Patent ID: 9297842
Filing Date: 2016-03-29
CPC Classification: G01R,H02M,H03L

Claim Text:
1. A frequency detection apparatus of a periodic signal comprising: a delayed signals output circuit, and a judgment circuit, wherein the periodic signal is a string of pulses and the time interval of pulses changes according to time, the delayed signals output circuit inputs the periodic signal and outputs a second periodic signal which is delayed to the periodic signal by a predetermined delay time, the judgment circuit inputs the periodic signal and the second periodic signal, and outputs a judgement signal, in the case when the time interval of pukes decreases according to time, the judgement circuit outputs the judgement signal when two consecutive pulses of the periodic signal are located between two consecutive pulses of the second periodic signal, and in the case when the time interval of pulses increases according to time, the judgement circuit outputs the judgement signal when two consecutive pulses of the second periodic signal are located between two consecutive pulses of the periodic signal.