Patent ID: 7098967

Claim:
A receiving apparatus for performing OFDM modulation on a received signal having a plurality of segments, the received signal having a received frequency band, comprising: a first local oscillator for generating a first local oscillating frequency signal; a first mixer which converts a frequency of the received signal into a first intermediate frequency signal using the first local oscillating frequency signal, said first intermediate frequency signal having a frequency higher than the frequency of the received frequency band; a second local oscillator for generating a second local oscillating frequency signal having an offset frequency that is offset from the first intermediate frequency signal; a quadrature mixer which performs quadrature detection of an output of said first mixer by using the second local oscillating frequency signal; a numerical control oscillator which generates a complex wave with the offset frequency; a control section which changes a sign of the offset frequency of said second local oscillator and changes a sign of the complex wave of said numerical control oscillator according to a frequency of a received and selected segment that is part of the received signal; a complex multiplier which complex multiplies the output signals of said quadrature mixer and the complex wave generated by said numerical control oscillator to correct the offset frequency, and outputs I and Q signals; low pass filters which cut off high band components of the I and Q signals outputted from said complex multiplier, respectively; and an OFDM demodulator which performs a demodulation process including complex Fourier transform, deinterleave, and error correction by using output signals of said low pass filters.