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CN112014807A - An adaptive clutter suppression method for frequency agile radar - Google Patents

An adaptive clutter suppression method for frequency agile radar Download PDF

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CN112014807A
CN112014807A CN202010824214.6A CN202010824214A CN112014807A CN 112014807 A CN112014807 A CN 112014807A CN 202010824214 A CN202010824214 A CN 202010824214A CN 112014807 A CN112014807 A CN 112014807A
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clutter
clu
target
doppler
frequency
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CN112014807B (en
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曹运合
刘帅
王徐华
吴春林
罗运华
卢毅
王从思
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Xidian University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/36Means for anti-jamming, e.g. ECCM, i.e. electronic counter-counter measures
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/414Discriminating targets with respect to background clutter

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Abstract

The invention discloses a self-adaptive clutter suppression method of a frequency agile radar, which comprises the following steps: establishing a frequency agility signal model, constructing an echo data model of a frequency agility radar, and acquiring a sampling signal of a range gate where a target is located as an input signal to be processed; designing a generalized Doppler window function; designing a distance matching filter bank corresponding to the clutter Doppler channel; calculating a high-resolution one-dimensional range profile of the input signal to be processed on a clutter Doppler channel; constructing a clutter and noise covariance matrix; designing a clutter suppression filter bank corresponding to a target Doppler channel; and the clutter suppression filter bank is utilized to carry out clutter suppression and one-dimensional range profile generation on the input signal to be processed. The invention can utilize all the pulses transmitted in the frequency agile radar one-time CPI to realize clutter suppression and coherent processing, and has stronger adaptability, namely, the invention is suitable for the condition of clutter power spectrum broadening and different clutter fluctuation conditions.

Description

一种频率捷变雷达的自适应杂波抑制方法An adaptive clutter suppression method for frequency agile radar

技术领域technical field

本发明涉及雷达信号处理技术领域,具体涉及一种频率捷变雷达的自适应杂波抑制方法。适用于杂波环境下,频率捷变雷达的目标一维成像和检测。The invention relates to the technical field of radar signal processing, in particular to an adaptive clutter suppression method for a frequency agile radar. It is suitable for one-dimensional imaging and detection of targets of frequency agile radar in clutter environment.

背景技术Background technique

雷达对抗是电子对抗的一个重要组成部分,频率捷变技术是雷达实现主动抗干扰的有效措施;在频率捷变信号中,各个发射脉冲的载频以随机或者预定的方式在较宽的频带内作较大范围捷变,具备低截获概率的特性,可以有效抑制瞄准式、压制式、欺骗式等多种主幅瓣干扰形式。Radar countermeasures are an important part of electronic countermeasures. Frequency agility technology is an effective measure for radar to achieve active anti-jamming. In frequency agile signals, the carrier frequency of each transmitted pulse is randomly or predetermined in a wide frequency band. It has the characteristics of low probability of interception and can effectively suppress various forms of main lobe interference such as aiming, suppressing, and deception.

频率捷变雷达由于其优异的抗干扰和距离维高分辨能力而受到广泛关注。但由于各个脉冲发射载频的不一致,频率捷变雷达与传统的雷达动目标检测(MTD)技术不兼容,使得杂波抑制问题成为频率捷变雷达用于实际工程的一大阻碍。Frequency-agile radars have received extensive attention due to their excellent anti-jamming and range-dimensional high resolution capabilities. However, due to the inconsistency of the carrier frequencies of each pulse transmission, the frequency agile radar is incompatible with the traditional radar moving target detection (MTD) technology, which makes the clutter suppression problem a major obstacle for the frequency agile radar to be used in practical engineering.

目前适用于频率捷变雷达在杂波环境下的相参处理算法有两种。一种是先利用一次相参处理时间内的同频脉冲信号实现杂波抑制,然后再利用异频脉冲回波实现带宽合成,输出经过杂波抑制后的目标高分辨一维距离像;这种方法的缺陷在于,杂波抑制时无法利用所有脉冲提供的自由度,因此其杂波抑制性能受到限制,若要保持足够高的杂波处理增益,需要雷达发射多组同频脉冲,由此又会增加发射波形的规律性,降低频率捷变雷达的抗干扰性能。另一种方法是利用频率捷变雷达一次CPI内发射的所有脉冲实现杂波抑制和带宽合成处理,这种算法实现了异频杂波抑制,可以使用一次CPI内的所有脉冲提供的自由度实现杂波抑制,目前唯一的例子是瑞典国防研究所的S.R.J.Axelsson于2007年在IEEETrans on GRS期刊发表了subtraction算法,该算法是频率捷变雷达杂波抑制的一大进步,标志着异频杂波抑制的可行性,但该算法仅能对完全静止的杂波起到良好的抑制作用,而通常由于风速的影响,杂波的功率谱具有一定的谱宽,即杂波散射体不会是完全静止的,因此该算法在实际工程中的应用大为受限。At present, there are two kinds of coherent processing algorithms suitable for frequency agile radar in clutter environment. One is to first use the same-frequency pulse signal within a coherent processing time to achieve clutter suppression, and then use different-frequency pulse echoes to achieve bandwidth synthesis, and output a high-resolution one-dimensional range image of the target after clutter suppression; The disadvantage of this method is that the degree of freedom provided by all the pulses cannot be used in clutter suppression, so its clutter suppression performance is limited. It will increase the regularity of the transmitted waveform and reduce the anti-jamming performance of the frequency agile radar. Another method is to use all the pulses transmitted in one CPI of the frequency agile radar to achieve clutter suppression and bandwidth synthesis processing. This algorithm achieves inter-frequency clutter suppression and can be implemented using the degrees of freedom provided by all pulses in one CPI. Clutter suppression, the only example at present is that S.R.J.Axelsson of the Swedish National Defense Research Institute published the subtraction algorithm in the IEEETrans on GRS journal in 2007. This algorithm is a major advance in frequency agile radar clutter suppression, marking the difference between frequency clutter. However, the algorithm can only suppress the completely static clutter, and usually due to the influence of wind speed, the power spectrum of the clutter has a certain spectral width, that is, the clutter scatterer will not be completely static, so the application of this algorithm in practical engineering is greatly limited.

发明内容SUMMARY OF THE INVENTION

针对现有技术中存在的问题,本发明的目的在于提供一种频率捷变雷达的自适应杂波抑制方法,可利用频率捷变雷达一次CPI内发射的所有脉冲实现杂波抑制和相参处理,并且具有较强的适应性,即适用于杂波功率谱展宽的情况和不同的杂波起伏情况。In view of the problems existing in the prior art, the purpose of the present invention is to provide an adaptive clutter suppression method for a frequency agile radar, which can utilize all the pulses emitted in the primary CPI of the frequency agile radar to achieve clutter suppression and coherent processing , and has strong adaptability, that is, it is suitable for the situation of clutter power spectrum broadening and different clutter fluctuations.

为了达到上述目的,本发明采用以下技术方案予以实现。In order to achieve the above objects, the present invention adopts the following technical solutions to achieve.

