Semiconductor circuit device

A semiconductor circuit device 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 using the frequency offset amount as a feedback signal to a threshold value for deciding data of the demodulation baseband signal, the frequency offset amount having been detected by the frequency offset detector.