# Carrier and timing not properly locking?

I have designed a simple BPSK system which is operating in UHF band. My transmit data rate is chosen to be 500 kbps. My receiver has AGC, timing recovery and carrier recovery bocks.

I am using Gardner timing recovery with 2 samples/symbol. The loop bandwidth for 2nd order loop filter for timing and carrier recovery is chosen to be

My signal level varies from -30 to -10 dBm at the receiver. I am observing the lock in carrier and timing is not constant. Is it because of the loop parameters or signal level or the header bits chosen for the carrier and timing recovery?

• Hi! That's pretty cool. Have you made sure your channel is flat? Jun 8 '20 at 14:34

• meaning it hasn't yet settled and you need to observe it for much longer. You should see a step there from which you can establish a 10% to 90% settling time, and from that you can estimate your loop BW using $BW \approx 0.35/t_r$ with BW in Hz and $t_r$ in seconds. (and be sure it actually converges to what looks like a step given you test with a fixed frequency offset) Jun 10 '20 at 2:19