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摘要
旁瓣对消（Ｓｉｄｅｌｏｂｅ Ｃａｎｃｅｌｌａｔｉｏｎ，ＳＬＣ）作为雷达抗干扰的重要措施之一，在电子对抗中起着重要的作用。为了深入分析不同参量对旁瓣对消性能的影响，越来越多的学者开展旁瓣对消技术研究并根据研究结果进行ＳＬＣ 系统改进或研究攻击旁瓣对消系统薄弱环节的新型干扰技术。目前，研究主要针对干扰个数、干扰形式、辅助阵元位置、通道一致性等因素对旁瓣对消系统性能的影响，而分析多干扰角度分布对旁瓣对消系统性能影响的较少。
引言
现代电子战战场环境越来越复杂，雷达在工作的同时受到各种有意或无意的干扰。为提高雷达的抗干扰性能，雷达采取各种抗干扰措施，旁瓣对消（Ｓｉｄｅｌｏｂｅ Ｃａｎｃｅｌｌａｔｉｏｎ，ＳＬＣ）作为雷达最重要的抗干扰手段之一，可大大削弱旁瓣干扰对雷达性能的影响。但旁瓣对消的性能受多方因素影响，如辅助阵元位置、干扰类型、干扰个数、干扰角度等。文献［１］分析了干扰个数对ＳＬＣ 系统对消性能的影响，提出饱和干扰概念；文献［２］分析了辅助单元位置对ＳＬＣ 系统对消性能的影响；文献［３］分析了通道失配对ＳＬＣ 对消性能的影响；文献［４］分析了信号相关性对ＳＬＣ 对消性能的影响；文献［５］分析了干扰入射角度和目标入射角度对ＳＬＣ 对消性能的影响，涉及的干扰角度主要是单干扰情况；文献［６］分析了饱和干扰时多干扰角度分布对ＳＬＣ 对消性能的影响，提出饱和多机干扰部署方式，但并未分析非饱和时干扰角度分布对ＳＬＣ 对消性能的影响。
旁瓣对消抑制比理论模型
MATLAB仿真结果
clc;close all;clear all;global c;global j;c = 3e8; %光速m/sj = sqrt(-1); %虚数%% 雷达参数radarpara.PRT = 1000e-6; %周期sradarpara.Tao = 40e-6; %脉冲持续时间 脉宽sradarpara.B = 5e6; %信号带宽Hzradarpara.Kr = radarpara.B/radarpara.Tao; %线性调频率radarpara.Fs = 2*radarpara.B; %距离采样频率24MHz，2为过采样率radarpara.Ts = 1/radarpara.Fs; %距离采样时间间隔sradarpara.f0 = 3e9; %雷达工作频率Hzradarpara.lamda = c/radarpara.f0; %雷达工作波长mradarpara.dx = 0.05; %横向单元间距radarpara.dy = 0.05; %纵向单元间距radarpara.Nx = 40; %横向单元数radarpara.Ny = 40; %纵向单元数radarpara.Nx_main = 1:radarpara.Nx;radarpara.Ny_main = 1:radarpara.Ny;radarpara.Nx_slc = 11:18;radarpara.Ny_slc = 11:18;radarpara.azi = 0;radarpara.ele = 0;radarpara.num_slc = 1;radarpara.azi_slc = zeros(radarpara.num_slc,1);radarpara.ele_slc = zeros(radarpara.num_slc,1);radarpara.azi_slc = [4 ];radarpara.ele_slc = [4 ];%ctrl.Bomen_st = max([60e3,radarpara.Tao*1e6*150]); %波门起始距离ctrl.Bomen_end = min([150e3,radarpara.PRT*1e6*150]); %波门结束距离ctrl.N = ceil(2 * (ctrl.Bomen_end-ctrl.Bomen_st) / c / radarpara.Ts); %A/D后总点数%% 回波target.R0 = 100e3; %目标中心斜距mtarget.Azi = radarpara.azi;target.Ele = radarpara.ele;false_target.R0 = 110e3; %假目标中心斜距mfalse_target.Azi = target.Azi;false_target.Ele = target.Ele;noise = randn(1,ctrl.N).*exp(j*randn(1,ctrl.N));echo = noise;Nst = floor(2*(target.R0-ctrl.Bomen_st) /c / radarpara.Ts) +1;Ned = floor((2*(target.R0-ctrl.Bomen_st) /c + radarpara.Tao)/ radarpara.Ts) +1;Ned = min([Ned,ctrl.N]);t = (1:ctrl.N)*radarpara.Ts+ctrl.Bomen_st/150*1e-6;r = t*1e6*150;ts = (Nst:Ned)*radarpara.Ts;phrase = 1/2*radarpara.Kr*ts.^2;B = 0 ;for row = 1:length(radarpara.Nx_main)for col = 1:length(radarpara.Nx_main)fai = (radarpara.Nx_main(row)-1)*radarpara.dx*sind(target.Azi) + (radarpara.Nx_main(col)-1)*radarpara.dy*sind(target.Ele);B = B + exp(-j*2*pi*fai/radarpara.lamda);endendtarget1 = B;echo(Nst:Ned) = echo(Nst:Ned) + target1*exp(j*2*pi*phrase);%副瓣干扰Jam.azi1 = radarpara.azi_slc(1);Jam.ele1 = radarpara.ele_slc(1);Jam.f1 = radarpara.f0;B = 0 ;for row = 1:length(radarpara.Nx_main)for col = 1:length(radarpara.Nx_main)fai = (radarpara.Nx_main(row)-1)*radarpara.dx*sind(Jam.azi1) + (radarpara.Nx_main(col)-1)*radarpara.dy*sind(Jam.ele1);B = B + exp(-j*2*pi*fai/radarpara.lamda);endendtarget2 = B;Nst2 = floor(2*(false_target.R0-ctrl.Bomen_st) /c / radarpara.Ts) +1;Ned2 = floor((2*(false_target.R0-ctrl.Bomen_st) /c + radarpara.Tao)/ radarpara.Ts) +1;Ned2 = min([Ned2,ctrl.N]);ts2 = (Nst2:Ned2)*radarpara.Ts;phrase2 = 1/2*radarpara.Kr*ts2.