Re: [Discuss-gnuradio] Inquiry about automatic gain control

[Matt Ettus]

address@hidden wrote:
> Brian,
>
> If you refer to the usrp\fpga\sdr_lib\adc_interface.v
>
> this is a comment stating: \\level sensing for AGC
> on line 67 of the verilog code file.
>
> I have read on the wiki that AGC can be implemented by moving resistors around,
> can you elaborate on this: which resistors, and on what board?
>
> I am assuming that there is some sort of feedback loop for the FPGA to an
> amplifier which uses the RSSI, is there not one? 
>   


By moving some resistors around you can implement a completely analog 
AGC function on the RFX900, 1200, 1800, and 2400.  It will not work on 
the RFX400.

In general, there are many ways you can implement AGC, depending on 
where you implement the RSSI sensing and the control functions.  Nothing 
has been done to prevent you from doing any of these, but it is an 
exercise left to the user, as they say.

Matt