Patent ID: 9160588
Filing Date: 2015-10-13
Classification: H04B,H04L,H04W

Abstract:
1. A radio receiver using a modulation scheme in which a frequency shift from a radio transmitter appears as a DC offset in a demodulated signal, comprising: a synchronization word pattern detection circuit obtaining the DC offset from a difference between a direct current value of a predetermined number of symbol patterns of the demodulated signal and a known direct current value of symbol patterns of a synchronization signal; a first DC offset correcting circuit adjusting the value of the DC offset output from the synchronization word pattern detection circuit; a symbol recovery circuit that performs high-speed pull-in processing by subtracting, from the demodulated signal, the value of the DC offset adjusted by the first DC offset correcting circuit to output a corrected demodulated signal; a second DC offset correcting circuit obtaining a residual DC offset from an average value of the corrected demodulated signal output from the symbol recovery circuit; and a local oscillator that performs low-speed pull-in processing by correcting an oscillation frequency based on the residual DC offset obtained by the second DC offset correcting circuit; wherein, after starting the high-speed pull-in processing, the first DC offset correcting circuit reduces the DC offset output from the synchronization word pattern detection circuit, over time in each predetermined period of time.