| 摘要 |
PROBLEM TO BE SOLVED: To detect frequency at high speed by a simple hardware structure suitable for integration into a semiconductor circuit. SOLUTION: A variable filter part 1 is provided, which includes a subordinate connection of multistage of unit filter parts 1A, 1B and 1C structured of signal selection parts for comparing a level of an output signal of a curtailing part 13 to curtail a half of output signals from a high-pass filter 11 with a level of an output signal of a curtailing part 14 to curtail a half of output signals from a low-pass filter 12 so as to select the output signal with a higher level and output it to a next stage. A frequency of an input signal is detected from selection results of the output signals in the signal selection parts of the respective unit filter parts 1A, 1B and 1C. COPYRIGHT: (C)2011,JPO&INPIT
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