modulate_21mc.m

对要发送的序列进行上变频

% 21M正交载波调制输出
function mod_21m=modulate_21Mc(reg);
reg=[0 0 0 0 0 0 0 0 0 0 0 1];
cic_seq=CIC_8(reg);
n=1:65536;

carrier_I=sin(2*pi*21*n/64);
carrier_Q=cos(2*pi*21*n/64);     % 2路正交载波

mid_freq_I=cic_seq(1,1:65536).*carrier_I;
mid_freq_Q=cic_seq(1,1:65536).*carrier_Q;  
mod_21m=mid_freq_I+mid_freq_Q;      % 2路信号经正交载波调制后相加输出

MID_FREQ_I=fft(mid_freq_I);
MID_FREQ_Q=fft(mid_freq_Q);
QAM_16_FREQ=fft(mod_21m);    % 调制信号的频谱

figure(6);
subplot(2,2,1);
stem([1:65536],mid_freq_I);axis([0 3000 -40 40]);
xlabel('n');ylabel('mid__freq__I');title('I路中频调制信号');grid;

subplot(2,2,2);
stem([1:65536],mid_freq_Q);axis([0 3000 -40 40]);
xlabel('n');ylabel('mid__freq__Q');title('Q路中频调制信号');grid;

subplot(2,2,3);
n=1:65536;
plot(2*n/65536,abs(MID_FREQ_I));axis([0.62 0.69 -50 50000]);grid;
xlabel('frequence(*pi)');ylabel('MID__FREQ__I');title('I路中频调制信号频谱');grid;

subplot(2,2,4);
n=1:65536;
plot(2*n/65536,abs(MID_FREQ_Q));axis([0.62 0.69 -50 50000]);grid;
xlabel('frequence(*pi)');ylabel('MID__FREQ__Q');title('Q路中频调制信号频谱');grid;

figure(7);
subplot(2,1,1);
stem([1:65536],mod_21m);axis([0 4000 -40 40]);
xlabel('n');ylabel('mid__freq__I');title('16QAM时域中频输出信号');grid;

subplot(2,1,2);
n=1:65536;
plot(2*n/65536,abs(QAM_16_FREQ));axis([0.62 0.69 -50 100000]);grid;
xlabel('frequence(*pi)');ylabel('QAM__16__FREQ');title('16QAM中频输出信号频谱');grid;

figure(8)
n=1:65536;
plot(2*n/65536,abs(QAM_16_FREQ));axis([0 2 -50 70000]);grid;
xlabel('frequence(*pi)');ylabel('QAM__16__FREQ');title('16QAM中频输出信号频谱');grid;