一种频率捷变雷达的自适应杂波抑制方法,包括以下步骤:An adaptive clutter suppression method for frequency agile radar, comprising the following steps:

步骤1,建立频率捷变信号模型,构造频率捷变雷达在杂波背景下的回波数据模型,并对频率捷变雷达的回波数据依次进行下变频、低通滤波、脉冲压缩和目标采样,得到目标所在距离门的采样信号作为待处理输入信号;Step 1, establish a frequency agile signal model, construct the echo data model of the frequency agile radar in the clutter background, and perform down-conversion, low-pass filtering, pulse compression and target sampling on the echo data of the frequency agile radar in sequence , obtain the sampled signal of the distance gate where the target is located as the input signal to be processed;

步骤2,根据频率捷变信号模型设计广义多普勒窗函数,用于在步骤3中扩展杂波多普勒通道的多普勒覆盖范围;Step 2, design a generalized Doppler window function according to the frequency agile signal model, for extending the Doppler coverage of the clutter Doppler channel in step 3;

步骤3,根据频率捷变雷达模型设计对应于杂波多普勒通道的距离匹配滤波器组;通过该距离匹配滤波器组和所述广义多普勒窗函数,计算所述待处理输入信号在杂波多普勒通道上的高分辨一维距离像,并据此估计强杂波散射点的距离和幅度信息;Step 3, design a range-matched filter bank corresponding to the clutter Doppler channel according to the frequency agile radar model; through the range-matched filter bank and the generalized Doppler window function, calculate the input signal to be processed in the clutter. High-resolution one-dimensional range image on the wave Doppler channel, and estimate the distance and amplitude information of the strong clutter scattering point based on it;

步骤4,根据所述强杂波散射点的距离和幅度信息构造杂波加噪声协方差矩阵R;Step 4, construct a clutter-plus-noise covariance matrix R according to the distance and amplitude information of the strong clutter scattering points;

步骤5,根据频率捷变信号模型、杂波协方差矩阵R和目标的跟踪速度,设计对应于目标多普勒通道的杂波抑制滤波器组;并利用该杂波抑制滤波器组对待处理输入信号进行杂波抑制,得到杂波抑制后的目标高分辨一维距离像,完成频率捷变雷达的自适应杂波抑制。Step 5, according to the frequency agile signal model, the clutter covariance matrix R and the tracking speed of the target, design a clutter suppression filter bank corresponding to the target Doppler channel; and use the clutter suppression filter bank to input the input to be processed The signal is subjected to clutter suppression to obtain a high-resolution one-dimensional range image of the target after clutter suppression, and the adaptive clutter suppression of the frequency agile radar is completed.

与现有技术相比,本发明的有益效果为:Compared with the prior art, the beneficial effects of the present invention are:

(1)相对于利用一次相参处理时间内的同频脉冲信号实现杂波抑制的方法,本发明方法可使用所有脉冲提供的自由度来实现杂波抑制,因此具备更好的杂波抑制理论性能;由于本发明方法实现了异频杂波抑制,不需要一次相参处理时间内发射多个同频脉冲,可以保证发射信号有强随机性来降低截获概;此外,异频杂波抑制还意味着雷达可以保持在较大范围内随机捷变,不损失频率捷变雷达的高距离分辨性能。(1) Compared with the method of using the same frequency pulse signal in one coherent processing time to achieve clutter suppression, the method of the present invention can use the degrees of freedom provided by all pulses to achieve clutter suppression, so it has a better clutter suppression theory performance; because the method of the present invention realizes the suppression of inter-frequency clutter, it does not need to transmit multiple pulses of the same frequency within one coherent processing time, which can ensure that the transmitted signal has strong randomness to reduce the probability of interception; in addition, the inter-frequency clutter suppression also It means that the radar can maintain random agility in a large range without losing the high range resolution performance of frequency agile radar.

(2)与Subtraction算法相比,本发明设计了广义多普勒窗函数和杂波抑制滤波器的多普勒域展宽方法,使得本发明方法可适用于实际的杂波环境,即在杂波功率谱具有一定谱宽的情况下依然有效。(2) Compared with the Subtraction algorithm, the present invention designs the generalized Doppler window function and the Doppler domain broadening method of the clutter suppression filter, so that the method of the present invention can be applied to the actual clutter environment, that is, in the clutter environment It is still valid when the power spectrum has a certain spectral width.

附图说明Description of drawings

下面结合附图和具体实施例对本发明做进一步详细说明。The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

图1是本发明的实现流程图;Fig. 1 is the realization flow chart of the present invention;

图2(a)是本发明设计的广义多普勒窗函数的速度响应与普通矩形窗处理结果的对比图;Fig. 2 (a) is the contrast diagram of the speed response of the generalized Doppler window function designed by the present invention and the processing result of ordinary rectangular window;

图2(b)是图2(a)中3dB主瓣的局部放大图;Figure 2(b) is a partial enlarged view of the 3dB main lobe in Figure 2(a);

图3(a)是本发明中使用广义多普勒窗函数生成的对应于杂波多普勒通道的高分辨一维距离像结果图;Fig. 3 (a) is the high-resolution one-dimensional range image result map corresponding to clutter Doppler channel generated using generalized Doppler window function in the present invention;

图3(b)是使用普通矩形窗函数得到的对应于杂波多普勒通道的高分辨一维距离像结果图;Figure 3(b) is a high-resolution one-dimensional range image result corresponding to the clutter Doppler channel obtained by using an ordinary rectangular window function;

图4(a)是本发明设计的杂波抑制滤波器的距离-多普勒二维响应结果图;Fig. 4 (a) is the range-Doppler two-dimensional response result diagram of the clutter suppression filter designed by the present invention;

图4(b)是图4(a)结果中阻带的局部放大图;Fig. 4(b) is a partial enlarged view of the stop band in the result of Fig. 4(a);

图4(c)是图4(a)结果中通带的局部放大图;Fig. 4(c) is a partial enlarged view of the passband in the result of Fig. 4(a);

图5(a)是本发明设计的杂波抑制滤波器在杂波多普勒通道的距离响应结果图;Fig. 5 (a) is the range response result diagram of the clutter suppression filter designed by the present invention in the clutter Doppler channel;

图5(b)本发明实施例在通带所在距离单元的多普勒响应结果图;Fig. 5(b) Doppler response result diagram of the embodiment of the present invention in the distance unit where the passband is located;

图6(a)是使用距离匹配滤波器组得到的目标高分辨一维距离像结果图;Fig. 6 (a) is the result graph of the target high-resolution one-dimensional range image obtained using the range matched filter bank;

图6(b)是使用本发明的杂波抑制滤波器组得到的目标高分辨一维距离像结果图;Fig. 6 (b) is the result diagram of the target high-resolution one-dimensional range image obtained using the clutter suppression filter bank of the present invention;

图7(a)是本发明方法和subtraction算法随参数σc和v变化时的杂波抑制性能曲线对比图;Fig. 7 (a) is the clutter suppression performance curve comparison diagram when the method of the present invention and the subtraction algorithm change with the parameters σ c and v;

图7(b)本发明方法和subtraction算法随输入信杂噪比和参数v变化时的杂波抑制性能曲线对比图。FIG. 7(b) is a comparison diagram of the clutter suppression performance curves of the method of the present invention and the subtraction algorithm when the input signal-to-noise ratio and the parameter v change.

