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What is the difference in the shown waveforms conceptually? 
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#1
Jul1513, 01:08 AM

P: 191

Hi guys ,
My present doubt is regarding the waveforms shown in the image. The first plot is a impulse train. what is the difference having δ(t) in one plot and 1 at t=0, (0 else where) in a second case. whether time or frequency is the case... 


#2
Jul1513, 02:18 AM

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In the second one, at t=0, f(t)=1. In the first one, f(t=0) is undefined. It will probably help you understand if you consider the situations you'd have to find the area under the train in each case ... or do a fourier transform. 


#3
Jul1513, 03:48 AM

P: 191

Sir , thanks for the eye opener............ But how does this concept do apply practically.........for example when viewing spectrum analyzer of a periodic signal, the frequency domain we see is what mathematically?Is it impulse functions or spikes...? How do we treat this impulses practically?



#4
Jul2713, 06:45 AM

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P: 1,957

What is the difference in the shown waveforms conceptually?
A spectrum analyser cannot represent infinite pulses of zero width so we see each as a limited amplitude pulse with an area determined by energy. A train of Dirac delta pulses is a Dirac comb.
The spectrum of a Dirac comb is itself a Dirac comb. Take a look at... https://en.wikipedia.org/wiki/Dirac_comb 


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