| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency recovery circuit that detects a frequency error of a recovered carrier signal with high accuracy to make the accurate recovery of the frequency possible even when disturbance such as CWM disturbance is added to an inputted digital modulation wave. SOLUTION: Differential devices 32, 42 obtain the differences of coordinate values between two consecutive times as symbol phase differences with respect to Q and I axes on an I-Q plane for a symbol of a digital modulation wave after a frequency is converted by a complex multiplier 17, changeover devices 34, 44 extract them when they are within a prescribed detection range set by threshold value discrimination devices 33, 43 and they are fed to a low pass filter 52 via code discrimination devices 35, 45 where they are integrated to detect a frequency error which is given to a numerical controlled oscillator 53 as a control signal and recovered carrier signals 18, 19 are generated through a sine/cosine converter 54. |
