High Directivity Directional Coupler using Metamaterial

Abstract

In this paper, a novel uniplanar directional coupler using left-handed transmission lines is proposed. Short microstrip parallel coupled lines and asymmetrical delay line pairs make multi-sectioned coupler enhance the directivity as well as the coupling. Each delay line pair consists of a right-handed transmission line and a lumped left-handed transmission line. Furthermore, a Lambda/12 coupled line for the coupled line section makes the design area compact. The designed 3-section 18 dB coupler is measured at the center frequency of 2.0 GHz, which shows good agreement with the simulation result