Enhanced Design of Two-Section Microstrip-Slot Branch Line coupler with the overlapped λ/4 open circuited lines at ports

Abstract

This article presents the design of enhanced two-section microstrip-slot branch-line coupler (BLC) with tight coupling of 3-dB over frequency of 2–5 GHz. Initial design is based on a common two-section microstrip BLC. To enhance the bandwidth performance, an overlapped λ/4 open circuited line is adopted to each port. Furthermore, each of BLC branch is formed by a microstrip-slot line. Shunt branches of the designed BLC are bended to reduce its size, where 31 % size reduction has been achieved. The effect of proposed techniques and the performance of the designs are observed and compared. The designs and analysis are performed with the use of full-wave electromagnetic simulation software package, CST Microwave Studio. The proposed BLC is fabricated, and its wideband performance is verified.