Can someone explain why the error and filtered signals are switching alternatively.

Hello,

I have been working out from a longtime on adaptive filtering with leastmean square method but was unable to get the right way for the LMS implementation.

I implemented the following considering each pulse signal has 500 samples.For the first pulse signal(of 500 samples)the reference signal is generated from the lowpass filter of the pulse signal and then using the generated error as reference noise signal for the next pulse signals

P=load('Pulse_signal.mat');
a2=P.a(334:4500,:);
for i=1:500:length(a2)-500   
    if(i<500)
        input=a2(i:i+499,:); 
        detected(i:i+499,:)=input; 

          d = fdesign.lowpass('Fp,Fst,Ap,Ast',1.5,8,0.5,20,500);
          Hd1 = design(d);
          filtered = filtfilt(Hd1.Numerator,1,input);              
          [w,y,e,W]=simple_LMS1(filtered,input,0.08,5);   

          e2(i:i+499,:)=e;      
          y2(i:i+499,:)= y;

      else        
          input=a2(i:i+499,:);  
          detected(i:i+499,:)=input; 

          [w,y,e,W]=simple_LMS1(e,input,0.08,8);         

          e2(i:i+499,:)=e;
          y2(i:i+499,:)= y;               
      end;
  end
  plot(detected);hold on;plot(e2,'-r');hold on;plot(y2,'-k');

simple_LMS1 fucntion

function [w,y,e,W] = simple_LMS1(x,d,mu_step,M)
N = length(x);
 y = zeros(N,1); 
 w = zeros(M,1); 
e = zeros(N,1); 
W = zeros(M,N); 
for n = 1:N
  if n <= M % assume zero-samples for delayed data that isn't available
      k = n:-1:1;
      x1 = [x(k); zeros(M-numel(k),1)];
  else
      x1 = x(n:-1:n-M+1); % M samples of x in reverse order
  end
  y(n) = w'*x1; 
  e(n) = d(n) - y(n); 
  w = w + mu_step*e(n)'*x1;
  W(:,n) = w; 
end

Problem: But the problem is that the output(more or less similar to input) is being alternatively shifted between the error signal and filtered signal as shown in the image below.

 Can I know why this is happening.

Answer 1

[Gova ReDDy]

Can someone explain why the error and filtered are switching alternatively after each iteration. Is there something wrong with the code itself .

[Gova ReDDy]

can someone help me out in solving this mystery of alternating switching.

[Image Analyst]

Doug Hull can.

[Gova ReDDy]

Thanks and Can I know how to approach him.

[Image Analyst]

He made a video for you. Click on the link. You can always call the Mathworks if you're not getting the help you need here.

[Gova ReDDy]

Sorry, Image Analyst I didn't get you.

as he has many video tutorials here .Can I know which one are you referring to me.

[Image Analyst]

When you're using a web browser and the text switches to a different color, like blue, it means that that text is a link. You can put your arrow over that blue text and it will change into a hand. Look in my comment where I put his name. See that it is in a different color? That means it's a link to the video where Doug will tell you how to solve your problem.