| 摘要 |
PROBLEM TO BE SOLVED: To obtain satisfactory reception characteristics, even when an adjacent channel exists near a desired channel in an OFDM transmission system. SOLUTION: Power of only the desired channel is obtained, and a gain control means 18 is controlled so as not to amplify the power when it is large and so as to amplify the power, when the power of the desired channel is small by a power of desired channel detecting means 19. The desired channel detecting means 19 has a method for measuring band pass filter output of a narrow band. Other than this method, the ratio between input signal power and output signal power to/from a digital filter for removing loop back components after digital quadrature modulation can be obtained, when the ratio of output power to input power is larger than predetermined ratio between an input signal and an output signal when no channel interference exists, power for interfering the adjacent channel is regarded as large, the power of only the desired channel is regarded as being small, and the gain control means 18 is controlled so as to amplify the power of the input signal of a discrete Fourier transform circuit as well.
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