Evaluation of Detection Response of an Electric Field Probe to AM Signals Using Equivalent Circuit Model

To improve the measurement uncertainty for amplitude modulation (AM) signals measured using an electric field probe loaded with diodes, the effect of the nonlinearity of the probe on its detection response to the AM signals was investigated using an equivalent circuit model. First, the equivalent circuit parameters for simulating the electric field probe were estimated using approximate expressions of the probe with continuous wave (CW) signals. Then, these parameters were assigned to the equivalent circuit model to simulate AM signals. The detection response to the AM signals was examined using the probe gain. It was confirmed that the probe gain of the AM signals considerably deviated from that of the CW signals of the same power in the high-power-signal region. Moreover, it was also confirmed that the probe gain increases as the modulating frequency of the AM signals increases.