Experimental Performance of a Frequency Measurement Circuit

摘要

The accuracy with which the frequency of a sinusoid and a pulsed sinusoid can be measured using a phase locked loop is investigated. A frequency divider is inserted into the feedback loop and a very stable local clock is used to determine the effect of these modifications on the frequency measurement accuracy of the phase locked loop. The primary result is that there is no theoretical limit to the accuracy of frequency measurement, independent of gate time, using a phase locked loop with frequency division and very stable clocks. The practical tradeoffs for improved frequency measurement accuracy are a higher required signal to noise ratio and a reduction of the frequency capture range of the phase locked loop.