具体实施方式Detailed ways

下面将结合实施例对本发明的实施方案进行详细描述,但是本领域的技术人员将会理解,下列实施例仅用于说明本发明,而不应视为限制本发明的范围。The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

参考图1,本发明提供的一种频率捷变雷达的自适应杂波抑制方法,包括以下步骤:Referring to FIG. 1 , an adaptive clutter suppression method for a frequency agile radar provided by the present invention includes the following steps:

步骤1,建立频率捷变信号模型,构造频率捷变雷达在杂波背景下的回波数据模型,并对频率捷变雷达的回波数据依次进行下变频、低通滤波、脉冲压缩和目标采样,得到目标所在距离门的采样信号作为待处理输入信号;Step 1, establish a frequency agile signal model, construct the echo data model of the frequency agile radar in the clutter background, and perform down-conversion, low-pass filtering, pulse compression and target sampling on the echo data of the frequency agile radar in sequence , obtain the sampled signal of the distance gate where the target is located as the input signal to be processed;

建立频率捷变信号模型:设一次相参处理时间(CPI)内发射N个独立的线性调频脉冲,脉冲重复间隔为Tr,各个脉冲的时宽和带宽分别为Tp和Bp,频率捷变间隔为Δf,fc为初始载频,则各个脉冲的载频可分别写为fc+niΔf,其中,i=0,1,…,N-1,ni为第i个随机频率调制编码。设M为可选频点个数,则有fc+niΔf∈[fc,fc+MΔf]。那么,第i个发射脉冲信号可以写为:Establish a frequency agile signal model: suppose that N independent chirp pulses are transmitted within a coherent processing time (CPI), the pulse repetition interval is Tr , the time width and bandwidth of each pulse are T p and B p respectively, and the frequency agility The variable interval is Δf, and f c is the initial carrier frequency, then the carrier frequency of each pulse can be written as f c +n i Δf, where i=0,1,...,N-1,n i is the i-th random Frequency Modulation Coding. Let M be the number of optional frequency points, then there is f c +n i Δf∈[f c ,f c +MΔf]. Then, the i-th transmitted pulse signal can be written as:

Figure BDA0002635557960000051
Figure BDA0002635557960000051

其中,t为时间,μ=Bp/Tp为调频斜率,rect(·)是矩形窗函数,Among them, t is the time, μ=B p /T p is the frequency modulation slope, rect( ) is the rectangular window function,

Figure BDA0002635557960000052
Figure BDA0002635557960000052

构造频率捷变雷达在杂波背景下的回波数据模型:设一个径向速度为Vtar的目标被雷达捕获并跟踪,该目标由K个散射点组成,各个目标散射点与雷达之间的初始距离分别为:Rtar(1),Rtar(2),…,Rtar(K);那么,在t时刻第k个散射点相对于雷达的距离为rtar(t,k)=Rtar(k)-Vtart。Construct the echo data model of frequency agile radar in the background of clutter: set a target whose radial velocity is V tar to be captured and tracked by the radar, the target consists of K scattering points, and the distance between each target scattering point and the radar is The initial distances are: R tar (1), R tar (2),…,R tar (K); then, the distance of the kth scattering point relative to the radar at time t is r tar (t,k)=R tar (k)-V tar t.

同理,设目标所在距离门内有L个杂波散射点,各个杂波散射点与雷达之间的初始距离分别为:Rclu(1),Rclu(2),…,Rclu(L),各个杂波散射点的速度分别为:Vclu(1),Vclu(2),…,Vclu(L),那么,在t时刻第l个杂波散射点相对于雷达的距离为rclu(t,l)=Rclu(l)-Vclu(l)t。那么,对应于该距离门的接收信号可写为:Similarly, suppose that there are L clutter scattering points in the range gate where the target is located, and the initial distances between each clutter scattering point and the radar are: R clu (1), R clu (2),…,R clu (L ), the speed of each clutter scattering point is: V clu (1), V clu (2),..., V clu (L), then, the distance of the lth clutter scattering point relative to the radar at time t is r clu (t,l)=R clu (l)-V clu (l)t. Then, the received signal corresponding to this range gate can be written as:

Figure BDA0002635557960000053
Figure BDA0002635557960000053

其中,w(t)是功率为σw 2的接收机噪声,γtar(k)和γclu(l)分别是第k个目标散射点和第l个杂波散射点的散射系数。where w(t) is the receiver noise with power σ w 2 , γ tar (k) and γ clu (l) are the scattering coefficients of the k-th target scattering point and the l-th clutter scattering point, respectively.

以上接收信号经过完整的线性调频信号处理流程,即下变频,低通滤波、脉冲压缩后再进行采样处理,得到第i个回波脉冲在目标所在距离门的采样信号写为:The above received signal undergoes a complete linear frequency modulation signal processing process, that is, down-conversion, low-pass filtering, and pulse compression before sampling processing, and the sampling signal of the i-th echo pulse at the distance gate where the target is located is written as:

s(i)=star(i)+sclu(i)+w(i)s(i)=s tar (i)+s clu (i)+w(i)

其中in

Figure BDA0002635557960000061
Figure BDA0002635557960000061

Figure BDA0002635557960000062
Figure BDA0002635557960000062

定义接收信号向量为s∈C1×N,s=[s(0),s(1),…,s(N-1)],有Define the received signal vector as s∈C 1×N , s=[s(0),s(1),...,s(N-1)], we have

s=star+sclu+ws=s tar +s clu +w

其中,star=[star(0),star(1),…,star(N-1)]表示目标的采样向量,sclu=[sclu(0),sclu(1),…,sclu(N-1)]表示杂波的采样向量,w=[w(0),w(1),…,w(N-1)]表示噪声的采样向量。则向量s作为待处理输入信号。Among them, s tar = [s tar (0), s tar (1),..., s tar (N-1)] represents the sampling vector of the target, s clu = [s clu (0), s clu (1), ...,s clu (N-1)] represents the sampling vector of clutter, and w=[w(0),w(1),...,w(N-1)] represents the sampling vector of noise. Then the vector s is used as the input signal to be processed.

步骤2,根据频率捷变信号模型设计广义多普勒窗函数,用于在步骤3中扩展杂波多普勒通道的多普勒覆盖范围;Step 2, design a generalized Doppler window function according to the frequency agile signal model, for extending the Doppler coverage of the clutter Doppler channel in step 3;

广义多普勒窗函数用于展宽零多普勒通道的多普勒覆盖范围,根据频率捷变雷达回波模型中的目标采样数据的多普勒相位项,设计广义多普勒窗函数。由目标采样数据(star(i)的公式),设计一个速度为V0的杂波散射点对应的多普勒相位向量:The generalized Doppler window function is used to widen the Doppler coverage of the zero-Doppler channel. The generalized Doppler window function is designed according to the Doppler phase term of the target sampled data in the frequency-agile radar echo model. From the target sampled data (formula of s tar (i)), design a Doppler phase vector corresponding to the clutter scattering point with velocity V 0 :

Figure BDA0002635557960000063
Figure BDA0002635557960000063

同时,设计一个速度为V1的参考向量:At the same time, design a reference vector with velocity V 1 :

Figure BDA0002635557960000064
Figure BDA0002635557960000064

设广义多普勒窗函数为ω=[ω(0),ω(1),…,ω(N-1)],在使用该广义多普勒窗函数的基础上将杂波多普勒相位向量与参考向量进行互相关,得到两者的相关函数:Let the generalized Doppler window function be ω=[ω(0),ω(1),...,ω(N-1)], and on the basis of using the generalized Doppler window function, the clutter Doppler phase vector Cross-correlate with the reference vector to get the correlation function of the two:

Figure BDA0002635557960000071
Figure BDA0002635557960000071

其中,ΔV=V0-V1,⊙表示Hadamard积,[·]H表示共轭转置。Among them, ΔV=V 0 −V 1 , ⊙ represents the Hadamard product, and [·] H represents the conjugate transpose.

