[Discuss-gnuradio] AGC on the RFX900 board

[Sundaram Vanka]

Hi,

I have a few questions about the (analog) AGC on the AD8347 mixer chip on the Flex900 daughterboard. 

1. Given a signal received with some known power, is it possible to read the programmed AGC gains (and thereby find the mixer's noise figure)? 

2. Is it possible to lock these gain settings? If not, can the AGC functionality be disabled? 

3. How fast does the AGC track changes in signal power? 

4. If (1), (2) are not possible, is it still possible to know the RX noise figure?

I'd appreciate some inputs :) If I understand correctly, to calibrate the receive SNR, we need to know the RX noise floor (seen in software). For this we need to know the RX noise figure...

To provide some context, the following is our immediate application: we have a coded 16QAM system implemented on GNURadio. We want to measure the Frame Error Rate vs. Es/No ("per-symbol SNR") for this system. The TX and RX have separate USRP boards, each with a RFX900 daughterboard. A coaxial cable connects the TX and RX antenna ports. With this setup, we vary the transmit power and measure the frame error rate. To compare these results with a Matlab model, we need to know the received Es/No: for that we need the RX noise figure...and hence my question above.

I'd appreciate your help. 

Thanks in advance,

Regards

Sundar