# AGC detectors

Question asked by s.kannan on Dec 18, 2017
Latest reply on Dec 20, 2017 by srimoyi

In Slow attack AGC, does the detectors knows the gain of the upcoming stages in before-hand?

For example, take a look at the Rx chain front end

I set decremented gain steps for ADC and LMT to 0 and enabled inner high threshold of 10dBFS(disabling all the other thresholds) with decremented step of 2. I also set the gain of RF FIR to -12dB(which subtracted with +6dB to give net gain of -6dB). Now, If I keep on increasing the power level of my input signal(input to Rx), I'm seeing my hardware gain changes correspondingly. My question is, where should the power detector measures the power? Is it in between Half Band Filter and FIR?

If it is measuring the power at the above mentioned position then it doesn't consider the gain of Rx FIR , right?

But for my experiment, I'm seeing the response which also includes the FIR gain. For example, if I increase the input signal level from -51.1dBm to -50.1dBm my hardware gain reduces from 47dB to 45dB.

Here, if input is -51.1dBm, then the power at detector(including RX FIR gain) is -51.1+47-6=-10.1

When I increase my input level to 1dBm, then -50.1+47-6=-9.1(higher than my 10dBFS inner high threshold) so the hardware gain reduces by 2 steps. Here while calculating the power, it is considering the RX FIR gain. But how is this possible?