^2;echo(Nst2:Ned2) = echo(Nst2:Ned2) + target2*exp(j*2*pi*phrase2);figure;subplot(3,1,1)plot(r/1e3,db(abs(echo)),'.-');grid;xlabel('R/km');ylabel('幅度/dB');title('主通道信号');%对消通道B = 0;for row = 1:length(radarpara.Nx_slc)for col = 1:length(radarpara.Ny_slc)fai = (radarpara.Nx_slc(row)-1)*radarpara.dx*sind(Jam.azi1) + (radarpara.Ny_slc(col)-1)*radarpara.dy*sind(Jam.ele1);B = B + exp(-j*2*pi*fai/radarpara.lamda);endendtarget3 = B;noise = randn(1,ctrl.N).*exp(j*randn(1,ctrl.N));echo_slc(1,:) = noise;echo_slc(1,Nst2:Ned2) = echo_slc(1,Nst2:Ned2) + target3*exp(j*2*pi*phrase2);subplot(3,1,2)plot(r/1e3,db(abs(echo_slc(1,:))),'.-');grid;xlabel('R/km');ylabel('幅度/dB');title('对消通道信号');noise = randn(1,ctrl.N).*exp(j*randn(1,ctrl.N));echo_slc(2,:) = noise;echo_slc(2,Nst2:Ned2) = echo_slc(2,Nst2:Ned2) + target3*exp(j*2*pi*phrase2);subplot(3,1,3)plot(r/1e3,db(abs(echo_slc(2,:))),'.-');grid;xlabel('R/km');ylabel('幅度/dB');title('对消通道信号2');figure;subplot(2,1,1)plot(Nst:Ned,angle(echo(Nst:Ned)),'.-');grid;subplot(2,1,2)plot(Nst:Ned,angle(echo_slc(Nst:Ned)),'.-');grid;angle_var = angle(echo(Nst:Ned))- angle(echo_slc(Nst:Ned));index = find(angle_var < 2*pi);angle_var(index) = angle_var(index) + 2*pi;index = find(angle_var > 2*pi);angle_var(index) = angle_var(index) - 2*pi;figure;plot(1:Ned-Nst+1,angle_var,'.');grid;angle_var = angle(echo(Nst2:Ned))- angle(echo_slc(Nst2:Ned));index = find(angle_var < 2*pi);angle_var(index) = angle_var(index) + 2*pi;index = find(angle_var > 2*pi);angle_var(index) = angle_var(index) - 2*pi;figure;plot(1:length(angle_var),angle_var,'.');grid;result_slc = slc(radarpara,ctrl,echo,echo_slc);%对消function result_slc = slc(radarpara,ctrl,echo,echo_slc)num_slc = size(echo_slc,1);%对消波束个数%选干扰样本R_starts = 1:128:length(echo);Result = zeros(num_slc,length(R_starts)-1,1);for j = 1:num_slcfor i = 1:length(R_starts)-1Rx = R_starts(i):R_starts(i+1)-1;Result(j,i) = abs( echo(1,Rx)*echo_slc(j,Rx)' )./(norm(echo(1,Rx))*norm(echo_slc(j,Rx)));endendResult1 = max(Result,[],1);index_slc = find(Result1 > 0.5);r = ctrl.Bomen_st + R_starts(1:end-1)*radarpara.Ts*1e6*150;r = r/1e3;figure;plot(r,Result,'.-');grid;xlabel('R/km');ylim([-1,2]);title('副瓣对消选样本');%计算权值W = 0;for i = 1:length(index_slc)Rx = R_starts(index_slc(i)):R_starts(index_slc(i)+1)-1;sample_echo = echo(1,Rx);sample_echo_slc = echo_slc(1,Rx);W = W + sum(sample_echo.*sample_echo_slc)/length(sample_echo) * inv(sum(sample_echo_slc.*sample_echo_slc)/length(sample_echo));endW = W/length(index_slc);% index = 13280;% W = echo(1,index)*echo_slc(1,index) * inv(echo_slc(1,index)*echo_slc(1,index));%副瓣对消% Ryy = echo_slc*echo_slc'/length(echo_slc);% Rxy = echo*echo_slc'/length(echo);% result_slc = echo - abs(Rxy)^2*inv(Rxy)/Ryy*echo_slc;result_slc = echo - W*echo_slc;t = (1:ctrl.N)*radarpara.Ts+ctrl.Bomen_st/150*1e-6;r = t*1e6*150;figure;plot(r/1e3,db(abs(result_slc)),'.-');grid;ylim([-20,80]);end
参考文献
雷达旁瓣对消系统角度敏感性分析
