Wideband Electric Field Probe Lower Cut-off Frequency Determination

A wideband electric field probe based on the diode detector connected to a low-pass filter is analyzed here. This circuit is analyzed using a linear-nonlinear analytical approach, and the transfer function is given for small and large signals. It is shown that the flat response is expected above the cut-off frequency, which is defined differently for small and large signals. The cut-off frequency depends on the diode zero-bias resistance for the small signals, and on the reverse-bias resistance for the large signals. If the probe should work for both types of input signals, large and small, the single frequency bandwidth declaration of the probe could be ambiguous or incorrect. The cut-off frequencies for large and small signals should be as near one another as possible. That could be achieved by balancing the overall circuit resistances in different regimes with the right choice of the input resistance of the low-pass filter.