| 摘要 |
PURPOSE:To avoid a passing phase from being fluctuated even when the frequency of an interference wave is fluctuated by providing a delay means or the like inputting an extracting interference signal and giving a delay equivalent to a delay of a band pass filter to this input. CONSTITUTION:The band pass filter 11 suppresses components other than the interference wave of an input signal 101 to improve the C/N of the interference wave at the output. A phase comparator 12 compares the phase of band pass filters 11, 15 to output an error signal. A low pass filter 13 limits the band of the error signal. A voltage controlled oscillator 14 outputs the oscillated output of a frequency controlled by the output of the low pass filter 13 as an extracted interference signal 102. Since the extracted interference signal 102 is phase-locked to the interference wave included in the output of the band pass filter 11 by a phase locked loop comprised of the phase comparator 12, the low pass filter 13, the voltage controlled oscillator 14 and the band pass filter 15, the signal 102 is coincident with the interference wave included in the input signal 101.
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