Phase-locked synchronous oscillators as carrier recovery networks

Phase-locked synchronous oscillators (PLSOs) can synchronize, track, filter, divide, and improve the signal-to-noise ratio (S/N) by as much as 30 dB. They have high skirt selectivity (greater than 60 dB/octave) and can perform the above functions with an S/N level as low as -10 dB. PLSOs have been used as clock and carrier recovery networks in various bit rate QPSK burst-mode modems, and excellent results have been obtained. The recovered carrier and clock operation resulted in a BER degradation of only 0.2 dB compared to hard-wired cases. No clock and carrier cycle skipping has been observed for 72 hours at Eb/No = 7 dB, while acquisition time has remained under 500 ns. The PLSO has also been used in data remodulation loop in continuous-mode operation.