fsk.m

主要用来进行MATLAB中AWGN的识别算法!

% 2fsk.m
% 
% Simulation program to build 2FSK
% All of the programs had been built successfully in MATLAB 6.5


%************************ Preparation part *****************************
NUM = 512;            % The number of FFT point
sr=1000000.0;          % Symbol rate
fc = 1000000;          % The frequency of the carrier
fs = 32000000;         % The sample rate
ml=1;                  % Number of modulation levels
br=sr.*ml;             % Bit rate (=symbol rate in this case)
nd=NUM*fc/fs;         % The number of symbols
n =fc/sr;              % The number of the carrier in a symbol
ebno=15;               % Eb/N0
IPOINT=32;             % Number of oversamples
Ts = 1/sr;             % The period of the sourse signal

t=0:1/fs:1/fc*nd*n-1/fs;    % The sample point in one carrier period
fcos = cos(2*pi*fc*t);      % cosin carrier
kf=800000;
data5(1)=0;

%*********************** Filter initialization **************************

irfn=21;                                 % Number of filter taps
alfs=0.33;                                % Rolloff factor
[xh]=hrollfcoef(irfn,IPOINT,sr,alfs,1);  % Transmitter filter coefficients

%*********************** Data generation **********************************
data=rand(1,nd)>0.5;                     % rand: built in function
%fprintf('%d',data);

%*********************** 2fsk modulation **********************************

data1=data.*2-1;
%[data2]=oversample(data1,nd,IPOINT);
[data2]=oversample(data,nd,IPOINT);%<<<<<<<<<<<<<<<<<<======================
data3=conv(data2,xh);                                %(conv: build in function)
data4=data3(irfn*IPOINT/2-1:NUM+irfn*IPOINT/2-2);    % date4 is the baseband singal of 2fsk 
data4=data4+0.3;   % <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<==================================

data5(1)=data4(1)*(1/fs);
for i=1:length(data4)-1;                              
    data5(i+1)=data5(i)+data4(i)*(1/fs);
end

modulation = cos(2*pi*fc*t+2*pi*kf*data5);                 % The modulation is the 2fsk singal

%*********************** Attenuation Calculation **************************

spow=sum(modulation.*modulation)/nd;
attn=0.5*spow*sr/br*10.^(-ebno/10);
attn=sqrt(attn);

%*********************** Add White Gaussian Noise(AWGN) *******************

inoise=randn(1,length(modulation)).*attn;
modulation=modulation+inoise;

fprintf('%f,0,\n',modulation);
%**************************fing the ampltude and phade***************************

mod_hilb=hilbert(modulation);
x=real(mod_hilb);
y=imag(mod_hilb);
z=sqrt(modulation.*modulation+y.*y) ;             % z is the amplitude
%fprintf('%f\n',z);
z_ph1=y./x;
for i=1:NUM
    if (y(i)>0)&(x(i)>0)
        z_ph(i)=atan(z_ph1(i));
    elseif (y(i)>0)&(x(i)<0)
        z_ph(i)=pi+atan(z_ph1(i));
    elseif (y(i)<0)&(x(i)<0)
        z_ph(i)=pi+atan(z_ph1(i));
    elseif (y(i)<0)&(x(i)>0)
        z_ph(i)=2*pi+atan(z_ph1(i));
    elseif (y(i)>0)&(x(i)==0)
        z_ph(i)=0.5*pi;
    elseif (y(i)<0)&(x(i)==0)
        z_ph(i)=1.5*pi;
    end                      %  z_ph is the phase
end
%*************************compute the rmax********************************

a=sum(z);
ma=a/NUM;

for i=1:length(z) 
  an(i)=z(i)./ma;
  an(i)=an(i)-1;
  an(i)=an(i)*an(i);
end
  y1=fft(an,NUM);
  yxk=abs(y1(1:NUM/2));
  
 for i=1:NUM/2
    for j=1:NUM/2-i
        t=yxk(j);yxk(j)=yxk(j+1);yxk(j+1)=t;
    end
end
max=yxk(NUM/2)/NUM;
%fprintf('\nmax=%f',max);