Re: [Discuss-gnuradio] AGC using RXPGA on MxFE

[Sachi]

Hi, Eric

Would you please iterate more on the concept of PGA? 
I don't understand it quite well.  Is it just an
amplifier after the ADC, so that the 16-bit signed
integer is multiplied by the value of pga? Or, let's
say the pga is 10, is it true that the p-p value of
the adc is not 1V--1V, but 0.1V - -0.1V, so that the
ADC can quantize the signal more subtly?? 

And how about the Tx path? 

Thanks

Sachi

--- Eric Blossom <address@hidden> wrote:

> On Tue, Jul 19, 2005 at 06:08:27AM +0500, Ahmad
> Sheikh wrote:
> 
> > The USRP user guide states that there is 20 db of
> gain on the
> > USRP. Assuming that this is on the Receive path
> Programmable Gain
> > Amplifier on the MxFE, can this be used as an AGC?
> 
> Yes.
> 
> > I want to control the strength of the signal
> received. The way to do
> > this, I think, would be to dynamically alter the
> value written to
> > the Rx A/Rx B registers, using some feedback
> control
> > mechanism. Would this control be on the FPGA, or
> GNU Radio
> > Python/C++ software using
> usrp.source_c().set_pga()? Is there
> > already some structure provided to do this?
> 
> The easiest way is using usrp.source_c().set_pga()
> 
> Eric
> 
> 
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