Patent ID: 7664189

Claim:
An orthogonal frequency division multiplexing (OFDM) demodulator that demodulates an OFDM signal constituted by OFDM symbols and transmitted on a symbol-by-symbol basis, the OFDM symbol including at least an effective symbol corresponding to a signal to be transmitted, a known signal being scattered onto a predetermined subcarrier in each of the transmission symbol, the OFDM demodulator comprising: a Fourier transform performing unit for performing a Fourier transform operation on the OFDM signal; a known signal extracting unit for extracting the known signal, for each transmission symbol, from the signal having undergone the Fourier transform operation; a time dimension interpolation unit for performing interpolation on the extracted known signal in a time dimension using a time dimension interpolation filter, and estimating transmission path characteristics regarding all of the transmission symbols; a delay spread generating unit for generating a delay profile on the basis of at least one of the transmission path characteristics estimated by the time dimension interpolation unit and the OFDM signal not having undergone the Fourier transform operation, and determining a delay spread on the basis of the delay profile; a frequency dimension interpolation unit for performing interpolation on the known signal having undergone the time dimension interpolation in a frequency dimension using a frequency dimension interpolation filter having a pass bandwidth corresponding to the delay spread, and estimating transmission path characteristics of all of the subcarriers in the transmission symbols; and a waveform equalizing unit for equalizing a waveform of the signal having undergone the Fourier transform operation on the basis of the transmission path characteristics estimated by the frequency dimension interpolation unit, wherein the delay spread generating unit employs a time difference between a time point for a starting position of the Fourier transform operation performed by the Fourier transform performing unit and a time point at which a latest arriving path arrived as the delay spread.