根据相关函数表示形式,基于传统窗函数设计广义多普勒窗函数。According to the representation of the correlation function, the generalized Doppler window function is designed based on the traditional window function.

由于广义多普勒窗函数用于展宽零多普勒通道的多普勒覆盖范围,该函数适宜基于大主瓣宽度窗函数进行设计,例如Blackman窗、Kaiser窗等等。示例性地,原始布莱克曼窗函数(Blackman窗)为:Since the generalized Doppler window function is used to widen the Doppler coverage of the zero-Doppler channel, the function is suitable to be designed based on a large main lobe width window function, such as Blackman window, Kaiser window and so on. Exemplarily, the original Blackman window function (Blackman window) is:

Figure BDA0002635557960000072
Figure BDA0002635557960000072

基于Blackman窗设计的广义多普勒窗函数可写为:The generalized Doppler window function based on Blackman window design can be written as:

Figure BDA0002635557960000073
Figure BDA0002635557960000073

步骤3,根据频率捷变信号模型设计对应于杂波多普勒通道的距离匹配滤波器组;通过该距离匹配滤波器组和所述广义多普勒窗函数,计算所述待处理输入信号在杂波多普勒通道上的高分辨一维距离像,并据此估计强杂波散射点的距离和幅度信息;Step 3, according to the frequency agile signal model, design the distance matched filter bank corresponding to the clutter Doppler channel; through the distance matched filter bank and the generalized Doppler window function, calculate the input signal to be processed in the clutter. High-resolution one-dimensional range image on the wave Doppler channel, and estimate the distance and amplitude information of the strong clutter scattering point based on it;

本发明通过生成对应于杂波多普勒通道的高分辨一维距离像来估计强杂波散射点的距离和幅度信息,以实现自适应杂波抑制。The present invention estimates the distance and amplitude information of strong clutter scattering points by generating a high-resolution one-dimensional range image corresponding to the clutter Doppler channel, so as to realize adaptive clutter suppression.

具体地,定义对应于中心速度为V的多普勒通道的距离匹配滤波器矩阵为ΦV∈CN ×M,其中

Figure BDA0002635557960000074
Figure BDA0002635557960000075
根据匹配滤波原理可知,距离匹配滤波器矩阵中的元素为:Specifically, the range-matched filter matrix corresponding to the Doppler channel whose center velocity is V is defined as Φ V ∈ C N ×M , where
Figure BDA0002635557960000074
Figure BDA0002635557960000075
According to the matched filtering principle, the elements in the distance matched filter matrix are:

Figure BDA0002635557960000081
Figure BDA0002635557960000081

由于杂波功率谱通常服从0均值高斯分布,定义Φ0为对应于杂波多普勒通道的距离匹配滤波器矩阵,其对应的中心速度为0m/s;接收信号向量s在该多普勒通道上生成的复高分辨一维距离像按如下公式计算:Since the clutter power spectrum usually obeys the 0-mean Gaussian distribution, Φ 0 is defined as the distance-matched filter matrix corresponding to the clutter Doppler channel, and its corresponding center velocity is 0 m/s; the received signal vector s is in the Doppler channel. The complex high-resolution one-dimensional distance image generated above is calculated according to the following formula:

Figure BDA0002635557960000082
Figure BDA0002635557960000082

则yclu对应的高分辨一维距离像为

Figure BDA00026355579600000810
|·|为取模操作。Then the high-resolution one-dimensional distance image corresponding to y clu is
Figure BDA00026355579600000810
|·| is the modulo operation.

对高分辨一维距离像

Figure BDA0002635557960000083
进行门限检测,超过预设检测门限的杂波散射点为强杂波散射点,得到H个强杂波散射点,则第h个强杂波散射点的距离和散射系数估计值分别为
Figure BDA0002635557960000084
Figure BDA0002635557960000085
h=1,2,…,H,H>1。For high-resolution one-dimensional range images
Figure BDA0002635557960000083
Perform threshold detection, the clutter scattering points exceeding the preset detection threshold are strong clutter scattering points, and H strong clutter scattering points are obtained, then the distance and the estimated value of the scattering coefficient of the h-th strong clutter scattering point are respectively
Figure BDA0002635557960000084
and
Figure BDA0002635557960000085
h=1,2,...,H,H>1.

步骤4,根据所述强杂波散射点的距离和幅度信息构造杂波加噪声协方差矩阵R;Step 4, construct a clutter-plus-noise covariance matrix R according to the distance and amplitude information of the strong clutter scattering points;

杂波加噪声协方差矩阵用于使得杂波抑制滤波器在强杂波散射点位置处形成零陷,考虑到杂波功率谱扩展以及强杂波散射点距离信息估计误差,本发明在速度-距离二维同时进行零陷展宽以保持杂波抑制的稳健性。The clutter-plus-noise covariance matrix is used to make the clutter suppression filter form a null at the position of the strong clutter scattering point. Considering the clutter power spectrum expansion and the estimation error of the distance information of the strong clutter scattering point, the present invention is in the speed- Simultaneous null broadening in distance 2D to maintain robustness of clutter suppression.

具体地,根据雷达当前的工作环境,设定杂波抑制滤波器的零陷在速度维的展宽程度为DV,在距离维的展宽程度为DR;其中DV大于杂波谱宽度σc,DR大于频率捷变雷达的距离分辨率c/2MΔf;设第h个强杂波散射点的距离参数

Figure BDA0002635557960000086
速度参数Vclu(h)~N(0,DV 2),那么,定义Rclu(h)和Vclu(h)的概率密度函数分别为
Figure BDA0002635557960000087
Figure BDA0002635557960000088
有:Specifically, according to the current working environment of the radar, the degree of broadening of the null trap of the clutter suppression filter in the velocity dimension is D V , and the degree of broadening in the distance dimension is D R ; where D V is greater than the clutter spectral width σ c , D R is greater than the range resolution c/2MΔf of the frequency agile radar; set the range parameter of the h-th strong clutter scattering point
Figure BDA0002635557960000086
Velocity parameters V clu (h)~N(0,D V 2 ), then, the probability density functions of R clu (h) and V clu (h) are defined as
Figure BDA0002635557960000087
and
Figure BDA0002635557960000088
Have:

Figure BDA0002635557960000089
Figure BDA0002635557960000089

Figure BDA0002635557960000091
Figure BDA0002635557960000091

定义对应于第h个强杂波散射点的杂波协方差矩阵为Rh∈CN×N,其第α行第β列元素为[Rh]α,β,则:Define the clutter covariance matrix corresponding to the h-th strong clutter scattering point as R h ∈ C N×N , and its elements in the α-th row and β-column are [R h ] α,β , then:

当α=β时,When α=β,

[Rh]α,β=1[R h ] α, β = 1

当α≠β时,When α≠β,

Figure BDA0002635557960000092
Figure BDA0002635557960000092

其中,nα为第α个随机频率调制编码,nβ为第β个随机频率调制编码;Among them, n α is the α-th random frequency modulation code, and n β is the β-th random frequency modulation code;

由于Rclu(h)和Vclu(h)彼此间具有独立性,上式可重写为:Since R clu (h) and V clu (h) are independent of each other, the above equation can be rewritten as:

Figure BDA0002635557960000093
Figure BDA0002635557960000093

基于上式可求得第h个强杂波散射点的杂波协方差矩阵Rh的每个元素。Based on the above formula, each element of the clutter covariance matrix R h of the h-th strong clutter scattering point can be obtained.

