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Re: [Discuss-gnuradio] No need to high speed A/Ds !!

From: Linus Gasser
Subject: Re: [Discuss-gnuradio] No need to high speed A/Ds !!
Date: Thu, 26 Jun 2003 15:10:34 +0200
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On Mercredi, 25 Juin 2003 15.14, Saeed Beyty wrote:
> Hi again
> Some while ago there was an idea about using a F/V convetror before the A/D
> section,at the front-end section;as you know one of the main problems
> building the ideal SDR is the slow A/Ds ( although there are some really
> high speed ones, but still way to go till the ideal SDR ! ) So it is a
> great job making a trick to overcome this dilemma. i once wrote about it to
> the discuss but it was not accepted so much
> :http://mail.gnu.org/archive/html/discuss-gnuradio/2003-05/msg00005.html
> if we think of a F/V cheap as a FFT generator one, then not only the
> required bandwidth and therefore the required sampling rate is reduced but
> also we could do some demodulations much more easier, with respect to the
> fact that today most of modulations are frequency domain based. in the case
> of non-frequency based demodulations  such as AM or ASK, just an IFFT
> (inverse FFT ) will solve the problem,regenarating the original signal,then
> this could be a ideal and universal radio paltform. please take a little
> while, thinking about this idea, and write me your feedback.

And how do you sample your voltage? For some simple modulation schemes you can 
perhaps do some of the processing in the F/V converter, but for a general 
SDR, this is not a good thing.`
 Let's put it this way: there is no way this solution can send/receive 
anything like 64QAM or so. If you just want to have some FSK, this may work. 
But 802.11 and all others are going QAM...


Linus Gasser                        Phone:       +41 21 693 5635
EPFL                                FAX  :       +41 21 693 4312
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