| 摘要 |
PROBLEM TO BE SOLVED: To attain excellent demodulation by eliminating the effect of inter-symbol interference(ISI) in the case that a delay time of a delay wave generated in a multi- path propagation line exceeds a guard interval period. SOLUTION: In the orthogonal frequency division multiplex(OFDM) demodulator, a variable delay section 3100 delays a correction complex signals output of an adaptive filter section 30 by a valid symbol period +α, a complex multiplier 3101 and a sum average arithmetic section 3102 apply correlation arithmetic operation after and before the delay, integration arithmetic sections 3103, 3104, square arithmetic sections 3105, 3106 and an adder section 3107 apply their respective operations to real and imaginary parts of the result to obtain a correlation square signal. Furthermore, by means of a tan<-1> arithmetic section 3110 a phase rotation angleθis obtained from the result of the integration arithmetic operation. A peak detection/hold section 3108 holds theαandθat a peak value of the correlation square signal. According to the operations above, each estimate value of a delay time of a delay wave, an amplitude ratio of the delay wave to a desired wave, and a phase difference between the desired wave and the delay wave is found, and a filter coefficient generating section 3109 generates a filter coefficient from each estimate value and provides an output to an adaptive filter section 30.
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