?? carrier_x4e.m
字號:
% QPSK Demod Test
clear;
load c:\qpsk\lecroy_1.dir\sc1003.dat;
%load c:\lecroy_1.dir\sc1002.dat;
wave=sc1003';
offset=1;
size=1024*4;
fs=1e9;
% Display wave form
plot(wave(1:100));
grid
title('IF Signal');
%%%%%%pause;
data_fft=10*log10(abs(fftshift(fft(kaiser(size,11.)'.*...
(wave(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 ');
axis([400e6, 500e6 -50 0]);
grid;
xlabel('FREQUENCY (HZ)');
ylabel('MAGNITUDE (dB) ');
%pause;
% generate local carrier
f_lo=(480-50)*1e6; % carrier
t=[0:length(wave)-1]/fs;
carrier_a=sin(2*pi*f_lo*t); % carrier sine;
if_data=wave.*carrier_a; % down converting
% % plot spectrum;
data=if_data;
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;
plot(ff,data_fft);
title(' I Data Spectrum After Down Converting');
grid;
%%%pause;
axis([0 100e6 -10 30]);
%%%pause;
%************************************
% Design A Low-Pass Filter *
%************************************
f_lowpass=[ 0, 65/500, 80/500 , 1. ];
m= [ 1., 1.0 , 1e-5, 1e-5 ];
n1=80;
b=firls(n1, f_lowpass, m);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
grid
%%%pause
axis([0e6 100e6 -50 0]);
title('N1=100 taps FIR low pass filter.');
%%%pause;
if_data=filter(b,a,if_data);
if_50_data=if_data;
%***************************
% Plot Spectrum *
%***************************
data=if_data;
offset=100;
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;
plot(ff,data_fft);
title(' IF Data Spectrum After Low-Pass Filter');
grid;
%%%pause;
axis([0e6 100e6 -50 30]);
%%%pause;
%***************************
% Times 2 *
%***************************
if2_data=if_data.*if_data;
%***************************
% Plot Spectrum *
%***************************
offset=100;
data=if2_data;
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;
plot(ff,data_fft);
axis([0e6 250e6 -50 30]);
title(' IF Data Spectrum After X2');
grid;
%pause;
%***************************
% Times 4 *
%***************************
if4_data=if2_data.*if2_data;
%***************************
% Plot Spectrum *
%***************************
offset=100;
data=if4_data;
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;
plot(ff,data_fft);
axis([200e6 250e6 -100 -30]);
title(' IF Data Spectrum After X4');
grid;
%pause;
%*********************************
% Design A Low-Pass Filter *
%*********************************
b=fir1(400,[213/500 220/500]);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
title(' Band-Pass Filter After X2');
axis([200e6 250e6 -50 0]);
grid
%%pause
if4_data=filter(b,a,if4_data);
plot(if4_data(1000:3100));
grid;
title('IF Waveform X4');
%%pause;
%***************************
% sign *
%***************************
if4_data=sign(if4_data);
%***************************
% Plot Spectrum *
%***************************
offset=100;
data=if4_data;
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;
plot(ff,data_fft);
%axis([200e6 250e6 -100 -30]);
title(' IF Data Spectrum After X4');
grid;
%pause;
if4_data=filter(b,a,if4_data);
plot(if4_data);
grid;
title('IF Waveform X4 After Sign 1');
%pause;
for ii=1:10
step=300;
plot(if4_data(100+(ii-1)*step:ii*step+100));
grid;
title('IF Waveform after 1 sign ');
%%pause;
end;
%***********************
% count cycle
%***********************
carrier_ref=if4_data(1000:5000-100);
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
carrier_cycle=(length_ref-1)/fs/cycle_count*2;
carrier_frequency=1/carrier_cycle;
%*******************
% Generate LO *
%*******************
length_if=length(if4_data);
t=[0:length_if-1]/fs;
sin_lo=sin(2*pi*(carrier_frequency+1e3)*t);
