Performance function for time-jittered equispaced sampling wattmeters

This paper evaluates the effect of time-jitter in the equally spaced sampling wattmeters on the hypothesis of equal effects in the two channels and a jitter uncorrelated with the input signals. It is shown that time-jitter, which is a random fluctuation with respect to the nominal sampling time, introduces a frequency limitation which is evaluated together with that due to the sampling strategy and filtering algorithm. The theoretical results are compared with the simulated one

The effect of time-jitter in equispaced sampling wattmeters

This paper evaluates the effect of time-jitters in the equally spaced sampling wattmeters on the hypothesis of jitters uncorrelated with the input signals. The general case of two distinct time-jitters is considered, one common to the two channels and the other different for each one of them. The performance of the wattmeter has been evaluated by considering the asymptotic statistic parameters of the output. It has been shown that the different time-jitters introduce a bias and that both time-jitters contribute to the variance of the output. In any case, time-jitters introduce further bandwidth limitations which must be taken into account in the wattmeter accuracy evaluation. The theoretical results have been compared with simulated and experimental findings. Experimental results were obtained with a prototype in which both common and different time-jitters were separately added to the equally spaced sampling instants of the two input channels. In both cases, all the results were in good agreement with theoretical expectation

Recursive random-sampling strategy for a digital wattmeter

A recursive random-sampling strategy is proposed for the implementation of a digital broadband wattmeter. In this strategy each sampling instant is obtained by adding to the preceding one a predetermined constant lag plus a random increment. In order to correlate the measurement uncertainty to the bandwidth, the asymptotic mean-square error arising from the sampling strategy and the filtering algorithm is evaluated and analyzed; it has been shown that the proposed sampling strategy does not limit the bandwidth of the instrument if an appropriate statistical distribution of the random increments is selected. The theoretical results are compared with those obtained by simulating the measurement proces

Implementation and performance evaluation of a broadband digital harmonic vector voltmeter

A broadband digital harmonic vector voltmeter proposed previously and studied theoretically by the authors was implemented using a special-purpose, random sampling strategy, to avoid the bandwidth limitations due to the finite conversion time of the sample-and-hold and analog-to-digital-conversion (S/H-ADC) devices. The experimental results have shown that the bandwidth of the instrument is not limited by the finite conversion time of S/H-ADC devices, since good accuracy can be achieved even when the average sampling frequency is much lower than the signal bandwidth. The amplitude and phase uncertainty, with sinusoidal test signals up to 1 MHz and an average sampling rate of 10 kHz, was found to be lower than 3% and 0.03 rad, respectively. For more careful testing of the broadband performance of our instrument, we also carried out two-frequency, variable order harmonic measurements, which showed good accuracy (amplitude error less than 1.5% and phase error less than 0.03 rad) with harmonics up to 300 kHz. Reasonable accuracy (i.e., sufficient to correctly reconstruct the actual signal waveform) was also found with a highly distorted square-wave signa