IEICE Trans - A Half-Sized Post-Wall Short-Slot Directional Coupler with Hollow Rectangular Holes in a Dielectric Substrate

A Half-Sized Post-Wall Short-Slot Directional Coupler with Hollow Rectangular Holes in a Dielectric Substrate

Shin-ichi YAMAMOTO  Jiro HIROKAWA  Makoto ANDO

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C   No.7   pp.1387-1394
Publication Date: 2005/07/01
Online ISSN:
DOI: 10.1093/ietele/e88-c.7.1387
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Technologies of Microwave and Millimeter-Wave Devices Focusing on Miniaturization and Advancement in Performance with Their Applications)
Category: Passive Circuits
Keyword:
short-slot coupler,  length reduction,  Butler matrix,  post-wall waveguide,  dielectric substrate,  rectangular hole,

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Summary:
The authors realize a 50% length reduction of short-slot couplers in a post-wall dielectric substrate by two techniques. One is to introduce hollow rectangular holes near the side walls of the coupled region. The difference of phase constant between the TE₁₀ and TE₂₀ propagating modes increases and the required length to realize a desired dividing ratio is reduced. Another is to remove two reflection-suppressing posts in the coupled region. The length of the coupled region is determined to cancel the reflections at both ends of the coupled region. The total length of a 4-way Butler matrix can be reduced to 48% in comparison with the conventional one and the couplers still maintain good dividing characteristics; the dividing ratio of the hybrid is less than 0.1 dB and the isolations of the couplers are more than 20 dB.