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Semiconductor circuit device

  • US 20060067435A1
  • Filed: 09/07/2005
  • Published: 03/30/2006
  • Est. Priority Date: 09/27/2004
  • Status: Active Grant
First Claim
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1. 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.

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