Graph of volts against frequency for HANN function

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derick007

Joined Feb 5, 2013
11
The graph of such a function is the well known sinc x function with an amplitude of 1/2v at f=0.

This "total" sync function is the summation of 3 seperate sinc x functions. The first of these is similar to the "total" function in that it has an ampiltude of 1/2v at f=0.

Assuming the HANN function contains a sinusoid of frequency f1, then the other 2 sinc x functions will be centred at f-f1 and f+f1 with amplitudes of 1/4v.

I have found these 2 sinc functions to have a minus sign in front of them meaning their amplitudes are -1/4v at their centre frequncies. But any graphs I have found on the net, indicate they have amplitudes of +1/4v at their centre frequncies. It is though the minus sign has been ignored/forgotten.

I have been struggling with the maths to see how it is possible to ignore the minus sign or how the maths can be used to change it from - to +?
 
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