阅读说明：本技术 一种间歇采样转发干扰的参数辨识方法 (Parameter identification method for intermittent sampling forwarding interference ) 是由 于雷 位寅生 孟芸芸 陈雨时 沙明辉 李迎春 于 2019-11-08 设计创作，主要内容包括：一种间歇采样转发干扰的参数辨识方法,解决了现有间歇采样转发干扰的参数辨识方法复杂的问题,属于雷达有源干扰对抗技术领域。所述方法包括：S1、利用截断矩形窗对雷达回波进行分段,对每段信号进行最优阶次分数阶傅里叶变换,再进行拼接；S2、改变截断矩形窗的长度,利用S1获得多个拼接的信号,搜索出所述多个拼接信号中复杂度最低的信号x<Sub>opt</Sub>(u),并根据信号x<Sub>opt</Sub>(u)的分布特性,辨识出干扰参数的估计结果。根据处理结果峰值脉冲的分布特性及辨识出的参数,可以实现干扰的具体转发策略的精细化辨识；采用线性调频信号的分数阶傅里叶变换滤波技术,可以滤除干扰信号保留目标信号,同时去除噪声,从而实现间歇采样转发干扰的对抗。(A parameter identification method for intermittent sampling forwarding interference solves the problem that the existing parameter identification method for intermittent sampling forwarding interference is complex, and belongs to the technical field of radar active interference countermeasure. The method comprises the following steps: s1, segmenting radar echoes by using a truncated rectangular window, performing optimal order fractional Fourier transform on each segment of signals, and splicing; s2, changing the length of the truncated rectangular window, obtaining a plurality of spliced signals by utilizing S1, and searching out the signal x with the lowest complexity in the spliced signals opt (u) and according to the signal x opt (u) identifying the estimation result of the interference parameter. According to the distribution characteristics of the processing result peak value pulse and the identified parameters, the detailed identification of the interference specific forwarding strategy can be realized; by adopting the fractional Fourier transform filtering technology of the linear frequency modulation signals, the interference signals can be filtered, the target signals are reserved, and simultaneously, the noise is removed, so that the countermeasure of the intermittent sampling forwarding interference is realized.)

1. A method for identifying parameters of intermittent sampling forwarding interference (SRI), the method comprising:

s1, segmenting radar echoes by using a truncated rectangular window, performing optimal order fractional Fourier transform on each segment of signals, and splicing;

s2, changing the length of the truncated rectangular window, obtaining a plurality of spliced signals by utilizing S1, and searching out the signal x with the lowest complexity in the spliced signals_opt(u) and according to the signal x_opt(u) identifying the estimation result of the interference parameter.

2. The method of claim 1, wherein the estimation result of the interference parameter comprises a slice width T_ISampling times N and forwarding times M;

when x is_opt(u) the peaks are uniformly distributed, the distance between each two adjacent peaks is equal, and the distance between adjacent peaks is equalFor a sampling period T_uWidth of slice T_IFor a sampling period T_uHalf of (1), the number of forwarding times M ═ T_u/T_I-1, number of slice samples within a single pulse

when x is_opt(u) the distance between each adjacent peak is unequal, the peaks exhibit periodic distribution, and the minimum repetition period is the sampling period T_uWidth of slice T_IEqual to the length of the rectangular window, and the forwarding times M equal to T_u/T_I-1, number of slice samples within a single pulse

when xo_pt(u) the distance between each adjacent peak is unequal, the distribution of the peaks has no periodic characteristics, and the maximum value of the distance between adjacent peaks is the sampling period T_uNumber of slice samples within a single pulse

3. The method of claim 2, wherein the method further comprises:

according to the signal x_opt(u) determining a strategy of forwarding interference by intermittent sampling according to the distribution characteristics and the estimation result of the interference parameters, specifically:

when x is_opt(u) the peaks are uniformly distributed, the distance between every two adjacent peaks is equal, and an intermittent sampling direct forwarding interference strategy is adopted;

when x is_opt(u) the distance between each adjacent peak is unequal, the peaks are in periodic distribution, the maximum adjacent peak distance is twice of the minimum adjacent peak distance, and an intermittent sampling repeated forwarding interference strategy is adopted;

when x is_opt(u) of each adjacent peakThe distance between the two adjacent wave peaks is unequal, the wave crest distribution has no periodic characteristic, and intermittent sampling circulation forwarding interference is adopted.

