Asked by Lisa Justin
on 13 Mar 2012

How can i scale for periodic signal using hann window. i know for flattop i.e 1/sum(window)but i do not know how to scale with hann window with a periodic signal. kindly help

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Answer by Wayne King
on 13 Mar 2012

Accepted answer

Hi Lisa, it should be the same:

t = 0:0.001:1-0.001; xn = cos(2*pi*100*t); w = hanning(length(xn)); x = xn'.*w; sc = 1/sum(w); xdft = fft(xn); xdft = xdft(1:length(xn)/2+1); y = sc*xdft; plot(abs(y));

Wayne King
on 13 Mar 2012

It's not the same as the flat top window, because the sum of the two windows is not the same.

w = hanning(length(xn));

w1 = flattopwin(length(xn));

sum(w)

sum(w1)

Accordingly the reciprocal of the sums is not the same.

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## 1 Comment

## Lisa Justin (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/32101#comment_67917

xn=signal;%%%periodic signal

w=flattopwin(length(xn));

x=xn.*w;

sc=1/sum(w);%%%%scaling

y=(fft(x)).*sc

please how would i scale if i want to usse hann window instead. what would 'sc' be?