CARRIER RECOVERY CIRCUIT

PURPOSE:To attain high-speed pulling-in by providing a waveform so as to cause an output corresponding to a phase difference on a part having a hysteresis in a carrier recovery circuit provided with a phase comparator having an output characteristic having hysteresis at a part of phase difference + or -pi. CONSTITUTION:The phase comparator is provided with the following output characteristic. That is, hysteresis is provided on a part of phase difference pi, and the hysteresis curve is not horizontal but still increasing/decreasing. That is, the output is increased in a positive direction in the increase in the phase difference attended with its increase and the output is increased in a negative direction in the phase difference decreasing direction attended with the decrease. The increasing/decreasing characteristic may be formed as the extension of 0-+ or -pi/2 and + or -2pi-+ or -3pi/2 as they are, or in a monotonous increase/ decrease function different from them. The curve is written in the ROM 40 and it is read by using inputs I=costheta, Q=sintheta as addresses. That is, the curve is selected by using an output of the circuit 32 and an output of the flip-flop 42 and each value in the curve is read by the input Q.