twtserro.m

此程序给出了不同情况的雷达距离测量仿真平台

 % TWT Serrodyning With Offset
% ---------------------------------

clf;clc;clear;

% Set Input Parameters

r=.02;	% Ratio T2/T1+T2
N=128;	% Sample Points

% Define time vector 0 to tmax

T2=r/(1-r);
tmax=1+T2;
t=tmax*(0:N-1)/N;

% Sample frequency fs

fs=N/tmax;

% Define ramp z which runs from
% 0 to T1=1 with amplitude 1 and
% flyback from t=1 to t=1+T2

for k=1:N;
if t(k)<=1;z(k)=t(k);
else z(k)=1-(t(k)-1)/T2;end;
end;

% Plot Serrodyne Waveform

t1=tmax*(0:N)/N;
zz=z;
zz(N+1)=0;

subplot(211);
plot(t1,zz);grid;
xlabel('Time - sec');
ylabel('Amplitude');
title(['Serrodyne Waveform']);


% Define Phase Modulated Signal

j=sqrt(-1);
fo=0;
x=exp(j*2*pi*(fo*t+z));


% Find x for M steps

M=64;A=[];
for m=1:M;
A=[A x];end;
x=A;

% Extend for t vector

N=N*M;
t=tmax*(0:N-1)/N;

% Spectrum for x(t)

X=fft(x);
Px=X.*conj(X);
Px=fftshift(Px);

% Select central frequency axis

Px(3*N/4+1:N)=[];
Px(1:N/4)=[];
fax=fs*(-N/4:N/4-1)/N;

% Normalize amplitude

Px=Px/max(Px);
Pxdbm=10*log10(Px+1e-6);

subplot(212);
plot(fax,Pxdbm);grid;
xlabel('Frequency - Hz');ylabel('Amplitude - db');
title(['TWT Serrodyne Spectrum' ...
'    (Flyback Ratio =',num2str(r),')']);
axis([-30 30 -40 0]);