?? carrier_x4b.m
字號:
% QPSK Demod Test
load c:\qpsk\lecroy_1.dir\sc1000.dat;
offset=1;
size=1024*4;
wave=sc1000';
fs=1e9;
% Display wave form
%plot(wave(1:100));
%grid
%title('IF Signal');
%%%pause;
data=wave;
data_fft=10*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
(data(offset:offset+size-1))))));
data_fft=data_fft-max(data_fft);
nnnn=size;
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2;
plot(ff,data_fft);
title(' IF Data Spectrum Before Filtering ');
grid;
xlabel('FREQUENCY (HZ)');
ylabel('MAGNITUDE (dB) ');
pause;
axis([450e6, 500e6 -50 0]);
pause
wave2=wave.*wave;
data=wave2;
data_fft=10*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
(data(offset:offset+size-1))))));
data_fft=data_fft-max(data_fft);
nnnn=size;
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2;
plot(ff,data_fft);
title(' X2 IF Data Spectrum');
axis([0e6, 50e6 -50 0]);
grid;
xlabel('FREQUENCY (HZ)');
ylabel('MAGNITUDE (dB) ');
pause;
hold on;
wave4=wave2.*wave2;
data=wave4;
data_fft=10*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
(data(offset:offset+size-1))))));
data_fft=data_fft-max(data_fft);
nnnn=size;
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2;
plot(ff,data_fft,'r');
title(' X4 IF Data Spectrum');
axis([0e6, 50e6 -50 0]);
grid;
xlabel('FREQUENCY (HZ)');
ylabel('MAGNITUDE (dB) ');
hold off;
pause
%*********************************
% Design A Band-Pass Filter *
%*********************************
b=fir1(100,[470/500 490/500]);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs/n_decimate);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
title(' High Pass Filter After X2');
grid
%pause
if_data=filter(b,a,if_data);
plot(if_data(1000:1100));
grid;
title('IF Waveform X2');
%pause
% generate local carrier
f_lo=380e6; % carrier
t=[0:length(wave)-1]/fs;
c_sin=sin(2*pi*f_lo*t); % carrier sine;
if_data=wave.*c_cos; % down converting
% % plot spectrum;
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2;
plot(ff,data_fft);
title(' I Data Spectrum After Down Converting');
grid;
%%pause;
n_decimate=2;
if_data=decimate(if_data,2);
size=size/n_decimate;
offset=10;
%***************************
% Plot Spectrum *
%***************************
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
nnnn=nnnn/n_decimate;
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate;
plot(ff,data_fft);
axis([100e6 150e6 -10 30]);
title(' IF Data Spectrum After Decimation');
grid;
%%pause;
%************************************
% Design A Low-Pass Filter *
%************************************
f_lowpass=[ 0, 115/250, 120/250 , 1. ];
m= [ 1., 1.0 , 1e-5, 1e-5 ];
n1=80;
b=firls(n1, f_lowpass, m);
%b=fir2(n1,f_lowpass,m);
%b=fir1(n1,130/250);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs/n_decimate);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
grid
%%pause
axis([100e6 150e6 -50 0]);
title('N1=100 taps FIR low pass filter.');
%%pause
if_data=filter(b,a,if_data);
%***************************
% Plot Spectrum *
%***************************
offset=100;
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate;
plot(ff,data_fft);
axis([50e6 150e6 -50 30]);
title(' IF Data Spectrum After Low-Pass Filter');
grid;
%%pause;
%***************************
% Times 2 *
%***************************
if_data=if_data.*if_data;
%***************************
% Plot Spectrum *
%***************************
offset=100;
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate;
plot(ff,data_fft);
axis([0e6 250e6 -50 30]);
title(' IF Data Spectrum After X2');
grid;
%pause;
%*********************************
% Design A Low-Pass Filter *
%*********************************
b=fir1(15,100/250,'high');
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs/n_decimate);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
title(' High Pass Filter After X2');
grid
%pause
if_data=filter(b,a,if_data);
plot(if_data(1000:1100));
grid;
title('IF Waveform X2');
%pause
%***************************
% Times 4 *
%***************************
if_data=if_data.*if_data;
%*******************
% Generate LO *
%*******************
length_if=length(if_data);
t=[0:length_if-1]/fs*n_decimate;
f_lo=85e6;
lo_cos=cos(2*pi*f_lo*t);
%****************
% Down Convert LO
%***************
if_data=if_data.*lo_cos;
%***************************
% Plot Spectrum *
%***************************
offset=100;
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate;
plot(ff,data_fft);
axis([0e6 50e6 -100 -40]);
title(' IF Data Spectrum After X4 and Down Convertion');
grid;
%pause;
%********************
% Decimate
%********************
n_decimate=8;
if_data=decimate(if_data,2);
if_data=decimate(if_data,4);
size=size/n_decimate;
offset=10;
%***************************
% Plot Spectrum *
%***************************
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
if_data(offset:offset+size-1)))));
nnnn=nnnn/n_decimate;
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate/2;
plot(ff,data_fft);
%axis([0e6 20e6 -150 -80]);
title(' IF Data Spectrum After Decimation');
grid;
%pause;
%*********************************
% Design High-Pass Filter *
%*********************************
b=fir1(51,[1700/3125 1900/3125]);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs/n_decimate/2);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
title(' Low Pass Filter After X2');
%axis([0e6 50e6 -50 0]);
grid
%pause
if_data=filter(b,a,if_data);
plot(if_data(50:100));
grid;
title('IF Waveform X4');
%pause
%****************
% Thresholding *
%****************
length_if=length(if_data);
for i=1:length_if
if if_data(i) > 0
carrier_data(i)=1;
else carrier_data(i)=-1;
end
end
%***************************
% Plot Spectrum *
%***************************
data=carrier_data;
offset=20;
data_fft=20*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
data(offset:offset+size-1)))));
ff=-nnnn/2:nnnn/2-1;
ff=ff/nnnn*2*fs/2/n_decimate/2;
plot(ff,data_fft);
%axis([80e6 120e6 -100 -40]);
title(' Carrier Data Spectrum');
grid;
%pause;
carrier_data=filter(b,a,carrier_data);
plot(carrier_data(20:100),'*');
hold on;
plot(carrier_data(20:100));
hold off;
grid;
title('Carrier Waveform ');
%pause
% count cycle
carrier_ref=carrier_data(50:270);
length_ref=length(carrier_ref);
cycle_count=0;
for i=1:length_ref-1;
if carrier_ref(i)*carrier_ref(i+1) <=0
cycle_count=cycle_count+1;
end
end
cycle_carrier=(length_ref-1)/fs*n_decimate*2/cycle_count*2;
frequency_carrier=1/cycle_carrier;
%*******************
% Generate LO *
%*******************
length_if=length(if_data);
t=[0:length_if-1]/fs*n_decimate*2;
sin_lo=sin(2*pi*frequency_carrier*t);
carrier_data=filter(b,a,carrier_data);
plot(carrier_data(100:200));
hold on;
aaa=2;
plot(sin_lo(100+aaa:200+aaa),'r');
hold off;
grid;
title('Carrier Waveform ');
pause
for kk=1:200
iq=i_data+1i*q_data;
plot(iq(kk), '*');
axis([-1 1 -1 1]*.2);
grid
%%pause
end
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