Design of a Compact Omnidirectional Leaky-Wave Antenna Fed by Higher Order Mode

This article presents a novel leaky-wave antenna (LWA) based on a dielectric-filled rectangular waveguide (RWG) and fed by a higher order mode. The proposed quasi-uniform LWA has a compact configuration that is suitable for microwave applications, featuring the omnidirectional radiation patterns and low cross-polarization. In the frequency band of interest, the higher order mode, i.e., the TM 11 mode, performs as a fast wave in the proposed quasi-uniform LWA, radiating via the transverse slots etched on the walls. The advantage of the TM 11 mode for LWA applications is analyzed and demonstrated. This higher order mode is excited via a mode convertor from an inline coaxial line to the dielectric-filled RWG. For the reduction in sidelobe levels at high frequencies, −25 dB Taylor amplitude distribution is applied to the etched slots. The dielectric-filled LWA with the inline coaxial feeding is fabricated and measured. The measurement is consistent with the simulation, showing frequency-driven beam-scanning capability with low cross-polarization in the elevation plane. The simulated and measured radiation patterns in the azimuth plane illustrate the omnidirectional radiation patterns and thus confirm the radiating performance of the TM 11 mode in the proposed LWA. The advantages of the scanned beams and omnidirectional radiations are promising for radar systems.