Patent ID: 6081563
Filing Date: 2000-06-27
Classification: H04L

Abstract:
An AFC circuit of a digital demodulation device comprising:multiplication means for multiplying an input modulated wave signal by a local oscillation signal to output a detection signal;phase detection means for detecting a phase of the detection signal output from said multiplication means;frequency error detection means for detecting a frequency error of a phase detection signal output from said phase detection means, with a first frequency error detection characteristic in which a first frequency domain is defined as a detection range;first characteristic conversion means for converting a frequency error signal output from said frequency error detection means into a frequency error signal having a second frequency error detection characteristic in which a second frequency domain other than the first frequency domain is defined as a detection range;first average calculation means for calculating an average of frequency error signals output from said first characteristic conversion means, for each period of time;second characteristic conversion means for converting a frequency error signal output from said first average calculation means into a frequency error signal having the first frequency error detection characteristic; andoscillation means for controlling a frequency of the local oscillation signal supplied to said multiplication means, in response to the frequency error signal output from said second characteristic conversion means.