Novel compact inverted U‐shaped directional coupler using parallel dual transmission lines technique

Abstract

ABSTRACTA novel compact design of a 3‐dB inverted U‐shaped directional coupler using dual parallel transmission lines on double layer substrates is presented in this article. Dual parallel transmission lines technique is used as a replacement of the conventional single transmission line. Hence, a smaller size and wider bandwidth of directional coupler is successfully achieved. The proposed coupler is highly adaptable to various microwave applications for microwave circuitry such as the Butler Matrix (BM) beamforming network. The reduction in size gives better flexibility for the integrated structure of BM system. The proposed 2.45‐GHz coupler successfully obtaining size reduction up to 40% compared to the rectangular multilayer directional coupler. In addition, 25% bandwidth performance was achieved. Dimension and S‐parameter performance comparison has been made between the proposed coupler which use dual parallel transmission lines technique in multilayer structure and rectangular multilayer coupler. The measurement results are in good agreement with simulated ones in terms return loss, coupling, through and isolation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:251–256, 2014