那么,定义杂波加噪声协方差矩阵为R∈CN×N,有:Then, define the clutter plus noise covariance matrix as R∈C N×N , we have:

Figure BDA0002635557960000094
Figure BDA0002635557960000094

其中,

Figure BDA0002635557960000095
为第h个强杂波散射点的距离估计值,I∈CN×N是单位矩阵。in,
Figure BDA0002635557960000095
is the distance estimate of the h-th strong clutter scattering point, and I∈C N×N is the identity matrix.

步骤5,根据频率捷变信号模型、杂波协方差矩阵R和目标的跟踪速度,设计对应于目标多普勒通道的杂波抑制滤波器组;并利用该杂波抑制滤波器组对待处理输入信号进行杂波抑制,得到杂波抑制后的目标高分辨一维距离像,完成频率捷变雷达的自适应杂波抑制。Step 5, according to the frequency agile signal model, the clutter covariance matrix R and the tracking speed of the target, design a clutter suppression filter bank corresponding to the target Doppler channel; and use the clutter suppression filter bank to input the input to be processed The signal is subjected to clutter suppression to obtain a high-resolution one-dimensional range image of the target after clutter suppression, and the adaptive clutter suppression of the frequency agile radar is completed.

设目标的跟踪速度为

Figure BDA0002635557960000101
该估计值由雷达目标跟踪模块给出。对应于目标所在的多普勒通道的距离匹配滤波器矩阵为
Figure BDA0002635557960000102
Figure BDA0002635557960000103
可由步骤3中公式(I)计算得到。Let the target tracking speed be
Figure BDA0002635557960000101
This estimate is given by the radar target tracking module. The range-matched filter matrix corresponding to the Doppler channel where the target is located is
Figure BDA0002635557960000102
Figure BDA0002635557960000103
It can be calculated by formula (I) in step 3.

设该多普勒通道对应的杂波抑制滤波器矩阵为

Figure BDA0002635557960000104
Figure BDA0002635557960000105
Figure BDA0002635557960000106
通过下式计算得到:Let the clutter suppression filter matrix corresponding to the Doppler channel be
Figure BDA0002635557960000104
Figure BDA0002635557960000105
Figure BDA0002635557960000106
It is calculated by the following formula:

Figure BDA0002635557960000107
Figure BDA0002635557960000107

Figure BDA0002635557960000108
Figure BDA0002635557960000108

由拉格朗日乘子法可知:According to the Lagrange multiplier method:

Figure BDA0002635557960000109
Figure BDA0002635557960000109

利用杂波抑制滤波器矩阵

Figure BDA00026355579600001010
对待处理输入信号s进行杂波抑制,得到杂波抑制后的目标复高分辨一维距离像:Utilize the clutter suppression filter matrix
Figure BDA00026355579600001010
Perform clutter suppression on the input signal s to be processed, and obtain a complex high-resolution one-dimensional range image of the target after clutter suppression:

Figure BDA00026355579600001011
Figure BDA00026355579600001011

对其中的各个元素取模值即可得到频率捷变雷达杂波抑制后的目标高分辨一维距离像:

Figure BDA00026355579600001012
The high-resolution one-dimensional range image of the target after frequency agile radar clutter suppression can be obtained by taking the modulo value of each element:
Figure BDA00026355579600001012

本发明为实现频率捷变雷达的自适应杂波抑制,首先利用频率捷变信号回波做出对应于杂波多普勒通道的高分辨一维距离像,用于估计强杂波散射点的距离和幅度信息;考虑到实际杂波的功率谱是扩展的,即杂波径向速度在以0为中心的小范围内随机变化,本发明方法设计了广义多普勒窗函数用于在杂波距离像成像过程中扩展杂波多普勒通道的覆盖范围。其次是根据强杂波散射点的距离和幅度估计信息设计杂波加噪声协方差矩阵,并以此计算具有距离-多普勒二维特性的杂波抑制滤波器组;该协方差矩阵用于使得杂波抑制滤波器在强杂波散射点位置处(距离-多普勒二维)形成零陷,考虑到强杂波散射点距离估计误差以及功率谱扩展情况,本发明方法可通过对协方差矩阵的调整使得杂波抑制滤波器的零陷在距离和速度维进行同时展宽,以增强方法的稳健性。最后,利用杂波抑制滤波器组取代距离匹配滤波器组以得到杂波抑制后的目标高分辨一维距离像。In order to realize the adaptive clutter suppression of the frequency agile radar, the present invention first uses the frequency agile signal echo to make a high-resolution one-dimensional range image corresponding to the clutter Doppler channel, which is used to estimate the distance of the strong clutter scattering point and amplitude information; considering that the power spectrum of the actual clutter is expanded, that is, the radial velocity of the clutter changes randomly in a small range centered at 0, the method of the present invention designs a generalized Doppler window function to be used in the clutter Extends the coverage of the clutter Doppler channel during range imaging. Secondly, the clutter plus noise covariance matrix is designed according to the distance and amplitude estimation information of the strong clutter scattering points, and the clutter suppression filter bank with the two-dimensional range-Doppler characteristic is calculated based on this; the covariance matrix is used for Make the clutter suppression filter form a zero trap at the position of the strong clutter scattering point (distance-Doppler two-dimensional), taking into account the distance estimation error of the strong clutter scattering point and the power spectrum expansion, the method of the present invention can pass the coordination The adjustment of the variance matrix allows the nulls of the clutter suppression filter to be broadened simultaneously in the distance and velocity dimensions to enhance the robustness of the method. Finally, the clutter suppression filter bank is used to replace the range-matched filter bank to obtain a high-resolution one-dimensional range image of the target after clutter suppression.

本发明方法能够利用频率捷变雷达一次CPI发射的所有脉冲实现杂波抑制,并在杂波功率谱展宽的情况下依旧适用,在实现异频杂波抑制并考虑实际杂波特性的基础上解决了频率捷变与杂波抑制的兼容问题。The method of the invention can realize the clutter suppression by using all the pulses transmitted by the primary CPI of the frequency agile radar, and is still applicable in the case of widening the clutter power spectrum, on the basis of realizing the different frequency clutter suppression and considering the actual clutter characteristics Solved the compatibility problem of frequency agility and clutter suppression.

仿真实验Simulation

为了证明本发明的有效性,采用以下仿真对比试验进一步说明。In order to prove the effectiveness of the present invention, the following simulation comparison test is used to further illustrate.

