Remote Characterization of Small Antennas Using Waveguide

A new method is introduced for remote (i.e., cable-less, indirect) estimation of radiation efficiency and input impedance of electrically small antennas (ESA) by placing them inside a rectangular waveguide with dominant TE
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mode. The estimation is carried out using the scattered field from ESA when it is terminated with three different impedances. Input impedance and radiation efficiency are then calculated using the obtained complex scattering values. In addition, the paper discusses the relationship between the obtained ESA parameters inside the waveguide to those in free-space. The method has been verified by simulations on two different ESAs in the frequency range of 2 to 3 GHz.