## scaling for periodic signal using hann window

on 13 Mar 2012

### Wayne King (view profile)

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

Lisa Justin

### Lisa Justin (view profile)

on 13 Mar 2012

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?

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### Wayne King (view profile)

on 13 Mar 2012

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));
```

Lisa Justin

### Lisa Justin (view profile)

on 13 Mar 2012

sc is same as flattop you mean. no not true

Lisa Justin

### Lisa Justin (view profile)

on 13 Mar 2012

the signal is periodic remember

Wayne King

### Wayne King (view profile)

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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