I have read some reference and do simulation. But I can't get a
convergence
result. I attach my m-file programme and data. Who can tell me what
the
problem with my programme?


clc;
clear all;
close all;

fs=20; %fixed sample frequency of receiver
Ts=1/fs; %fixed sample period of receiver
fb=3; %symbol frequency
Tb=1/fb; %symbol period
Ti=Tb/2; %

%% parameter for loop filter
zeta = 0.707; % Damping factor

Wl =0.05*fb; % Lock range defined according to expected input
characteristics
Wn = Wl/2/zeta; % Natural frequency calculated from lock range

Kd = 2.27 % Phase detector gain
Ko = 1; % Loop filter gain

C1=((8*zeta*Wn*Tb)/(4+4*zeta*Wn*Tb+Wn*Wn*Tb*Tb))/(Ko*Kd);
C2=((4*Wn*Wn*Ts*Tb)/(4+4*zeta*Wn*Tb+Wn*Wn*Tb*Tb))/(Ko*Kd);


%%

x=importdata('basebandSample.txt');
figure;
plot(x);
title('waveform of baseband sample ');
hold on;
plot(x,'r*');

%%

uk=0; %fractional interval
mkDelta =floor(Ti/Ts+uk ); %increment of basepoint index

curMk=3; %current basepoint index

IdotCnt=1; %output index for interpolator
VdCnt=1; %output index for TED

demodOutCnt=1; %demod decision output index


Discriminator_Out(1)=0; %output of Gardner TED
PLL_Phase_Part(1)=0; %gain branch of loop filter
PLL_Freq_Part(1)=0; %integral branch of loop filter

Control(1)=0; %error value from loop filter

while curMk <= length(x)-1

y(IdotCnt)=(1-uk)*x(curMk)+uk*x(curMk+1); %linear interpolate


if IdotCnt>= 3 && (mod(IdotCnt ,2)==1)

Discriminator_Out(VdCnt)=y(IdotCnt-1)*[sign(y(IdotCnt))-
sign(y(IdotCnt-2))]; %Gardner TED for BPSK
%Discriminator_Out(VdCnt)=y(IdotCnt-1)*[y(IdotCnt)-
y(IdotCnt-2)];

demodOut(demodOutCnt)=y(IdotCnt);
demodOutCnt=demodOutCnt+1;

%loop filter
if VdCnt >= 2

PLL_Phase_Part(VdCnt)=Discriminator_Out(VdCnt)*C1;
Control(VdCnt)=PLL_Phase_Part(VdCnt)
+PLL_Freq_Part(VdCnt-1);

PLL_Freq_Part(VdCnt)=Discriminator_Out(VdCnt)*C2+P LL_Freq_Part(VdCnt-1);


%get next increment of basepoint and fractional interval
mkDelta=floor( Ti/Ts+ Control(VdCnt)+uk );
uk=mod( Ti/Ts+ Control(VdCnt)+uk ,1);

end

VdCnt=VdCnt+1;

end

curMk=curMk+mkDelta; %next basepoint
IdotCnt=IdotCnt+1;

end


figure;
plot(Discriminator_Out);

figure;
plot(Control);

scatterplot(x);
scatterplot(demodOut(80:length(demodOut)));