Re: [Discuss-gnuradio] FPGA Gain?

[Trond Danielsen]

2007/7/10, Eric Cottrell <address@hidden>:
> Hello,
>
> The LFRX daughterboard on the USRP has 20 dB of gain.  I seem to remember that 
> 10 dB of that gain is from the FPGA.  I assume that this gain is after the ADC? 
>  If so, is it really useful?
>
> I relate digital gain to zoom on a digital camera.  The analog gain is the 
> optical zoom and the digital gain is the digital zoom.  Digital cameras have 
> 10x or more digital zoom but it is not really useful.  At high digital zooms 
> you get lower resolution and the picture is blocky.  Optical zoom is more 
> useful as it comes before the digitizer.
>
> So if I have noise values of 35 and signal values of 40 then I get values of 
> 350 and 400 after the 10 dB digital amplifier.  I may see a higher amplitude 
> signal but how do I gain anything?  Am I missing something?
>
> 73 Eric

Hi Eric,

The ADC has a programmable gain stage prior to sampling. Could it be
that one you are thinking of?

Regards,
--
Trond Danielsen