Length Reduction of a Short-Slot Directional Coupler in a Single-Layer Dielectric Substrate Waveguide by Removing Dielectric near the Side Walls of the Coupler

摘要

The authors have proposed a beam switching antenna composed of a Butler matrix and a slot array integrated on a single-layer dielectric substrate[l, 2]. Short-slot directional couplers are used to construct the hybrids and the crossing couplers in the Butler matrix. The length of the coupler is determined by the difference between the phase constants of the TE{sub}10 and TE{sub}20 modes in the coupled region. This paper proposes a method to reduce the coupler length by removing dielectric near the side walls as shown in Figure 4. The dielectric removal enhances the above-mentioned difference in phase constants and results in the reduction of the coupled region.