Measurement of electric field probe error for pulsed signals

Electric field probe performance is measured inside a calibration waveguide. The electric field probes based on diode detection are designed and calibrated for continuous signals. When measuring electric field strength of a pulsed waveform, performance degradation is expected. The degradation is measured in terms of measurement error. It is defined as electric field strength reading on the probe vs. actual electric field strength in the test volume of a calibration waveguide. Two such probes were measured. Test signals were pulsed (ASK) signals with fixed duty cycle of 1/10 and varying repetition frequency. The results show great differences among the two probes measured. One probe shows only slight degradation in terms of increased reading (positive measurement error) for high repetition frequencies. The second probe shows the same feature but of even greater extent, together with significant degradation for low repetition frequencies in terms of decreased reading (negative measurement error). The existence of such errors demands a great amount of caution during EMC measurements using diode-based electric field probes.