(1)仿真条件:(1) Simulation conditions:

频率捷变信号的波形参数设置如下:初始频率fc=8GHz,一次CPI的发射脉冲个数N=256,可选频点个数M=128,脉冲重复间隔Tr=100us,脉冲宽度Tp=100us,脉冲带宽Bp=10MHz,频率捷变间隔Δf=10MHz,接收机噪声功率σw 2=0dB,载频调制编码ni(i=0,1,…,M-1)服从{0,1,…,M-1}上的离散均匀分布且彼此独立。在仿真2~4中,给定了一个固定的目标场景,其中目标速度为40m/s,该目标由三个散射点组成,其距离参数分别为Rtar(1)=1508m,Rtar(2)=1509m,Rtar(3)=1510m,它们的散射系数分别为γtar(1)=1dB,γtar(2)=3dB,γtar(3)=2dB。目标所在距离门中有三个强杂波散射点和若干弱杂波散射点,弱杂波回波总功率与目标回波功率一致,三个强杂波散射点的距离参数分别为Rclu(1)=1503m,Rclu(2)=1507m,Rclu(3)=1509m,其散射系数分别为γclu(1)=20dB,γclu(2)=22dB,γclu(3)=19dB,为了模拟杂波功率谱扩展情况,设置三个强杂波散射点的速度参数分别为Vclu(1)=0.169m/s,Vclu(2)=-0.028m/s,Vclu(3)=0.483m/s,在仿真5中,目标场景根据不同的场景参数随机设置。The waveform parameters of the frequency agile signal are set as follows: the initial frequency f c =8GHz, the number of transmit pulses for one CPI = 256, the number of optional frequency points M = 128, the pulse repetition interval Tr = 100us , the pulse width T p =100us, pulse bandwidth B p =10MHz, frequency agility interval Δf=10MHz, receiver noise power σ w 2 =0dB, carrier frequency modulation code ni (i=0,1,...,M-1) obeys {0 ,1,…,M-1} are discrete uniform distributions and independent of each other. In simulations 2 to 4, a fixed target scene is given, in which the target speed is 40m/s, the target consists of three scattering points, and the distance parameters are R tar (1)=1508m, R tar (2 )=1509m, R tar (3)=1510m, and their scattering coefficients are γ tar (1)=1dB, γ tar (2)=3dB, and γ tar (3)=2dB, respectively. There are three strong clutter scattering points and several weak clutter scattering points in the range gate where the target is located. The total echo power of the weak clutter is consistent with the target echo power. The distance parameters of the three strong clutter scattering points are R clu (1 ) = 1503m, R clu (2) = 1507m, R clu (3) = 1509m, the scattering coefficients are γ clu (1) = 20dB, γ clu (2) = 22dB, γ clu (3) = 19dB, respectively, in order to To simulate the expansion of the clutter power spectrum, set the velocity parameters of the three strong clutter scattering points as V clu (1)=0.169m/s, V clu (2)=-0.028m/s, V clu (3)= 0.483m/s, in simulation 5, the target scene is randomly set according to different scene parameters.

(2)仿真内容及结果:(2) Simulation content and results:

仿真1,仿真本发明方法步骤2中的广义多普勒窗函数的特性,并将结果与普通矩形窗函数进行对比,两种窗函数的多普勒响应结果如图2(a)所示,图2(b)为图2(a)中3dB主瓣的局部放大图;从图2(a)中可以看出,广义多普勒窗函数可显著增大杂波多普勒通道的速度覆盖范围,从图2(b)中可以看出,矩形窗的3dB多普勒主瓣宽度为0.60m/s,而广义多普勒窗函数则为1.04m/s。Simulation 1, simulating the characteristics of the generalized Doppler window function in step 2 of the method of the present invention, and comparing the results with the ordinary rectangular window function, the Doppler response results of the two window functions are shown in Figure 2(a), Figure 2(b) is a partial enlarged view of the 3dB main lobe in Figure 2(a); it can be seen from Figure 2(a) that the generalized Doppler window function can significantly increase the velocity coverage of the clutter Doppler channel , as can be seen from Figure 2(b), the 3dB Doppler main lobe width of the rectangular window is 0.60m/s, while the generalized Doppler window function is 1.04m/s.

仿真2,仿真本发明方法步骤3生成的对应于杂波多普勒通道的高分辨一维距离像,并将结果与使用普通矩形窗函数时进行对比;仿真结果如图3所示,其中图3(a)是使用广义多普勒窗函数得到的结果,图3(b)是使用普通矩形窗函数得到的结果。从图3(a)中可以看出,当不使用广义多普勒窗函数时,第三个强杂波散射点无法从杂波一维距离像中被检测并估计信息,继而该强杂波散射点无法有效抑制;从图3(b)中可以看出,当使用广义多普勒窗函数时,三个强杂波散射点均可被检测,其距离参数估计分别为:

Figure BDA0002635557960000121
Figure BDA0002635557960000122
散射系数估计分别为
Figure BDA0002635557960000123
Figure BDA0002635557960000124
Simulation 2, simulate the high-resolution one-dimensional range image corresponding to the clutter Doppler channel generated in step 3 of the method of the present invention, and compare the results with when using a common rectangular window function; the simulation results are shown in Figure 3, wherein Figure 3 (a) is the result obtained using the generalized Doppler window function, and Figure 3(b) is the result obtained using the ordinary rectangular window function. As can be seen from Figure 3(a), when the generalized Doppler window function is not used, the third strong clutter scattering point cannot be detected and estimated from the clutter one-dimensional range image, and then the strong clutter The scattering points cannot be effectively suppressed; it can be seen from Figure 3(b) that when the generalized Doppler window function is used, all three strong clutter scattering points can be detected, and the estimated distance parameters are:
Figure BDA0002635557960000121
Figure BDA0002635557960000122
The scattering coefficients are estimated to be
Figure BDA0002635557960000123
Figure BDA0002635557960000124

仿真3,仿真本发明方法步骤5产生的杂波抑制滤波器的距离-多普勒二维响应,仿真结果如图4(a)所示,其中,图4(b)是图4(a)结果中阻带的局部放大图,图4(c)是图4(a)结果中通带的局部放大图;从图4(a)、4(b)、4(c)中可以看出,本发明方法设计的杂波抑制滤波器具备二维特性,该杂波抑制滤波器在目标所在的多普勒通道上形成通带,在杂波所在多普勒通道上形成零陷,且零陷位置对应于各强波散射点。该杂波抑制滤波器的在杂波多普勒通道的距离响应以及在通带所在距离单元的多普勒响应结果分别如图5(a)和5(b)所示;从图5(a)、5(b)中可以看出,零陷在距离和速度维是同时展宽的,在距离维的展宽可以降低强杂波散射点距离信息估计误差引发的杂波抑制性能下降,而速度维的展宽可以应对杂波功率谱扩展带来的影响。Simulation 3, simulating the range-Doppler two-dimensional response of the clutter suppression filter generated in step 5 of the method of the present invention, the simulation result is shown in Fig. 4(a), wherein Fig. 4(b) is Fig. 4(a) The partial enlarged view of the stopband in the result, Fig. 4(c) is the partial enlarged view of the passband in the result of Fig. 4(a); it can be seen from Figs. 4(a), 4(b) and 4(c) that, The clutter suppression filter designed by the method of the present invention has two-dimensional characteristics. The clutter suppression filter forms a passband on the Doppler channel where the target is located, and forms a null trap on the Doppler channel where the clutter is located. The position corresponds to each strong wave scattering point. The range response of the clutter suppression filter in the clutter Doppler channel and the Doppler response in the range unit where the passband is located are shown in Figures 5(a) and 5(b), respectively; from Figure 5(a) , 5(b), it can be seen that the null trap is broadened in the distance and velocity dimensions at the same time, and the broadening in the distance dimension can reduce the clutter suppression performance degradation caused by the distance information estimation error of the strong clutter scattering point, while the velocity dimension The broadening can deal with the effect of spreading the clutter power spectrum.

