Development of CAD for Microwave Hybrid Branch-Line Coupler Design Using MATLAB-Based GUI

This paper presents the development of user-friendly MATLAB-based computer-aided design (CAD) tool for microwave hybrid branch-line coupler design. The CAD is capable of predicting the characteristic impedance and the dimensions of the branch lines. In addition, the CAD also shows the output results in graph of S-parameters versus operating frequencies. The CAD can be used to design three kinds of branch-line couplers, namely single, double, and three sections branch-line couplers. The important analytical formulations which are implemented in this CAD are briefly described. Those formulations are derived using ABCD matrix, transmission line principle, and even–odd mode decomposition techniques. Hence, this CAD has simple guide user interface (GUI) display and fast program running time compared to iterative solution or numerical-based CAD. The accuracy of the CAD output results is validated by comparing to measurement and simulation results obtained from commercial simulator.