Full-Spectrum APD Measurement of Transient Interferences in Time Domain

Radiated transient interferences produce severe errors to digital communication systems. Conventional measurements defined in the electromagnetic compatibility (EMC) standards are not sufficient to predict the impact of this impulsive noise on the quality of a digital system, as measurements were originally defined to protect analogue communication systems. Measurement detectors and methods based on reaching the statistical of the interference have been studied as the best option to evaluate transient interferences. For a properly EMC emissions evaluation, an amplitude probability detector (APD) has been recommended as the best option, since APD results have been correlated with bit error probability. However, carrying out APD measurements using electromagnetic interference (EMI) receivers has strong inconvenience. One of the main limitations is that measurement can only be performed with the preset filters available at the EMI receiver, which sometimes are different from the communication bandwidths causing an incorrect estimation on the degradation produced. Another restriction is the elapsed time needed to acquire the statistical APD measurement at each frequency band. This document presents a methodology to obtain the APD measurement at any frequency band employing two single time-domain oscilloscope captures. The developed measurement method makes it possible to obtain the APD at any frequency band achieving as good results as the ones acquired from EMI receivers. To show the effectiveness of the time-domain method, an exhaustive validation study is presented, in which white Gaussian noise and several impulsive interferences are evaluated at frequencies from 50 MHz up to 1 GHz.