| 摘要 |
PROBLEM TO BE SOLVED: To provide a demodulation circuit for orthogonal frequency division multiplex signals, that employs a digital filter 7 and a digital signal delay circuit 8, has a simple circuit configuration and a small occupied volume and can reduce the power consumption. SOLUTION: The demodulation circuit for orthogonal frequency division multiplex signals includes; an analog/digital conversion section 1 for converting a received signal whose center frequency is not zero into a digital signal; a digital orthogonal signal detection section 2 consisting of a digital signal delay circuit 8 for delaying the digital signal to obtain an I signal and of a digital full pass filter 7 for shifting the phase of the digital signal by 90-degrees to obtain a Q signal; a frequency shifter 3 for shifting the frequency of the I and Q signals to the frequency of a base band signal whose center frequency is zero; and an orthogonal frequency division multiplex signal detection section 6 having a fast Fourier transform section 14 for applying fast Fourier transform to the base band signal and having a digital demodulation section 15. The filter 7 is an infinite impulse response digital filter having a prescribed group delay characteristic and the delay circuit 8 has a signal delay equal to a group delay of the filter 7.
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