Patent ID: 6396884
Filing Date: 2002-05-28
Classification: H04L

Abstract:
An automatic frequency control circuit in a receiver for receiving and quadrature-demodulating a multilevel quadrature-modulated signal transmitted during a preamble period and a data period subsequent to the preamble period, comprising:phase difference detection means for obtaining a phase difference between pattern signals per period on the basis of a quadrature-demodulated pattern signal component and a pattern signal component one period before the quadrature-demodulated pattern signal component, the pattern signals being repetitively transmitted with the same pattern from a transmitter during the preamble period; average value calculation means for calculating an average value of first phase differences between the pattern signals repetitively output from said phase difference detection means, thereby obtaining a second phase difference in units of symbols in a current burst; weighting means for weighting the second phase difference from said average value detection means and a third phase difference up to a previous burst, thereby obtaining a fourth phase difference up to the current burst; and phase correction means for correcting a demodulated received signal on the basis of the fourth phase difference from said weighting means.