FUNDAMENTAL FREQUENCY DETECTION USING PEAK DETECTORS WITH FREQUENCY-CONTROLLED DECAY TIME

摘要

Methods and digital circuits providing frequency correction to frequency synthesizers are disclosed. Dual switched-capacitor peak detectors connected to an input signal periodically sample the voltage of the input signal, and then determine a fundamental frequency of the input signal from the output of the dual switched-capacitor peak detectors. Both the sample period and the decay time of the dual switched-capacitor peak detectors are proportional to a time period between a previous pair of voltage peaks detected in the input signal. This makes the peak detectors immune to lower-amplitude oscillations which are often present within a single fundamental cycle in musical signals with strong harmonic components which might otherwise cause errors in frequency estimation. This is done without causing unwanted sluggishness in the transient response of the frequency detection process. The time period between the previous pair of detected voltage peaks is used to create a decay signal that initiates a capacitor decay time for each peak detector.