包括以下步骤：1)建立零频率动目标检测滤波器的优化设计准则,并求解此滤波器的单位脉冲响应；2)将所求解的单位脉冲响应分别搬移到一组预先设定的非零频点上,利用所有的单位脉冲响应构造动目标检测滤波器组；3)利用动目标检测滤波器组处理雷达接收信号,实现地物杂波抑制和目标信号增强。在保持设计滤波器与参考滤波器的多普勒频率分辨率相同、信噪比增益相同的情况下,通过使各动目标检测滤波器在设定频率处的响应为零,能显著地提高雷达系统的改善因子,并且可以通过快速傅里叶变换实现,因此具有较高的计算效率。(The invention discloses an optimal design method of a moving target detection filter bank, which comprises the following steps: 1) establishing an optimal design rule of a zero-frequency moving target detection filter, and solving a unit impulse response of the filter; 2) moving the solved unit impulse responses to a group of preset non-zero frequency points respectively, and constructing a moving target detection filter bank by using all the unit impulse responses; 3) and processing a radar receiving signal by using a moving target detection filter bank to realize clutter suppression of ground objects and target signal enhancement. Under the condition that the Doppler frequency resolution and the signal-to-noise ratio gain of the designed filter and the reference filter are kept the same, the response of each moving target detection filter at the set frequency is zero, the improvement factor of the radar system can be remarkably improved, and the radar system can be realized through fast Fourier transform, so that the radar system has higher calculation efficiency.)

1. An optimal design method for a moving target detection filter bank is characterized by comprising the following steps:

1) establishing an optimal design rule of a zero-frequency moving target detection filter, and solving a unit impulse response of the filter;

2) moving the solved unit impulse responses to a group of preset non-zero frequency points respectively, and constructing a moving target detection filter bank by using all the unit impulse responses;

3) and processing a radar receiving signal by using a moving target detection filter bank to realize clutter suppression of ground objects and target signal enhancement.

2. The method according to claim 1, wherein the moving object detection filter bank comprises: the step 1) establishes an optimal design rule of a zero-frequency moving target detection filter, and solves the unit impulse response of the filter, specifically,

1-1) zero frequency moving target detection filter, namely the optimization design rule of a zero frequency MTD filter is as follows,

in the formula: g₀For a known reference moving object detection filter, i.e. the unit impulse response of the reference MTD filter, h₀For the unit impulse response of the zero frequency MTD filter to be designed, superscript H denotes taking the conjugate transpose, superscript T denotes taking the transpose, s.t. denotes being limited, matrix R is defined as,

in the formula:time domain steering vector as target, f frequency, K number of coherent pulses received by radar, and T_rIs the pulse repetition period of the radar, j is an imaginary unit, j²-1, Δ f is the frequency range around the zero frequency point;

1-2) solving the formula (1) by Lagrange multiplier method to obtain unit impulse response h of zero frequency MTD filter to be designed₀，

h₀＝μR^-1g₀+g₀ (3)

In the formula:is Lagrange multiplier.

3. The method according to claim 2, wherein the moving object detection filter bank comprises: the step 2) respectively moves the solved unit impulse responses to a group of preset non-zero frequency points, and constructs a moving target detection filter bank by using all the unit impulse responses, specifically,

2-1) presetting a group of non-zero frequency points, i.e. f_k＝k/(KT_r) K-1, the unit impulse response h of the zero-frequency MTD filter to be designed to be solved₀Respectively moving to the group of non-zero frequency points to obtain the unit impulse response h of the non-zero frequency MTD filter to be designed_k，

h_k＝h₀⊙a_k，k＝1,2,...,K-1 (4)

In the formula:as an Hadamard product,

will reference the unit impulse response g of the MTD filter₀Respectively moving to the group of non-zero frequency points to obtain unit impulse response g of the non-zero frequency reference MTD filter_k，

g_k＝g₀⊙a_k，k＝1,2,...,K-1 (5)

2-2) using all unit impulse responses h of the designed MTD filter_kA filter bank H is constructed and designed,

H＝[h₀,h₁,…,h_K-1] (6)

unit impulse response g using all reference MTD filters_kA reference filter bank G is constructed which,

G＝[g₀,g₁,…,g_K-1] (7)。

4. the method according to claim 3, wherein the moving object detection filter bank comprises: the step 3) utilizes the moving target detection filter bank to process the radar receiving signal to realize the clutter suppression of the ground object and the target signal enhancement, in particular,

3-1) setting the radar reception signal as z, which contains ground clutter c with a Doppler frequency near zero, a target echo signal s with a Doppler frequency far from zero, and white Gaussian noise n, i.e. the radar reception signal z,

z＝c+s+n (8)

3-2) processing the radar receiving signal z by using the designed filter bank H to obtain a designed filter bank output signal x, and processing the radar receiving signal z by using the reference filter bank G to obtain a reference filter bank output signal y, namely

x＝H^Hz，y＝G^Hz (9)

After the processing of the formula (9), the ground clutter c in the output signal x of the designed filter bank is suppressed, the target signal s is enhanced, and the ground clutter c in the output signal y of the reference filter bank is larger than the ground clutter c in the output signal x of the designed filter bank.

