bpsk(x,fc,fs,br)

function bpsk(x,fc,fs,br)
%x is received signal input file usually *.mat file
%fc is carrier frequency in Hz
%fs is sampling frequency in Hz
%br is bitrate in Hz
%the command should be like this:
%load input file
%then type bpsk(x,1000,8000,100) in command window
%means that x is the input, fc=1000Hz, fs=8000Hz, bitrate=100Hz
%Author: Mohamad Zuhairi Ismail
%UTM Skudai, Malaysia
[e-mail]
onebit=fs/br; %number of samples per bit
n=(length(x)-1)/onebit; %number of bits transmitted
b=onebit;
c=1;
k=[];

for m=1:n; %iteration from 1 to number of bits
y=x(c:b); % take the needed signal for one bit
q=cos(2*pi*((c:b)-1)*fc/fs); %reference signal for Quadrature
i=-cos(2*pi*((c:b)-1)*fc/fs); %reference signal for Inphase
a=y.*q; % (received signal) . (reference signal for Quadrature)
d=y.*i; % (received signal) . (reference signal for Inphase)
t= sum(a)-sum(d); %constellation
if t>0;
    p=ones(1,onebit); %create output (1) for the length of one bit
else
    p=zeros(1,onebit); %create output (0) for the length of one bit
end

k=[k p]; %accumulate the value of output into k
b=b+onebit; %update the value of b for the next input
c=c+onebit; %update the value of c for the next input
end
subplot(2,1,1); plot(x);grid on; %plot the input signal on the same graph
axis([0 n*onebit -1.5 1.5]); % specify the height and the witdh of the axis
subplot(2,1,2);plot(k,'LineWidth',1.5);grid on; %plot the output (bpsk signal)
axis([0 n*onebit -0.5 1.5]);