1991 年 15 巻 46 号 p. 19-24
A QPSK demodulator system using a digital PLL for carrier recovery is studied based on computer simulation. We propose a double-loop-system (PLL and AFC) and a digitally controlled AFC which can expand the frequency pull-in range of the PLL. The results show that the system can track ±2.4MHz and it can be locked within 0.5sec when it operates in C/N=2dB.