| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit which decides a transmission mode and a guard length correctly in a short time even in a fading environment. SOLUTION: Disclosed is the transmission mode and guard length detecting circuit of a radio device using an orthogonal frequency-division multiplexing system comprising: a one-symbol delay circuit which delays a received main wave as much as real data of a symbol; a guard correlating circuit which calculates the correlation between the main wave and the output of the one-symbol delay circuit; a moving average circuit which calculates the moving average of the output of the guard correlating circuit by previously set symbols; a maximum value detecting circuit which detects a peak value of the output of the moving average circuit for every symbol; a maximum value integrating circuit which integrates the output of the maximum value detecting circuit by the previously set symbols; a guard maximum position shift quantity integrating circuit which calculates the difference between a reference wave having a constant period and a peak value interval of the output of the maximum value detecting circuit as a shift quantity, integrates shift quantities by symbols, and outputs the integrated value; and a maximum value weighting circuit which varies the output of the maximum value integrating circuit based upon the shift quantity. COPYRIGHT: (C)2008,JPO&INPIT
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