仿真4,仿真本发明方法步骤5产生杂波抑制后的目标高分辨一维距离像,并与普通相参处理结果进行对比,仿真结果如图6所示,其中图6(a)是使用距离匹配滤波器组得到的结果,图6(b)是使用本发明的杂波抑制滤波器组得到的结果。从图6(a)中可以看出,在传统相参处理得到的一维距离像中,目标被杂波所形成的噪底所淹没;从图6(b)中可以看出,利用本发明方法设计的杂波抑制滤波器得到的一维距离像中,目标的三个散射点形成的尖峰均可见,且尖峰位置正确对应于三个目标散射点的距离参数。Simulation 4, simulating step 5 of the method of the present invention generates a high-resolution one-dimensional range image of the target after clutter suppression, and compares it with the ordinary coherent processing result. The result obtained by the matched filter bank, Fig. 6(b) is the result obtained by using the clutter suppression filter bank of the present invention. As can be seen from Fig. 6(a), in the one-dimensional range image obtained by traditional coherent processing, the target is submerged by the noise floor formed by clutter; as can be seen from Fig. 6(b), using the present invention In the one-dimensional range image obtained by the clutter suppression filter designed by the method, the peaks formed by the three scattering points of the target are all visible, and the peak positions correspond to the distance parameters of the three scattering points of the target correctly.

仿真5,仿真本发明方法在不同输入信杂噪比、不同的杂波谱宽度以及不同的杂波起伏模型下的性能,并将结果与subtraction算法进行对比;其中输入信杂比从-30dB到-10dB变化,杂波功率谱服从谱宽σc(标准差)从0到0.5m/s变化的高斯分布,不同杂波起伏模型服从尺度参数α=1,形状参数v分别为1、2、4的K分布;在各种情况下进行10000次蒙特卡洛实验,仿真结果如图7所示,在图7(a)中仿真了本发明方法随参数σc和v变化时的情况,输入信杂噪比固定为-20dB;在图7(b)仿真了本发明方法随输入信杂噪比和参数v变化时的情况,设置杂波功率谱宽度σc固定为0.22m/s。从图7(a)中可以看出,由于没有考虑杂波谱扩展的情况,Subtraction算法的性能随着杂波功率谱谱宽的增大而下降严重;而在本发明方法中,由于广义多普勒窗函数的使用,以及杂波抑制滤波器零陷在多普勒维的展宽,该方法在杂波功率谱展宽的情况下依然适用;对比图7(a)和7(b)中可以看出,不同的杂波起伏模型对算法性能也会带来一定影响,但影响很小,这是因为本发明方法采用自适应杂波抑制体制,对不同的杂波起伏模型具有适应性。Simulation 5, simulate the performance of the method of the present invention under different input signal-to-noise ratios, different clutter spectrum widths and different clutter fluctuation models, and compare the results with the subtraction algorithm; wherein the input signal-to-noise ratio is from -30dB to - 10dB change, the clutter power spectrum obeys the Gaussian distribution with the spectral width σ c (standard deviation) varying from 0 to 0.5m/s, the different clutter fluctuation models obey the scale parameter α=1, and the shape parameter v is 1, 2, 4 respectively 10,000 Monte Carlo experiments were carried out under various conditions, and the simulation results are shown in Figure 7. In Figure 7(a), the situation when the method of the present invention changes with the parameters σ c and v is simulated, and the input signal The clutter-to-noise ratio is fixed at -20dB; in Fig. 7(b), the situation when the method of the present invention changes with the input SNR and the parameter v is simulated, and the clutter power spectrum width σ c is fixed as 0.22m/s. As can be seen from Figure 7(a), since the clutter spectrum expansion is not considered, the performance of the Subtraction algorithm decreases seriously with the increase of the clutter power spectrum width; while in the method of the present invention, due to the generalized Doppler spectrum The use of the Le window function and the broadening of the zero-notch of the clutter suppression filter in the Doppler dimension are still applicable when the clutter power spectrum is broadened; It can be seen that different clutter fluctuation models will also have a certain impact on the performance of the algorithm, but the impact is small, because the method of the present invention adopts an adaptive clutter suppression system and has adaptability to different clutter fluctuation models.

虽然,本说明书中已经用一般性说明及具体实施方案对本发明作了详尽的描述,但在本发明基础上,可以对之作一些修改或改进,这对本领域技术人员而言是显而易见的。因此,在不偏离本发明精神的基础上所做的这些修改或改进,均属于本发明要求保护的范围。Although the present invention has been described in detail with general description and specific embodiments in this specification, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (8)

