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## Re: [Discuss-gnuradio] Hello everyone. I am a new here. I have some ques

 From: Tom Rondeau Subject: Re: [Discuss-gnuradio] Hello everyone. I am a new here. I have some questions. Date: Fri, 21 Mar 2008 17:21:28 +0000 User-agent: Thunderbird 2.0.0.12 (Windows/20080213)

```Alex Miua wrote:
```
So I have started reading Discrete Time Signal Processing by Oppenheim / Schafer / Buck. Chapter 4/ Page 168 says : -
Which edition are you using? I have the second edition and this is on page 142 :) I'm assuming your copy is a new edition.
x_s(t)=x_c(t)s(t)
```         =x_c(t) Sigma ( from n = -inf to inf ) [ delta (t-nT) ]
```
Through the sifting property of the impulse function , x_s(t) can be expressed as : x_s(t) = Sigma (from - inf to inf ) [ x_c(nT) delta ( t-nT) ] Now this version of the sifting property is for the DISCRETE impulse function NOT the continuous Dirac delta function, but just before the discussion starts it says that delta(t) is the unit impulse function or the Dirac delta function. Is this a typo ? Shouled this have been the discrete delta function? If it is'nt, how do the above steps hold? Thank you,
```Alex.
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```
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They are still representing all of this in the time domain. The sampling function is a continuous time signal as is x_c(t) as it x_s(t) where the discrete time representation is x_s[n] = x_s(nT).
```
I don't see this as a typo, and I don't see how this changes anything.

Tom

```