Honored Contributor
Honored ContributorI did a new matlab model (private) using rtl model of nco (at tx and rx) as well as bit true modelling (except for loop filter which Ikept normalised for now).
Input: variety of symbols (BPSK,QAM) Tx: RRC upsampling by 2 to Rs*2, then mixing with 0.01Fs and directly taking I&Q of mixer as RF (this is just to avoid having high sideband and hence no need for filter) Rx: nco and loop filter. Thus the loop works at Rs*2 rate. I update the nco word once every 5, or 10,50,100 samples reverting back to initial nco word. Hence update rate is Rs*2/5...etc. The loop filter set to 0.0001 for alpha but other values work. I then use RRC decimating by 2 down to Rs after loop (RRC not inside loop). It locks for clean or jittered single tone for all cases (BPSK,QPSK,16QAM) but works only for BPSK random symbols (may be it needs more research to work for all but I understand from literature it shouldn't work for QPSK and other QAMs efficiently unless aided by slicing results)
