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## Re: [Discuss-gnuradio] Impulse response in DVB-T, someboby knows how to

 From: Tom Rondeau Subject: Re: [Discuss-gnuradio] Impulse response in DVB-T, someboby knows how to calculate? Date: Sun, 2 Oct 2016 19:03:43 -0400

On Sun, Oct 2, 2016 at 2:40 PM, Cinaed Simson wrote:
On 10/01/2016 04:46 PM, Juan Antonio wrote:
> Hello, someone would know how to calculate the impulse response of a
> COFDM, DVB-T channel with an SDR device?
>
>
>
> _______________________________________________
>

An inverse DFT on a sinc function in the frequency domain yields a sine
function in the time domain. And a DFT on the sine function in the time
domain yields a sinc function in the frequency domain.

No, the DFT of a sine function is an impulse. More formally, a Dirac delta function.

The sinc function is the result of a truncated sine wave where the sine wave is multiplied by a square wave. The DFT of a square wave is a sinc, so with a truncated sine wave in the time domain, you are convolving a sinc with a delta function in the frequency domain.

Tom

I presume the "C" in COFDM means to chop up the bandwidth into carriers
such that the sinc function in one channel hits nulls in the other
channels.

Piece of cake in theory.

There's a gr-dvbt project on github

https://github.com/BogdanDIA/gr-dvbt

I don't know anything about it - I don't even know if it works.

-- Cinaed