Effect of Substrate Dimensions on Zeroth-Order Resonator Antennas

This letter focuses on the design of electrically small transmission line zeroth-order resonator antennas (ZORAs). These antennas represent a known concept. However, previous works seem to neglect the size of the substrate. A small antenna that requires a large ground plane loses its competitive advantage. Thus, this letter studies the relation between substrate dimensions and the antenna properties on the example of a ZORA using e-negative transmission line (ENG TL). It was found out that antenna radiation properties deteriorate as the substrate is reduced. Thus, a simple measure based on use of metallic walls to overcome this issue is also introduced in this letter.