Patent ID: 7724694

Claim:
A Doppler frequency calculating apparatus that calculates a Doppler frequency, which is a magnitude of a time-dependent fluctuation of a characteristic of a transmission path through which an orthogonal frequency-division multiplexing (OFDM) signal is transmitted, the apparatus comprising: received signal point memory means for storing a received signal point of a sub-carrier having a reference carrier signal of the OFDM signal; modulated component eliminating means for eliminating a modulated component from the received signal point stored in the received signal point memory means; fast Fourier transform calculating means for receiving the signal point from the modulated component eliminating means from which the modulated component has been eliminated and for performing a fast Fourier transform thereon for each sub-carrier; and Doppler frequency calculating means for receiving an output from the fast Fourier transform calculating means and for calculating therefrom a maximum Doppler frequency above a predefined amplitude threshold.