nth order filter approximations to LPF not giving proper results

Hi , i am trying to implement an analog filter Butterworth Low pass filter and want to observe the effect of order over the magnitude of that filter I have tried using the inbuilt 'butter(n,Wn,ftype)' filter but want to implement the same using the base algoritm without any inbuilt function .I have tried but not getting the proper results .

The input parameters are as follows:

Wc=pi/2.

w=(0,4*Pi) at 8pi/1000 intervals .

Thanks in advance .

[Mathieu NOE]

hello

do you have a code to share ?

Answer 1

[Harsh Kumar]

Hi Bhaskar,

I understand that you are trying to implement an analog butterworth filter with the given specifications programmatically instead of using MATLAB in-built ‘butter’ function .

You can use the fundamental mathematical strategy to implement it in MATLAB as well.

Please refer to the below code snippet for better understanding.

%frequency over which you are iterating 
w=0:8*pi/1000:4*pi;
%cutt-off frequency 
wc=pi/2;
%pre-setting to zero
H_w_2=zeros(1,length(w));
%checking for multiple orders(optional) 
for N=1:5:11   
    num=1; 
    den=zeros(1,2*N); 
    den(1)=1;
    for i=1:1:length(w)
        %implement the equation of butterworth filter 
        H_w_2(i)=1/(1+power(w(i)/wc,2*N));
        
    end
    plot(w,abs(H_w_2));
        hold on
end
legend('N=1','N=6','N=11')

[Bhaskar]

Thanks harsh, for your explanation. It cleared up my doubt and i got your approach.