for ii=1:20
step=100;
plot(if4_data(500+(ii-1)*step:ii*step+500));
hold on;
aaa=5;
plot(sin_lo(500+aaa+(ii-1)*step:ii*step+500+aaa),'r');
hold off;
grid;
title('Carrier and Signal Waveform ');
pause;
end;
true_carrier_frequency=carrier_frequency/4;
%*******************
% Generate LO *
%*******************
length_wave=length(if_50_data);
t=[0:length_wave-1]/fs;
lo_cos=cos(2*pi*(true_carrier_frequency)*t);
lo_sin=sin(2*pi*(true_carrier_frequency)*t);
%************************
% Check Carrier Phase
%***********************
%for i=1:10
% step=400;
%plot(if_50_data(1+(i-1)*step:i*step)*8);
%hold on;
%aaa=-1;
%plot(lo_sin(1+aaa+(i-1)*step:i*step+aaa),'r');
%plot(lo_cos(1+aaa+(i-1)*step:i*step+aaa),'g');
%hold off;
%grid;
%title('***** Check Carrier Phase ***** ');
%%pause
%end
%****************
% Down Convert LO
%***************
i_data=if_50_data.*lo_cos;
q_data=if_50_data.*lo_sin;
%*********************************
% Design A Low-Pass Filter *
%*********************************
b=fir1(100,25/500);
a=1;
moduc=2^(-23);
%b=round(b/moduc/max(b))*moduc;
[amp,freq]=freqz(b,a,4096,fs);
amp=20*log10( (abs(amp)+1e-8) / (max(abs(amp)) +1e-8) );
plot(freq,amp);
title(' Low Pass Filter');
%axis([200e6 250e6 -50 0]);
grid
%%%pause
i_data=filter(b,a,i_data);
q_data=filter(b,a,q_data);
for i=1:4
step=500;
plot(i_data(100+(i-1)*step:100+i*step));
hold on;
plot(q_data(100+(i-1)*step:100+i*step),'r');
hold off;
grid;
title(' Demod I Data');
axis([1 500 -.1 .1]);
%pause;
end
%******************
% Timing Loop *
%******************
f_symbol=19.51e6;
n_ratio=fs/f_symbol;
iq_offset=400;
eye_max=0;
for timing_offset=0:50
n(1)=0;
n_sample=0;
for i=2:4000
n(i)=round( (i+timing_offset)/n_ratio);
if n(i) > n(i-1)+.5 % take sample;
n_sample=n_sample+1;
i_sample(n_sample)=i_data(iq_offset+i);
q_sample(n_sample)=q_data(iq_offset+i);
%[i n_sample]
%pause
end
end
eye(timing_offset+1)=sum(i_sample.^2+q_sample.^2);
if eye(timing_offset+1) > eye_max
eye_max=eye(timing_offset+1);
max_offset=timing_offset;
i_sample_out=i_sample;
q_sample_out=q_sample;
end
end
iq_sample=i_sample_out+1i*q_sample_out;
plot(iq_sample, '*');
grid
title(' Timing Adjustment');
pause;
%***************************
% correct phase error *
%***************************
ref_45=45*pi/180;
ref_135=135*pi/180;
for kk=1:n_sample-1
angle_rad=angle(iq_sample(kk));
sign_i=sign(real(iq_sample(kk)));
sign_q=sign(imag(iq_sample(kk)));
switch sign_i*2+sign_q
case 3, eye_phase_error(kk)=angle_rad-ref_45;
case -1, eye_phase_error(kk)=angle_rad-ref_135;
case -3, eye_phase_error(kk)=ref_135+angle_rad;
case 1, eye_phase_error(kk)=ref_45 +angle_rad;
otherwise '!!!! Error !!!!';
end
end
phase_correction=mean(eye_phase_error);
phase_shift=cos(phase_correction)-1i*sin(phase_correction);
iq_sample= iq_sample*phase_shift;
plot(iq_sample, '*');
grid
title(' Timing Adjustment');
pause;
%*************
% second phase
%*************
for kk=1:n_sample-1
angle_rad=angle(iq_sample(kk));
sign_i=sign(real(iq_sample(kk)));
sign_q=sign(imag(iq_sample(kk)));
switch sign_i*2+sign_q
case 3, eye_phase_error(kk)=angle_rad-ref_45;
case -1, eye_phase_error(kk)=angle_rad-ref_135;
case -3, eye_phase_error(kk)=ref_135+angle_rad;
case 1, eye_phase_error(kk)=ref_45 +angle_rad;
otherwise '!!!! Error !!!!';
end
end
phase_correction=mean(eye_phase_error);
phase_shift=cos(phase_correction)-1i*sin(phase_correction);
iq_sample= iq_sample*phase_shift;
plot(iq_sample, '*');
grid
title(' Phase Adjustment II');
pause;
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