Carrier recovery in a PSK receiver

摘要

A complex multiplier 5 complex-multiplies base band signals x and y obtained from a receive signal by local oscillation signals c and s, to output complex detection signals p and q. A phase difference detecting portion 7 outputs the amount of the detected phase difference corresponding to the phase difference between the phase of the receive signal and the phase of the local oscillation signals. A loop filter 8 emphasizes its DC component. A local oscillation portion 6 outputs local oscillation signals having a frequency corresponding to the amount of the detected phase difference. A region judging portion 9 judges which of regions on a complex plane is one to which the base band signals belong, and outputs a region signal. A most frequent region judging portion 10 judges which of the regions is one in which the base band signals are concentrated most frequently upon input of the region signal a predetermined number of times. An initial phase generator 11 generates an initial phase corresponding to a most frequent region. The local oscillation portion 6 sets the initial phase as an initial value of the phase of the local oscillation signals. It is first judged which of the regions previously obtained by division on the complex plane is one in which the complex base band signals are concentrated most frequently, and the initial value of the phase of the local oscillation signals is set on the basis of the results of the judgment, so that a carrier can be reproduced in simple construction while preventing a hang-up phenomenon.