Technical Field

The invention relates to optimization of a moving target detection filter bank, in particular to an optimization design method of the moving target detection filter bank.

Background

The Doppler frequency of ground clutter and the Doppler frequency of moving target echoes in radar receiving signals are usually different, so that the ground clutter can be suppressed by using a moving target detection filter bank, the signal-to-noise ratio of target echo signals is improved, and the moving target detection filter bank is usually designed and realized by using fast Fourier transform.

When radar received signals are processed through fast Fourier transform, the response of a moving target detection filter bank at a zero frequency is zero, so that ground clutter is suppressed, but as the side lobe of the filter is higher, when a clutter spectrum is widened to a certain extent, the performance of moving target detection is obviously reduced, and small target signals are easily covered by large target signals. Therefore, the side lobe level of the filter is usually reduced by using a tapering window function, but the signal-to-noise ratio of the target echo signal is lost, and the zero response position of the filter after windowing is shifted, so that the residual of the clutter of the ground objects is increased, and the system improvement factor is reduced.

Disclosure of Invention

The invention aims to provide an optimal design method of a moving target detection filter bank, which can remarkably improve the improvement factor of a radar system by enabling the response of each moving target detection filter at a set frequency to be zero under the condition of keeping the same Doppler frequency resolution and the same signal-to-noise ratio gain of a designed filter and a reference filter, and can be realized by fast Fourier transform, thereby having higher calculation efficiency.

In order to achieve the above object, according to one aspect of the present invention, the present invention provides the following technical solutions:

an optimal design method for a moving target detection filter bank comprises the following steps:

1) establishing an optimal design rule of a zero-frequency moving target detection filter, and solving a unit impulse response of the filter;

2) moving the solved unit impulse responses to a group of preset non-zero frequency points respectively, and constructing a moving target detection filter bank by using all the unit impulse responses;

3) and processing a radar receiving signal by using a moving target detection filter bank to realize clutter suppression of ground objects and target signal enhancement.

The invention is further configured to: the step 1) establishes an optimal design rule of a zero-frequency moving target detection filter, and solves the unit impulse response of the filter, specifically,

1-1) zero frequency moving target detection filter, namely the optimization design rule of a zero frequency MTD filter is as follows,

in the formula: g₀For a known reference moving object detection filter, i.e. the unit impulse response of the reference MTD filter, h₀For the unit impulse response of the zero frequency MTD filter to be designed, superscript H denotes taking the conjugate transpose, superscript T denotes taking the transpose, s.t. denotes being limited, matrix R is defined as,

in the formula:time domain steering vector as target, f frequency, K number of coherent pulses received by radar, and T_rIs the pulse repetition period of the radar, j is an imaginary unit, j²-1, Δ f is the frequency range around the zero frequency point;

1-2) solving the formula (1) by Lagrange multiplier method to obtain unit impulse response h of zero frequency MTD filter to be designed₀，

h₀＝μR^-1g₀+g₀ (3)

In the formula:is Lagrange multiplier.

The invention is further configured to: the step 2) respectively moves the solved unit impulse responses to a group of preset non-zero frequency points, and constructs a moving target detection filter bank by using all the unit impulse responses, specifically,

2-1) presetting a group of non-zero frequency points, i.e. f_k＝k/(KT_r) K-1, the unit impulse response h of the zero-frequency MTD filter to be designed to be solved₀Respectively moving to the group of non-zero frequency points to obtain the unit impulse response h of the non-zero frequency MTD filter to be designed_k，

h_k＝h₀⊙a_k，k＝1,2,...,K-1 (4)

In the formula:as an Hadamard product,

will reference the unit impulse response g of the MTD filter₀Respectively moving to the group of non-zero frequency points to obtain unit impulse response g of the non-zero frequency reference MTD filter_k，

g_k＝g₀⊙a_k，k＝1,2,...,K-1 (5)

