DEMODULATION CIRCUIT FOR OFDM

摘要

PROBLEM TO BE SOLVED: To provide an orthogonal frequency division multiplexing OFDM synchronization circuit with an excellent demodulation characteristic even in the case that the synchronization circuit is applied to a transmission line whose delay dispersion differs. SOLUTION: A signal not passing through a delay circuit 10 receives hast Fourier transform FFT for a preamble period and a modulation component elimination circuit 50 eliminates a modulation component. A filter circuit 60 filters the signal whose modulation component is eliminated and provides an output of a frequency area phase and amplitude signal 340. On the other hand, a transmission line estimate circuit 30 estimates an impulse response 310. The estimated impulse response 310 is given to an FFT circuit 40, where it receives FFT and becomes a transmission line estimate phase and amplitude signal 330. A phase and amplitude signal selection circuit 70 compares the signals 340 and 330 at the end of the preamble period and selects a signal which is close to a signal representing a state of an actual transmission line as a phase and amplitude signal 350. The signal passing through the delay circuit 10 receives FFT after the end of the preamble period and a detection circuit 80 detects the resulting signal by using the phase and amplitude signal 350.