Carrier recovery circuit for use in a multi-level phase shift keying demodulator

In a demodulator for use with a multi-level phase shift keying (p.s.k.) signal having N phase levels, the p.s.k. signal which includes a carrier signal is frequency multiplied by a factor N in a multiplier filtered and frequency divided by the factor N to enable the carrier signal to be reconstituted at a terminal. To enable the demodulator to work at different data rates, and to enable filters to have sufficiently precise characteristics, the received p.s.k. signal is initially converted to base-band in mixers to which is applied a locally generated signal nominally at the carrier frequency.