Design and Analysis of Miniaturized Hybrid Coupler at 900MHz using Stub

Abstract

The branch line coupler is the most passive component that has abundantly of wireless applications in modern communication and microwave systems. It has the advantage of small size, light weight, simple manufacturing, easy integration and high-performance device that is used to divide or combine power simultaneously. In order to obtain miniaturization, each section of transmission line in the conventional quadrature coupler which has electrical length of 90⁰ was replaced by equivalent small sections of transmission line connected in series. The result show that the size of the proposed coupler is reduced by 50% compared to the conventional design.  The couplers are mostly used in the design of microwave and RF devices such as balance amplifiers, mixers, phase shifters, antenna array, frequency discriminators and many other applications. In this study, the hybrid coupler is design for 0.9GHz with impedance (Z₀) 50Ω, and substrate material used in this work is Rogers RT5880 lossy with dielectric constant ξ_r= 2.2, with thickness 0.78mm, which is useful for cellular telephone network. Simulation is done by Computer Simulation Technology (CST) microwave suit studio software.