要在两个全周期通过之前检测出慢变信号的频率是非常困难的。因此,设计用来测量慢变信号“瞬时”频率的仪器,如心跳(大约60个脉动/分或1Hz)或慢速马达(33转/分,约0.5Hz)监测仪,的确是个复杂的问题。传统的设计方法失败的原因是测量频率需要有若干个有效的统计过程,并且采集这些不连续值,需要 It is very difficult to detect the frequency of slowly varying signals before two full cycles pass. Therefore, designing instrumentation to measure the “instantaneous” frequency of slowly varying signals, such as a heartbeat (about 60 pulses / minute or 1 Hz) or a slow motor (33 rpm, about 0.5 Hz) is a complex problem . The reason for the failure of the traditional design method is that it requires several valid statistical processes to measure the frequency, and the collection of these discontinuities requires