Backward-wave directional coupler with complete coupling and broadband using conventional microstrip and 1D mushroom structure

Abstract

A new type of backward-wave coupled-line directional coupler with complete coupling and broadband which is composed of conventional microstrip and a ID mushroom structure, is proposed. The ID mushroom structure is employed for a double negative (DNG) trans-mission line. The coupler exhibits unusual characteristics such as complex propagation. The Complex propagation constant of the coupled mode enables strong coupling elite to exponential field decay. The performance of the proposed coupler is verified by c- and pi-mode analysis, full-wave simulation, and measurement. The measured coupling level of -0.5 dB with 3-dB fractional bandwidth of 35% and high directivity of 30 dB is achieved. (c) 2006 Wiley periodicals. Inc.