2-2) using all unit impulse responses h of the designed MTD filter_kA filter bank H is constructed and designed,

H＝[h₀,h₁,...,h_K-1] (6)

unit impulse response g using all reference MTD filters_kA reference filter bank G is constructed which,

G＝[g₀,g₁,...,g_K-1] (7)。

the invention is further configured to: the step 3) utilizes the moving target detection filter bank to process the radar receiving signal to realize the clutter suppression of the ground object and the target signal enhancement, in particular,

3-1) setting the radar reception signal as z, which contains ground clutter c with a Doppler frequency near zero, a target echo signal s with a Doppler frequency far from zero, and white Gaussian noise n, i.e. the radar reception signal z,

z＝c+s+n (8)

3-2) processing the radar receiving signal z by using the designed filter bank H to obtain a designed filter bank output signal x, and processing the radar receiving signal z by using the reference filter bank G to obtain a reference filter bank output signal y, namely

x＝H^Hz，y＝G^Hz (9)

After the processing of the formula (9), the ground clutter c in the output signal x of the designed filter bank is suppressed, the target signal s is enhanced, and the ground clutter c in the output signal y of the reference filter bank is larger than the ground clutter c in the output signal x of the designed filter bank.

Compared with the prior art, the invention has the advantages that: under the condition that the Doppler frequency resolution and the signal-to-noise ratio gain of the designed filter and the reference filter are kept the same, the response of each moving target detection filter at the set frequency is zero, the improvement factor of the radar system can be remarkably improved, and the radar system can be realized through fast Fourier transform, so that the radar system has higher calculation efficiency.

Drawings

FIG. 1 is a flow chart of an optimized design method for a moving target detection filter bank according to the present invention;

FIG. 2 is a comparison of the amplitude-frequency response of a designed filter and a reference filter in an optimized design method of a moving target detection filter bank according to the present invention;

FIG. 3 is a comparison of the outputs of the simulation signal through the two filter banks for the method of the present invention for optimizing the design of the moving target detection filter bank;

FIG. 4 is an autoregressive model cepstra of an optimized design method of a moving target detection filter bank according to the present invention;

FIG. 5 is a main lobe of a clutter spectrum of an optimized design method of a moving target detection filter bank according to the present invention;

FIG. 6 is a table comparing the improvement factors of the optimal design method for the moving target detection filter bank according to the present invention;

fig. 7 is a comparison of outputs of two filter banks of actually measured radar data according to the optimal design method for a moving target detection filter bank of the present invention.

Detailed Description

The invention is further described with reference to the accompanying drawings.

The invention provides an optimal design method of a moving target detection filter bank, which can remarkably improve the improvement factor of a radar system by enabling the response of each moving target detection filter at a set frequency to be zero under the condition of keeping the same Doppler frequency resolution and the same signal-to-noise ratio gain of a designed filter and a reference filter, and can be realized by fast Fourier transform, thereby having higher calculation efficiency.

An optimal design method for a moving target detection filter bank comprises the following steps:

1) establishing an optimal design rule of a zero-frequency moving target detection filter, and solving a unit impulse response of the filter;

in particular to a method for preparing a high-performance nano-silver alloy,

the step 1) establishes an optimal design rule of a zero-frequency moving target detection filter, and solves the unit impulse response of the filter, specifically,

1-1) zero frequency moving target detection filter, namely the optimization design rule of a zero frequency MTD filter is as follows,

in the formula: g₀For a known reference moving object detection filter, i.e. the unit impulse response of the reference MTD filter, h₀For the unit impulse response of the zero frequency MTD filter to be designed, superscript H denotes taking the conjugate transpose, superscript T denotes taking the transpose, s.t. denotes being limited, matrix R is defined as,

in the formula:time domain steering vector as target, f frequency, K number of coherent pulses received by radar, and T_rIs the pulse repetition period of the radar, j is an imaginary unit, j²-1, Δ f is the frequency range around the zero frequency point;

1-2) solving the formula (1) by Lagrange multiplier method to obtain unit impulse response h of zero frequency MTD filter to be designed₀，

h₀＝μR^-1g₀+g₀ (3)

In the formula:is Lagrange multiplier.

