| 摘要 |
PURPOSE:To eliminate the entry of the 2nd higher harmonic component to a base band and to detect a wave even if the frequency band of an FM signal subjected to Hilbert conversion overlaps with that of an FM signal as it is by detecting said two types of FM signals, rendering the 2nd higher harmonic component to obtain signals of the same phase and reverse one with respect to a base band component and calculating them so as to cancel the 2nd higher harmonic component. CONSTITUTION:A pair of quadrature detection circuits 10 and 11 composed of a multiplier 1 and a delay circuit 2 are installed. The delay time of a delay circuit 13 for delaying an input signal by n-samples corresponds to that of a converter 12. Outputs of the pair of quadrature circuits 10 and 11 are added by an adder 14. This addition cancels the item of the 2nd higher harmonic component, and only the item of the base band component is outputted. More over its output goes to a two-folded level, and a detection gain can be taken generously.
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