| US 7,542,527 B2 | ||
| Frequency offset correction circuit device | ||
| Jun Ogawa, Souraku-gun (Japan); and Mototugu Shiraiwa, Yokohama (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Sep. 07, 2005, as Appl. No. 11/219,774. | ||
| Claims priority of application No. 2004-278594 (JP), filed on Sep. 27, 2004. | ||
| Prior Publication US 2006/0067435 A1, Mar. 30, 2006 | ||
| Int. Cl. H04L 27/06 (2006.01); H04L 27/00 (2006.01); H03K 9/00 (2006.01) | ||
| U.S. Cl. 375—340 [375/316; 375/317] | 11 Claims |
| 2. 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,
a frequency converter circuit for frequency-converting the frequency offset amount having been detected by the frequency offset
detector,
a filter bandwidth correcting unit for correcting a bandwidth of the band-pass filter based on a frequency converted value
corresponding to the frequency offset amount having been calculated by the frequency converter 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.
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