4. The method of claim 2, wherein the method further comprises:

determining the position of interference according to the interference parameter estimation result, constructing a narrow-band filter for interference filtering, and realizing interference suppression, specifically comprising the following steps:

s31, calculating the optimal order a of the fractional Fourier transform of the transmitting linear frequency modulation signal:

s32, performing fractional Fourier transform on the radar echo by using the calculated optimal order a:

wherein, K_α(t, u) is the kernel function, α ═ a π/2, S_r(t) represents a radar echo signal;

s33, and for the obtained S_α(u) performing a maximum search to determine the position of the maximum, which is the position of the interference signal in the fractional domain, with a lag (K) relative to the position of the target signal_rT_wN_s/2f_s)sin(2π-α)-cos(2π-α)T_IFurther determining the position of the target signal in the fractional domain;

s34, constructing a narrow-band filter for the position of the target signal in the fractional domain, and dividing S_α(u) inputting the signal into the narrow-band filter for filtering, and realizing the filtering of interference and the reservation of the position of a target signal;

and S35, performing fractional Fourier inverse transformation on the filtered signal to obtain a time domain signal after interference suppression.

Technical Field

The invention relates to an identification method and a countermeasure method of intermittent sampling forwarding interference, and belongs to the technical field of radar active interference countermeasure.

Background

With the large-scale application of jammers based on the digital radio frequency storage technology in actual combat, the complexity of interference signals is further improved. Intermittent sampling and forwarding interference is rapidly developed based on the capability of a digital radio frequency memory to intercept and store radar transmission signals, and the interference to radar is mainly realized by intermittently sampling and forwarding a single radar pulse signal. The jammer intercepts the large-time-width radar signal, processes and forwards a small segment of signal immediately after high-fidelity sampling, then samples, processes and forwards the next segment, and the sampling and forwarding alternately work in time-sharing mode until the large-time-width signal is finished, so that intermittent sampling and forwarding interference is formed.

Intermittent sample forward interference is highly correlated with radar signals, can generate processing gain and form a plurality of false target groups in distance, and the false targets are distributed in front of real targets (the false targets are closer to the radar than the real targets), and can form multi-false target suppression interference on the radar. In addition, the receiving and sending strategies of the interference are flexible and changeable, different interference modes can be corresponded by changing related parameter settings, interference signals which are highly vivid with radar echo signals in a plurality of parameter domains are generated, and the difficulty of interference identification and countermeasures is increased. The parameters of different interference signals correspond to different interference strategies, typical interference modes are intermittent sampling direct forwarding interference, intermittent sampling repeated forwarding interference and intermittent sampling circulating forwarding interference, the parameter estimation of an interference pattern can realize the refined identification of an interference type and a strategy, and can also be used for subsequent interference suppression, wherein the key is the estimation of three parameters, including the number of slices, the forwarding times and the width of the slices. The existing interference suppression adopts a reconstruction cancellation method to suppress interference, but the method has higher requirements on the estimation accuracy and the dry-to-noise ratio of the identified parameters, and the existing methods for identifying the three parameters are complex and have difficulty in meeting the requirements on accuracy.

Disclosure of Invention

Aiming at the problem that the existing parameter identification method for intermittent sampling forwarding interference is complex, the invention provides a simple and high-precision parameter identification method for intermittent sampling forwarding interference.

The invention discloses a parameter identification method for intermittent sampling forwarding interference, which comprises the following steps:

s1, segmenting radar echoes by using a truncated rectangular window, performing optimal order fractional Fourier transform on each segment of signals, and splicing;

s2, changing the length of the truncated rectangular window, obtaining a plurality of spliced signals by utilizing S1, and searching out the signal x with the lowest complexity in the spliced signals_opt(u) and according to the signal x_opt(u) identifying the estimation result of the interference parameter.

