| 摘要 |
PROBLEM TO BE SOLVED: To exactly separate and extract the FM signal of desired frequency band by subtracting an FM signal, which is delayed corresponding to a demodulation signal, from a frequency multiplex signal. SOLUTION: In order to trap the FM signal while utilizing correlation, a delay circuit 22 is divided into a fixed delay circuit 31 and a variable delay circuit 32 and in addition to fixed delayτdue to the fixed delay circuit 31, further, variable delay proportional to a demodulation level corresponding to a modulation level is performed by the variable delay circuit 32. Assuming that exp(-jwc t) is inputted to the delay circuit 22, its output becomes exp[-j wc (t-τ)+τ.Δw.COSpt}] and at the delay circuit 22, the phase modulation ofτ.Δw.COSpt is performed. Namely, in order to cancel the FM signal while utilizing correlativity found delay timeτseconds later, it is shown that it is necessary to perform not only delay just by the timeτthrough the fixed delay circuit 31 but also to perform the phase modulation ofτ.Δw.COSpt through the variable delay circuit 32.
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