1. A self-adaptive clutter suppression method of a frequency agile radar is characterized by comprising the following steps:
step 1, establishing a frequency agility signal model, constructing an echo data model of a frequency agility radar under a clutter background, and sequentially performing down-conversion, low-pass filtering, pulse compression and target sampling on the echo data of the frequency agility radar to obtain a sampling signal of a range gate where a target is located as an input signal to be processed;
step 2, designing a generalized Doppler window function according to the frequency agility signal model, and expanding the Doppler coverage range of the clutter Doppler channel in the step 3;
step 3, designing a distance matching filter bank corresponding to a clutter Doppler channel according to the frequency agile radar model; calculating a high-resolution one-dimensional range profile of the input signal to be processed on a clutter Doppler channel through the range matching filter bank and the generalized Doppler window function, and estimating the range and amplitude information of a strong clutter scattering point according to the high-resolution one-dimensional range profile;
step 4, constructing a clutter and noise covariance matrix R according to the distance and amplitude information of the strong clutter scattering points;
step 5, designing a clutter suppression filter bank corresponding to a target Doppler channel according to the frequency agile signal model, the clutter covariance matrix R and the tracking speed of the target; and performing clutter suppression on the input signal to be processed by using the clutter suppression filter bank to obtain a target high-resolution one-dimensional range profile after clutter suppression, and completing the self-adaptive clutter suppression of the frequency agile radar.
2. The adaptive clutter suppression method for frequency agile radar according to claim 1, wherein the establishing a frequency agile signal model specifically comprises: setting N independent linear frequency modulation pulses to be transmitted within one-time coherent processing time, wherein the pulse repetition interval is TrThe time width and the bandwidth of each pulse are respectively TpAnd BpFrequency agile interval of Δ f, fcThe carrier frequency of each pulse is fc+niΔ f, wherein i ═ 0,1iEncoding the ith random frequency modulation;
if M is the number of selectable frequency points, f isc+niΔf∈[fc,fc+MΔf]Then, the ith transmission pulse signal is:
Figure FDA0002635557950000021
where t is time, μ ═ Bp/TpFor chirp rate, rect (-) is a rectangular window function,
Figure FDA0002635557950000022
3. the adaptive clutter suppression method for frequency agile radar according to claim 2, wherein the constructing the echo data model of the frequency agile radar in the clutter background is specifically:
first, let a radial velocity VtarThe target is captured and tracked by the radar, the target consists of K scattering points, and the initial distance between each target scattering point and the radar is respectively as follows: rtar(1),Rtar(2),...,Rtar(K) (ii) a Then, the distance of the kth scattering point with respect to the radar at time t is rtar(t,k)=Rtar(k)-Vtart;
Secondly, it is established that there is last clutter scattering point in the range gate of target place, and the initial distance between each clutter scattering point and the radar is respectively: rclu(1),Rclu(2),...,Rclu(L), the speed of each clutter scattering point is respectively as follows: vclu(1),Vclu(2),...,Vclu(L), then the distance r of the ith clutter scattering point to the radar at time tclu(t,l)=Rclu(l)-Vclu(l)t;
Finally, the received signal corresponding to the range gate where the target is located is:
Figure FDA0002635557950000023
wherein w (t) is a power of σw 2Of the receiver noise, gammatar(k) And gammaclu(l) The scattering coefficients of the kth target scattering point and the l clutter scattering point are respectively;
the sampling signal of the ith echo pulse at the range gate where the target is located is:
s(i)=star(i)+sclu(i)+w(i)
wherein
Figure FDA0002635557950000031
Figure FDA0002635557950000032
The total target sampling signal, i.e. the input signal to be processed, is then:
s=star+sclu+w
wherein s istar=[star(0),star(1),...,star(N-1)]A sample vector, s, representing the targetclu=[sclu(0),sclu(1),...,sclu(N-1)]A sampling vector representing clutter, w ═ w (0), w (1), w (N-1)]A vector of samples representing noise.
4. The adaptive clutter suppression method for frequency agile radar according to claim 2, wherein the generalized doppler window function is designed according to a frequency agile signal model, specifically:
2.1, designing a velocity V from the Doppler phase term of the target sampling data expression0The doppler phase vector corresponding to the clutter scattering point:
Figure FDA0002635557950000033
at the same time, a speed is designed to be V1Reference vector of (2):
Figure FDA0002635557950000034
2.2, the generalized doppler window function is ω ═ ω (0), ω (1),.., ω (N-1) ], and the clutter doppler phase vector and the reference vector are cross-correlated on the basis of using the generalized doppler window function to obtain a correlation function of the two:
Figure FDA0002635557950000035
wherein Δ V ═ V0-V1By [. alpha. ] representing a Hadamard product]HRepresents a conjugate transpose;
2.3, designing a generalized Doppler window function based on a traditional window function according to the representation form of the correlation function;
wherein, the traditional window function is a Blackman window function or a Kaiser window function.
5. The adaptive clutter suppression method of frequency agile radar according to claim 4, wherein the designing of the range matched filter bank of the clutter doppler channel specifically comprises:
defining a distance-matched filter matrix corresponding to the Doppler channel with a center velocity V as phiV∈CN×MWherein
Figure FDA0002635557950000041
Figure FDA0002635557950000042
According to the matched filtering principle, the elements in the distance matched filter matrix are:
Figure FDA0002635557950000043
6. the adaptive clutter suppression method of frequency agile radar according to claim 5, wherein the computing the high resolution one-dimensional range profile of the input signal to be processed on the clutter doppler channel and estimating the range and amplitude information of the strong clutter scattering point according to the computed high resolution one-dimensional range profile is specifically:
first, due to clutter powerThe spectra are usually obeyed to a 0-mean Gaussian distribution, defining phi0A distance matching filter matrix corresponding to the clutter Doppler channel, wherein the corresponding central speed is 0 m/s; the complex high-resolution one-dimensional range profile generated by the target sampling data s on the clutter Doppler channel is calculated according to the following formula:
Figure FDA0002635557950000044
then y iscluCorresponding high resolution one-dimensional range profile is
Figure FDA0002635557950000045
| · | is the modulo operation;
then, for the high resolution one-dimensional range profile
Figure FDA0002635557950000046
Performing threshold detection, wherein clutter scattering points exceeding a preset detection threshold are strong clutter scattering points to obtain H strong clutter scattering points, and the distance and scattering coefficient estimation values of the H strong clutter scattering points are respectively
Figure FDA0002635557950000047
And
Figure FDA0002635557950000048
7. the adaptive clutter suppression method of frequency agile radar according to claim 1, wherein said constructing a clutter plus noise covariance matrix according to the distance and amplitude information of said strong clutter scattering points comprises the steps of:
4.1 setting the broadening degree of the null of the clutter suppression filter in the velocity dimension to DVThe extent of broadening in the distance dimension is DR(ii) a Wherein DVGreater than clutter spectral width σc,DRThe distance resolution c/2 Mdelta f is larger than that of the frequency agile radar; setting the distance of the h strong clutter scattering pointParameter(s)
Figure FDA0002635557950000051
Velocity parameter Vclu(h)~N(0,DV 2) Then, define Rclu(h) And Vclu(h) Respectively is
Figure FDA0002635557950000052
And
Figure FDA0002635557950000053
comprises the following steps:
Figure FDA0002635557950000054
Figure FDA0002635557950000055
where Δ f is a frequency agile interval, fcIs an initial carrier frequency, and M is the number of selectable frequency points;
4.2 define the clutter covariance matrix corresponding to the h-th strong clutter scattering point as Rh∈CN×NThe alpha row and beta column elements are [ R ]h]α,βAnd then:
when a is equal to β, then,
[Rh]α,β=1;
when a is not equal to β,
Figure FDA0002635557950000056
wherein n isαFor the alpha random frequency modulation coding, nβEncoding the beta random frequency modulation;
due to Rclu(h) And Vclu(h) Independent of each other, the above formula can be rewritten as:
Figure FDA0002635557950000061
the clutter covariance matrix R of the h-th strong clutter scattering point can be obtained based on the formulahEach of the elements of (a);
4.3, defining a clutter and noise covariance matrix as R epsilon CN×NThe method comprises the following steps:
Figure FDA0002635557950000062
wherein,
Figure FDA0002635557950000063
is the distance estimation value of the h-th strong clutter scattering point, I belongs to CN×NIs an identity matrix, σw 2Is the noise power of the receiver.
8. The method of claim 5, wherein step 5 comprises the sub-steps of:
5.1, setting the tracking speed of the target as
Figure FDA0002635557950000064
The distance matching filter matrix corresponding to the Doppler channel where the target is located is
Figure FDA0002635557950000065
Figure FDA0002635557950000066
Can be obtained by the calculation formula of the elements in the distance matching filter matrix corresponding to the Doppler channel with the central speed V in the step 3;
5.2, setting a clutter suppression filter matrix corresponding to the Doppler channel where the target is positioned as
Figure FDA0002635557950000067
Figure FDA0002635557950000068
Figure FDA0002635557950000069
Calculated by the following formula:
Figure FDA00026355579500000610
Figure FDA00026355579500000611
the method can be obtained by a Lagrange multiplier method:
Figure FDA00026355579500000612
5.3 using clutter suppression filter matrices
Figure FDA00026355579500000613
Performing clutter suppression on an input signal s to be processed to obtain a target complex high-resolution one-dimensional range profile after clutter suppression:
Figure FDA0002635557950000071
to thetatarThe module value of each element in the method can obtain a target high-resolution one-dimensional range profile after the frequency agile radar clutter is suppressed:
Figure FDA0002635557950000072
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