Short Pulse Measurements by Field Sensors with Arbitrary Frequency Response

Abstract

A calibration procedure for the characterization of E-field sensors is presented. It is based on the use of a simple structure for the generation of a known field distribution, the TEM-horn cell: in particular, the unwanted effects of the cell open termination are removed by a proper time domain gating of the sensor response. The achieved sensor transfer funct ion (amplitude and phase) allows the measurement of very fast transient field (e.g. radiated fields from an electrostatic discharge) through the application of a simple deconvolution procedure to the sensor output voltage time history. The proposed method is applied to a resonant dipole to demonstrate the possibility of measuring transient fields by employing whatever type of receiving structure, even with a complicated frequency behavior. Finally, the comparisons with theoretical field values and with the measurements, obtained by a commercially available active probe, are presented to validate the method. 60.1 Introduction The demand for the measurement of transient electromagnetic fields arises in several EMC and communications applications: electrical fast transient tests (EFf), , electrostatic discharges (ESD),2 and ultrawideband transmissions.' This is not an easy task because it requires sensors having flatness of the amplitude response over a wide frequency range (several gigahertz) , a minimum phase distortion , a proper sensibility, and reduced dimension s for minimum field perturbation for point measurements.t"" The realization of such sensors requires an accurate design and a considerable technological effort. In particular , it is possible to use purely derivative sensors , in order to model easily the relationship between the output voltage and the impinging field. To maintain their propert ies within the used frequency range, they are typically very small, and therefore suffer oflow sensitivity, limiting their use to extremely high 552