Hello, I'm trying to implement an AGC software in our RF application. The setup is the following:
- B200mini - master clock rate: 16 MSPS - fs = 32 KSPS - Receive samples in blocks of 32k (1 second). I made a tiny program, where I change rx_gain every 1 seconds (just after rx_streamer->recv() returns) adding or substracting 30 dB. To find out when a change in rx_gain actually affects the received samples I implemented a simple detection algorithm. Ignoring the non-deterministic latency, at least *I would expect the time between changes to be 1 seconds as well* (µ = 1 seconds, with some non-zero variance), the same periodicity they were invoked with. However, this change takes on average 1.016 seconds (see figure <https://drive.google.com/open?id=1j1kiJt334FjOwczgbYsp0IITNlIkpeZR>). *This means for each set_rx_gain call the radio is taking longer and longer to apply the change *(see figure <https://drive.google.com/open?id=10u3X7Yoa5mlCbUbtmddMxVuTF61QQDYR>). Example: t = 1 s -> Recv previous block and change gain t = 2 s -> Recv previous block and change gain t = *1.016* -> Change in gain detected in previous block *(OK, latency to change gain is around ~0.016 ms)* t = 3 s -> Recv previous block and change gain t = *2.032* s -> Change in gain detected in previous block *(I would expect ~2.016)* t = 4 s -> Recv previous block and change gain t = *3.048* s -> Change in gain detected in previous block *(I would expect ~3.016)* (...) t = 60 s -> Recv previous block and change gain t = *59.96* s -> Change in gain detected in previous block *(After 60th call to rx_gain, latency has increased to almost 1 second!)* Is there any rational reason why this is happening? (I've tried longer periods, up to 10 seconds, with the same result). Regards, Brais.
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