qpsk_demod.m

介绍数字通信重要的内容：调制和解调的简单实现(BPSK,QPSK,16QAM)

function output_bit=QPSK_demod(input_bit)
%input_bit(i*2)==[0,0,1,1];input_bit(i*2-1)==[0,1,0,1];
%QPSK signal mapping
%0   0   constant    constant
%0   1   -constant   constant
%1   0   constant   -constant
%1   1   -constant  -constant
L=length(input_bit);
constant=1/sqrt(2);
for i=1:L
    if real(input_bit(i))>=0
        output(i*2-1)=0;
    else
        output(i*2-1)=1;
    end
    if image(input_bit(i))>=0
        output(i*2)=0;
    else
        output(i*2)=1;
    end
end
output_bit=output;