Patent ID: 8077784

Claim:
An OFDM (Orthogonal Frequency Division Multiplexing) demodulator in a receiving apparatus for receiving an OFDM signal, wherein the OFDM signal is a signal in which a scattered pilot signal is placed at a prescribed symbol interval in a time axis direction and at a prescribed carrier interval in a frequency axis direction, a continuous pilot signal and a control information signal are placed at a prescribed carrier position, and an information transmission signal is placed in a remaining portion, the OFDM demodulator comprising: an FFT (Fast Fourier Transform) circuit for performing a fast Fourier transform on the OFDM signal; a circuit for extracting a scattered pilot signal from the fast Fourier transformed signal; a circuit for adding a phase to the extracted scattered pilot signal based on a position of the scattered pilot signal from a transmitting party; a memory for temporarily storing the phase-added scattered pilot signal and the information transmission signal; a memory interface for conducting write memory at a prescribed timing, starting read operation when a prescribed number of scattered pilot signals have been written and outputting the scattered pilot signals, and starting read operation at another timing and outputting the written information transmission signal; a carrier interpolation circuit for matching the phase of the scattered pilot signals received from the memory interface and performing interpolation in a time axis direction and a frequency axis direction; a complex division circuit for performing at a prescribed timing a complex division of the information transmission signal received from the memory interface by a result obtained from the carrier interpolation circuit; a plurality of circuits for performing interpolation in the time axis direction, and the plurality of circuits being selectable according to a reception condition wherein one of the circuits for performing interpolation in the time axis direction uses a diagonal interpolation method; and a circuit for detecting an end in the diagonal interpolation method; and a circuit for changing only a processing at the end to a time axis linear interpolation method.