The Effect of Diode Response of Electromagnetic Field Probes for the Measurements of Complex Signals

Diode detectors present inside electromagnetic field probes are typically calibrated for linearity using continuous sinusoidal waveforms (CW). In this paper, it is shown that CW linearization is not adequate for the measurement of complex wireless communication signals with high peak-to-average power ratios. While previous analog and digital communication signals (1G and 2G) can be more easily corrected for linearity, newer 3G and 4G communication protocols employ complex modulations with stochastic signal envelopes. As a result, proper linearization depends on the diode response and signal characteristics, and large errors results if CW linearization is used. The errors introduced when measuring such signals with probes employing CW linearization are quantified in this paper. A numerical model of the diode response is provided and validated against measurements. Errors due to CW linearization can exceed 2 dB, whereas linearity errors within 0.4 dB are attainable using the proposed calibration procedures for even increased dynamic ranges.