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Re: [Discuss-gnuradio] Low-cost hardware options

From: Peter F Bradshaw
Subject: Re: [Discuss-gnuradio] Low-cost hardware options
Date: Sun, 16 Jan 2011 13:38:38 +0800 (WST)

On Sat, 15 Jan 2011, Brian Padalino wrote:

> It's all about power, right?  So you may sacrifice sample rate for
> accuracy, but you can gain those bits back in the digital domain via
> filtering.  Only if you really want to see more than the 72dB of
> dynamic range the ADC supplies do you somewhat get screwed, I think.
> I've heard of people recovering very narrowband signals with
> narrowband blockers where the desired signal is below the dynamic
> range at their fastest sample rate, but through digital filtering were
> able to bring the signal out of that noise floor.  I haven't done it
> myself.

Of course. This is the principle that underlies Sigma-Delta ADCs.

In my view wider bandwidth and lower resolution is the way to go because
it gives the user a usefull trade off. That is, the user can opt for a
full bandwidth of F_s / 2 at the ADC's resolution or a narrower
bandwidth with processing gain. The processing gain is F_s / (2 * B)
where B is the bandwidth of the discrete filter.

Having said that it is usefull to maximize 2 * F_s / b with respect to
purchase cost where b is the number of ADC bits.


Peter F Bradshaw: http://www.exadios.com (public keys avaliable there).
Personal site: http://personal.exadios.com
"I love truth, and the way the government still uses it occasionally to
 keep us guessing." - Sam Kekovich.

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