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Re: [Discuss-gnuradio] Question about sampling

From: cswiger
Subject: Re: [Discuss-gnuradio] Question about sampling
Date: Wed, 16 Mar 2005 17:48:06 -0500 (EST)

On Wed, 16 Mar 2005, Dinkar Bhat wrote:

> I joined this group recently and have learnt a lot.

Join the crowd (that are learning a lot)

> I had a rather
> fundamental question. Suppose I sample the
> IF output (say, centered at 40 Mhz) of a tuner/mixer tuned to a ATSC DTV
> channel (6Mhz wide), and I want to detect the
> pilot frequency which is added to the channel during transmission, would
> I have to sample the IF
> at much higher than 2*Nyquist fy? The reason I ask is that the pilot

If the IF is bandlimited (say 40 +- 4Mhz) you can sample at a much lower
rate using 'bandpass sampling', use a slower ADC and get fy translation
at the same time. For example, a tuner we use is centered at 36Mhz, our
ADC samples at 64Mhz ( < 2* IF ) but the IF appears to be at 28Mhz
( 32 - ( IF - 32 )).


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