2) Moving the solved unit impulse responses to a group of preset non-zero frequency points respectively, and constructing a moving target detection filter bank by using all the unit impulse responses;

in particular to a method for preparing a high-performance nano-silver alloy,

2-1) presetting a group of non-zero frequency points, i.e. f_k＝k/(KT_r) K-1, the unit impulse response h of the zero-frequency MTD filter to be designed to be solved₀Respectively moving to the group of non-zero frequency points to obtain the unit impulse response h of the non-zero frequency MTD filter to be designed_k，

h_k＝h₀⊙a_k，k＝1,2,...,K-1 (4)

In the formula:as an Hadamard product,

will reference the unit impulse response g of the MTD filter₀And also shifted to the set of non-zero frequency points respectively to obtain a non-zero frequency reference MTD filterUnit impulse response g_k，

g_k＝g₀⊙a_k，k＝1,2,...,K-1 (5)

2-2) using all unit impulse responses h of the designed MTD filter_kA filter bank H is constructed and designed,

H＝[h₀,h₁,...,h_K-1] (6)

unit impulse response g using all reference MTD filters_kA reference filter bank G is constructed which,

G＝[g₀,g₁,...,g_K-1] (7)。

3) processing radar receiving signals by using a moving target detection filter bank to realize clutter suppression of ground objects and target signal enhancement;

in particular to a method for preparing a high-performance nano-silver alloy,

3-1) setting the radar reception signal as z, which contains ground clutter c with a Doppler frequency near zero, a target echo signal s with a Doppler frequency far from zero, and white Gaussian noise n, i.e. the radar reception signal z,

z＝c+s+n (8)

3-2) processing the radar receiving signal z by using the designed filter bank H to obtain a designed filter bank output signal x, and processing the radar receiving signal z by using the reference filter bank G to obtain a reference filter bank output signal y, namely

x＝H^Hz，y＝G^Hz (9)

After the processing of the formula (9), the ground clutter c in the output signal x of the designed filter bank is suppressed, the target signal s is enhanced, and the ground clutter c in the output signal y of the reference filter bank is larger than the ground clutter c in the output signal x of the designed filter bank.

The optimization design method of the moving target detection filter bank is adopted for simulation, and the optimization design method is verified through simulation examples and actual measurement radar data.

Let reference filter g₀For a 16-order 45dB Chebyshev filter, the frequency range delta f around the zero frequency point is pi/20, and the zero frequency MTD filter h is designed according to the method₀. The amplitude-frequency response of the designed zero-frequency MTD filter and the amplitude-frequency response of the reference filter are shown in fig. 2. As can be seen from fig. 2: designing a filter to have the same main lobe of amplitude-frequency response as a reference filter, and indicating that the two filters have the same Doppler frequency resolution; and the amplitude-frequency response of the designed filter is zero at 12 frequency points with relative frequency k' of +/-2, +/-3, +/-4, +/-5, +/-6 and +/-7, so that the design aim is achieved, and the amplitude-frequency response of the reference filter at the above 12 frequency points is not necessarily zero.

Since the SNR gain of the designed filter bank H, i.e. the SNR gain, cannot be calculated by a formula, but the SNR gain of the reference filter bank G can be calculated, the SNR gain of the designed filter bank needs to be examined by monte-carlo simulation. The simulation signal is composed of a sine signal and a white gaussian noise, and is input into the design filter bank and the reference filter bank respectively, and the output is shown in fig. 3. As can be seen from fig. 3, the outputs of the design filter bank and the reference filter bank are the same, and therefore the signal-to-noise ratio of the outputs is also the same, and thus the SNR gains of both are also the same.

The simulated clutter spectrum model adopts an autoregressive model C (f)_d)，

C(f_d)＝[1-0.98exp(-j2πf_dT_r)]^-2 (10)

The clutter spectrum is shown in FIG. 4 for a pulse repetition frequency f_r＝1/T_rThe frequency at which the clutter spectrum mainlobe drops by 3dB is ± 6Hz, as shown in fig. 5. The spur is used as an input to the MTD filter bank, and the improvement factors for the design filter bank H and the reference filter bank G are calculated, as shown in fig. 6. As can be seen from the table in fig. 6, the improvement factor of the design filter bank is improved by about 41dB on average over the reference filter bank for a given ground clutter model.

In the experiment, a radar transmits 16 coherent pulses, a radar receiving signal comprises ground clutter, a target echo and receiver noise, the radar receiving signal is respectively input into a design filter bank H and a reference filter bank G for processing, the result is shown in figure 7, it can be seen that the main lobe clutter of the radar receiving signal and the main lobe clutter of the reference filter bank are the same, but the minor lobe clutter leakage of the reference filter bank covers weak target signals, so that the target signals cannot be detected, the design filter bank effectively inhibits the ground clutter, namely the improvement factor of the design filter bank is obviously improved, the target signals are highlighted, and therefore the detection is easy.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.