Measurement of Electric Field Probe Response to Modulated Signals Using Waveguide Setup

Electric field probes based on diode-loaded short dipoles bear an inherent limitation of use concerning the signal waveform. When measuring signal waveforms other than sinusoidal, probes can show a considerable measurement error. Although this error has been recognized before, its importance is growing lately due to expansion of new modulation schemes. Therefore, a convenient measurement setup and procedure is needed to examine and measure such probe errors for various types of signals. An example of a waveguide-based measurement setup is presented in this letter. The advantage of the proposed setup is the ability to achieve high field strength in the test volume suitable for field probe testing, using small to moderate output power.

I. Introduction

Wideband electric field probes have been widely used in electromagnetic measurements since the 1980s [1]–[3]. Field probes are used mainly in electromagnetic compatibility (EMC) labs to verify the field strength inside an electromagnetic chamber or for radiation hazard measurements. The most common type is the electric field probe based on diode-loaded short dipoles. Primary analysis of such a probe is given by Kanda in [1], and a revisited analysis is given in [4]. The initial analysis is based on a sinusoidal incident field. It has been noticed, even in the early days [5], that the probes may exhibit errors when measuring nonsinusoidal signals or multiple signals. This kind of error is also mentioned in relevant standard referring to the use of field probes for measurements of radio frequency electromagnetic fields with respect to human exposure [6].