RE: [Discuss-gnuradio] Reducing the ADC sample rate

[Robitaille, Michael]

Alfred reply is exactly why I would like to change the sample rate.  I am
operating at low frequency and would like to be able to look at the signal
with a different resolution in the frequency domain (time span = 1/sampling
rate, require ring more points in FFT to get resolution).  In my career I
have done lots of FIR filter design using Surface Acoustic Wave technology
and changing the sample rate and number of points was a very important tool.
As you know, with FFT you get images folding back into the spectrum
(aliasing).  Changing the sample rate moves those images to different
locations.  

I will check out using further decimation filtering.  Any information on the
use of decimation filtering would be appreciated.
 
Thanks,
Mike

-----Original Message-----
From: Robert McGwier [mailto:address@hidden 
Sent: Monday, November 14, 2005 6:34 PM
To: Alfred A. Aburto Jr.
Cc: address@hidden
Subject: Re: [Discuss-gnuradio] Reducing the ADC sample rate

The reason Matt, Eric, and I are questioning this is that the resampling 
done in software, is quite nice and completely adequate for this task.

Bob


Alfred A. Aburto Jr. wrote:

> > Matt Ettus wrote:
>
>>> Is there any other way to decrease the sample rate beside the 
>>> decim_rate?
>>>   
>>
>>
>> Why would you want to do that?
>>
>> Matt
>>
>>  
>>
> It may not be easy to do hardware wise, but just shifting the sample 
> rate to fit ones bandwiidth (FFT size and resolution, ...) of interest 
> seems ideal to me. This is often a problem in biological acoustics for 
> example because one needs a wide variety of bandwidths for different 
> species from blue whale to bat, but A/D cards are made at specific 
> sample rates often not quite meeting the requirements of bandwidth and 
> resolution ... no doubt similar problems exist in the electromagnetic 
> spectrum.
> Al
>
>
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>


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