Investigation of Antenna Edge Treatments and Ground Plane Coupling Behavior

Abstract

Guided wave structures can perform as broadband antenna elements through the use of a gradual impedance transformation. The impedance match is typically created through gradual structural changes to match the impedance of the guide to that of free space. For parallel plate waveguide, it has been shown that serrating the edge of one of the conductors at the truncation between the waveguide and freespace can minimize reflection at that plane and present a broad impedance match between the waveguide and freespace. This method, however, is most effective when the parallel plate and serration are an appreciable size of a wavelength. This work presents potential alternative edge treatment designs other than the triangular serration for better impedance matching and radiation performance, particularly at small electrical sizes. This study extends the insights gathered from the edge treatment investigation to their potential in inducing ground plane currents when included in an antenna design that is placed over a large ground plane. With the ability to excite ground plane currents on metallic structures, the investigated antenna can improve the performance of electrically small antennas through strategic placement. This antenna is what is used as the feeding mechanism for the proposed edge treatments so their behavior is accurately characterized.