# How to design a FIR Filter

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Ramesh Vukyam on 1 Apr 2012
Answered: Tina on 22 Dec 2019
Hello, I am new to matlab. I want to design FIR,Butterworth and some RC filters in Matlab with GUIDE. Someone told me that I can design it using Signal Processing Toolbox. Is it possible to implement these filters without any toolboxes otherthan just matlab and GUIDE.

Wayne King on 1 Apr 2012
Yes, it is possible, but you will have to write a lot of code. The Signal Processing Toolbox (SPT) enables you to create these filters easily. Filter design code can be very complicated, so you will have to invest a lot of time to do it without SPT.

Tina on 22 Dec 2019
not sure about rc filter but FIR and butterworth filter can be designed by the help of built in function fir1,Filter.
b = fir1(48,wc);
freqz(b,1,512)
for butterworth you use butter(L).
n=%order of filter
fs=%sampling frequency
wc=fc/(fs/2);%cuttoff freq of filter
b=fir1(n,wc,'low',butter(n+1);
[H,w] = freqz(b,1);
plot(w/pi,20*log(abs(H)))
title('butterfilter')
and you can design simple filter by
d=designfilt('lowpassfir','filterorder',n,'cutoffFrequency',fc,'samplerate',fs);
Filtered=filter(d,signal)%signal is the signal you wont to filter