Patent ID: 7542527
Filing Date: 2009-06-02
Classification: H03D

Abstract:
1. A semiconductor circuit for detecting and correcting a frequency offset in data communication for demodulating digital data from a high-frequency signal having a carrier frequency modulated based on the digital data, comprising: a digital IQ demodulator for performing quadrature demodulation on a digital signal obtained by digital conversion from an analog signal having been obtained by frequency-converting the high-frequency signal while using an oscillation output of a PLL as a reference frequency signal, an F-V converter circuit for converting a frequency of a digital output signal from the digital IQ demodulator to a voltage and outputting a demodulation baseband signal corresponding to the digital data after passing the digital output signal through a band-pass filter, a maximum value holding circuit for holding a maximum value of the demodulation baseband signal outputted from the F-V converter circuit, a minimum value holding circuit for holding a minimum value of the demodulation baseband signal, an averaging circuit for averaging the maximum value of the demodulation baseband signal and the minimum value of the baseband signal, a frequency offset detector for detecting a frequency offset amount on the demodulation baseband signal from the averaging circuit, and an offset correcting unit for correcting the frequency offset amount on the demodulation baseband signal by varying a threshold value for deciding data of the demodulation baseband signal outputted from the F-V converter circuit based on the frequency offset amount having been detected by the frequency offset detector.