xpol.m

此程序给出了不同情况的雷达距离测量仿真平台

% Cross Polarizes Monopulse Antenna Pattern
% -----------------------------------------

clear,clc,clf;

% Normalized Aperture Width
na=4;

% Sampling Frequeny=Number elements per norm aperture
fs=8;

% Norm aperture with N elements
N=fs*na;
xna=na*(-1/2:1/(N-1):1/2);

% Illumination Function

wxna(1:N/2)=ones(1,N/2);
wxna(N/2+1:N)=-ones(1,N/2);
wxnb(1:N/2)=ones(1,N/2);
wxnb(N/2+1:N)=ones(1,N/2);

% Fill with M/2 zeros front and back

M=1024;
xna=na*(-1/2:1/N+M-1:1/2);
wxna=[zeros(1,M/2) wxna zeros(1,M/2)];
wxnb=[zeros(1,M/2) wxnb zeros(1,M/2)];
 
% Beam Functions from -fs/2 to fs/2 in sine space

Nfft=length(wxna);
Esine=fft(wxna,Nfft);
Esine=fftshift(Esine);

Esum=fft(wxnb);
Esum=fftshift(Esum);

% Azimuth vector

sinfi=fs/4*(-Nfft/2:Nfft/2-1)/Nfft;

% Azimuth vector in radians

fi=asin(sinfi);

% Beam gain functions

Gfi= Esine.*conj(Esine)/Nfft;
Gfs=Esum.*conj(Esum)/Nfft;

Gfi(1:Nfft/2)=sqrt(Gfi(1:Nfft/2));
Gfi(Nfft/2+1:Nfft)=-sqrt(Gfi(Nfft/2+1:Nfft));
Gfs=sqrt(Gfs);

% Approximate Cross Pol Pattern

Gpc=[Gfi(1:528) -Gfi(529:1056)];

% Form Cross Pol Sum and Difference Patterns

AA=[ zeros(1,15) Gpc(1:1041)];
BB=[ Gpc(16:1056) zeros(1,15) ];

Gdif=BB-AA;
Gsum=BB+AA;

% Plot Co- and Cross Pol Paterns

subplot(2,1,1);
plot(fi,Gfs,fi,Gpc);grid;
axis([ -.25 .25 0 1 ]);
title('Co-Polarized and Cross-Polarized Patterns');
ylabel('Amplitude');
xlabel('Angle - radians');
text(.025,.9,'Co-Polarized');
text(.085,.5,'Cross-Polarized');

% Plot Co- and Cross Pol Difference Patterns

subplot(2,1,2); 
plot(fi,Gfi,fi,Gdif);grid;
axis([ -.25 .25 -1 1]);
title('Co- and Cross-Polarized Monopulse Difference Patterns');
ylabel('Amplitude');
xlabel('Angle - radians');
text(.04,.6,'Cross-Polarized');
text(-.075,.8,'Co-Polarized');