Parallel Coupled Microstrip Couplers Compensated with Periodic Floating-Conductors on Coupled Edges

Tadashi KAWAI
Yoshihiro KOKUBO

IEICE TRANSACTIONS on Electronics   Vol.E91-C    No.5    pp.780-787
Publication Date: 2008/05/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.5.780
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
artificial coupled-line,  directional couplers,  microstrip couplers,  parallel coupled lines,  periodically loading,  

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This paper presents a new quarter-wavelength microstrip coupler compensated with a periodic sequence of floating metallic strips in the slots on the inner edges. After describing the characteristics of the coupled-line, as an example, a 15-dB coupler is designed and a high directivity of 30 dB or more in theory is obtained over a full band of a single-section coupler. Next, couplers with various coupling factors are designed, and the usefulness for very loose coupling is demonstrated. Furthermore, a three-section coupler is designed to show the effectiveness in a wide frequency range. The validity of the design concept and procedure is confirmed by electromagnetic simulations and experiments.