| 摘要 |
PROBLEM TO BE SOLVED: To provide an orthogonal frequency division multiplex modulation circuit that employs first and second interpolators 7, 8 having IIR filters 71 , 73 , 81 , 83 to prevent a circuit scale of a logic circuit section from being increased and employs a frequency shifter 5 to ensure compatibility with an existing circuit. SOLUTION: The orthogonal frequency division multiplex modulation circuit is provided with; an inverse Fourier transform stage 3 that maps a digital modulation signal with N sets of subcarriers whose frequencies are centered to a half the sampling frequency to conduct inverse Fourier transform and outputs N sets of inverse Fourier transform signals; a frequency shifter 5 that shifts the frequency of N sets of the inverse Fourier transform signals toward high frequencies by a half the sampling frequency; a first interpolator 7 that interpolates an output signal from the frequency shifter 5 by a degree of 2; and a second interpolator 8 that interpolates an output signal from the first interpolator 7 by a degree of 2. The first interpolator 7 (2nd interpolator 8) is provided with digital delay circuits 72 , 74 , (82 , 84 ) such as IIR filter 71 being an IIR filter and delaying the input signal by a delay.
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