Measurement of Absolute Phase Error of Digitizers

Abstract

This paper proposes a method for the measure-1 ment of digitizer absolute phase errors, defined as the phase 2 displacement between the digitized output and the input analog 3 waveform. The measurement procedure is based on the use of a 4 phase reference signal (PRS), which is theoretically synchronous 5 with the input analog waveform and that triggers the digitizer 6 sampling clock. From the characterization of the waveform 7 generator phase response and the measurement of the time 8 delay of the digitizer sampling clock with respect to the PRS, 9 an accurate evaluation of the digitizer absolute phase error is 10 obtained. The method has been applied to a high-performance 11 digitizer, measuring the absolute phase errors of two different 12 channels. The expanded uncertainty of the method has been 13 quantified as a few microradians at 50 Hz and 150 µrad 14 at 20 kHz.

Uncertainty evaluation on the absolute phase error of digitizers

“…To the best of the authors' knowledge, direct measurement methods able to quantify this phase error are not available. Therefore, the authors propose an indirect measurement method, which has been fully described in Crotti et al (2019); here, it is only briefly summarized. It is based on the introduction of a Phase Reference Signal (PRS), that is a square wave, having the same frequency of the input signal.…”

“…In Crotti et al (2019), the same authors presented a measurement procedure for the evaluation of the absolute phase errors of a digitizer, with an experimental validation. Here, the attention will be focused on aspects not fully addressed by Crotti et al (2019).…”

“…In Crotti et al (2019), the same authors presented a measurement procedure for the evaluation of the absolute phase errors of a digitizer, with an experimental validation. Here, the attention will be focused on aspects not fully addressed by Crotti et al (2019). In particular, this paper will deepen the metrological characterization, explaining in details the evaluation of the uncertainty contributions, especially that due to the non-linearity of the comparator shown in Crotti et al (2019).…”

“…Here, the attention will be focused on aspects not fully addressed by Crotti et al (2019). In particular, this paper will deepen the metrological characterization, explaining in details the evaluation of the uncertainty contributions, especially that due to the non-linearity of the comparator shown in Crotti et al (2019). Moreover, in Crotti et al (2019), only the dependence of the absolute phase error on signal frequency and sampling frequency was shown, whereas, here, also the dependence on the signal amplitude and on the temperature are shown.…”

Optimised calibration programmes for comparators for instrument transformers

“…Usually, this is a pulse-per-second (pps) signal derived from a satellite navigation system. Since both the analogue signal and the external synchronisation signal are delayed in the comparator, separating the contributions of the analogue and the digital path is not trivial [14,15,16,17,18].…”