Analysis of interference effects on period-to-digital conversions

This paper analyses the effects of interference on period measurements based on crossings of a reference level. Due to interference superimposed on the input signal to be measured and/or on the threshold voltage of the timer, the starting and stopping points of the timing process can erroneously be triggered. The variability of the measurement increases proportionally to the interference amplitude and depends on the ratio between the interference frequency and the input signal frequency. Therefore, the effects of a given interfering signal depend on the input signal frequency and hence on the information embedded in it. Experimental data obtained from both a universal counter and a microcontroller validate the developed model.