An Accurate Circuit Model for Input Impedance and Radiation Pattern of Two-Port Loop Antennas as E- and H-Probe

In this paper, a simple but very accurate circuit model for two-port (split) loop antennas typically used for direction finding in the HF-band is presented. The circuit model consists of lumped elements and can be used to accurately estimate the input impedances and received voltages of two-port loop antennas in receive mode. It is shown that the same circuit model can be reduced to predict the input impedance behavior of a single-port loop antenna with much more accuracy than the existing transmission line and lumped element models over a wide frequency range. The model is shown to be valid for frequencies up to a point where the loop circumference is about a wavelength. The same circuit model in receiving mode can provide the 3-D radiation pattern of the antenna.