One-Dimensional Leaky Wave Antennas With Narrow Beam and Low Sidelobes

A new technique for designing one-dimensional (1-D) leaky wave antennas (LWAs) with narrow main beam and low sidelobe level (SLL) is proposed in this article. The presented method consists in connecting two open waveguiding structures designed to propagate a leaky wave with opposite phase velocities. The feed is positioned at the intersection plane, where the two branches are connected and are chosen to excite the propagative mode guaranteeing continuity of phase at said intersection plane. Thus, a unidirectional leaky wave will travel from one end of the structure to the other with a double exponential amplitude distribution. The provided analysis shows that, compared to conventional (single-sided) LWAs of the same length, and compared to bidirectional LWAs of the same length operating at an off-broadside angle, the beamwidth can be considerably reduced and the SLL can be concurrently reduced to a significant degree. Additionally, the directivity may be increased. To verify the presented technique and theory, a demonstrating prototype using split ring resonators (SRRs) and microstrip technology is designed, fabricated, and measured. A single-sided 1-D LWA is also fabricated and measured for comparison purposes. The experimental results confirm the proposed approach.