Preferably, the estimation result of the interference parameter includes a slice width T_ISampling times N and forwarding times M;

when x is_optThe wave crests of (u) are uniformly distributed, the distance between every two adjacent peaks is equal, and the distance between every two adjacent peaks is a sampling period T_uWidth of slice T_IIs T_uHalf of (1), the number of forwarding times M ═ T_u/T_I-1, number of slice samples within a single pulse

T_wRepresents the pulse width;

when x is_opt(u) the distance between each adjacent peak is unequal, the peaks exhibit periodic distribution, and the minimum repetition period is the sampling period T_uWidth of slice T_IEqual to the length of the rectangular window, and the forwarding times M equal to T_u/T_I-1, number of slice samples within a single pulseT_wRepresents the pulse width;

when x is_opt(u) the distance between each adjacent peak is unequal, the distribution of the peaks has no periodic characteristics, and the maximum value of the distance between adjacent peaks is the sampling period T_uNumber of slice samples within a single pulse

Preferably, the method further comprises:

according to the signal x_opt(u) determining a strategy of forwarding interference by intermittent sampling according to the distribution characteristics and the estimation result of the interference parameters, specifically:

when x is_opt(u) the peaks are uniformly distributed, the distance between every two adjacent peaks is equal, and an intermittent sampling direct forwarding interference strategy is adopted;

when x is_opt(u) the distance between each adjacent peak is unequal, the peaks are in periodic distribution, the maximum adjacent peak distance is twice of the minimum adjacent peak distance, and an intermittent sampling repeated forwarding interference strategy is adopted;

when x is_opt(u) the distance between every two adjacent peaks is unequal, the distribution of the peaks has no periodic characteristic, and intermittent sampling circulation is adopted to forward interference.

Preferably, the method further comprises:

determining the position of interference according to the interference parameter estimation result, constructing a narrow-band filter for interference filtering, and realizing interference suppression, specifically comprising the following steps:

s31, calculating the optimal order a of the fractional Fourier transform of the transmitting linear frequency modulation signal:

wherein f is_sIs the sampling frequency, N_sNumber of sampling points, K_rRepresenting the chirp rate;

s32, performing fractional Fourier transform on the radar echo by using the calculated optimal order a:

wherein, K_α(t, u) is the kernel function, α ═ a π/2, S_r(t) represents a radar echo signal;

s33, and for the obtained S_α(u) intoAnd searching for the maximum value, and determining the position of the maximum value, which is the position of the interference signal in the fractional domain and lags behind the position of the target signal (K)_rT_wN_s/2f_s)sin(2π-α)-cos(2π-α)T_IFurther determining the position of the target signal in the fractional domain;

s34, constructing a narrow-band filter for the position of the target signal in the fractional domain, and dividing S_α(u) inputting the signal into the narrow-band filter for filtering, and realizing the filtering of interference and the reservation of the position of a target signal;

and S35, performing fractional Fourier inverse transformation on the filtered signal to obtain a time domain signal after interference suppression.

The method has the advantages that aiming at the condition that the radar transmitting signal is in the form of the linear frequency modulation signal, the fractional Fourier transform algorithm and the segmentation idea are applied to the intermittent sampling and forwarding processing to obtain the estimation result of the key parameters of the intermittent sampling and forwarding interference of the number of the slices, the forwarding times and the width of the slices, in addition, the method can still obtain a better processing result under the condition of larger noise, and the accuracy of the identified parameters is ensured; according to the distribution characteristics of the processing result peak value pulse and the identified parameters, the detailed identification of the interference specific forwarding strategy can be realized; by adopting the fractional Fourier transform filtering technology of the linear frequency modulation signals, the interference signals can be filtered, the target signals are reserved, and simultaneously, the noise is removed, so that the countermeasure of the intermittent sampling forwarding interference is realized.

Drawings

FIG. 1 is a schematic flow chart of parameter identification according to the present invention;

FIG. 2 is a partial fractional Fourier transform processing result of intermittent sampling direct forwarding interference;

FIG. 3 is a partial fractional Fourier transform processing result of intermittent sampling repeated forwarding interference;

FIG. 4 is a partial fractional Fourier transform processing result of intermittent sampling cyclic forwarding interference;

FIG. 5 is a result of a fractional Fourier transform of an interference signal and a target signal;

fig. 6 shows the result after the interference suppression processing.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

In the embodiment, based on fractional order Fourier transform, the radar echo signals are spliced after being subjected to truncation optimal order fractional order transform, and then parameter estimation is carried out according to a processing result; according to the processing result of parameter estimation, combining the distribution characteristics of different strategies to carry out fine identification on the interference strategies; and determining the interference position according to the characteristic difference of the distribution positions of the interference and the target in the fractional order domain, and constructing a narrow-band filter for interference filtering to realize interference suppression.