Design and Simulation of Quadrature Branch-Line Coupler for S Band Applications

Quadrature couplers constructed with the two coupled transmission lines that are set close together for energy transfers between the two lines. The design of branch-line coupler has been carried out for the band of 2.4GHz to 3.3 GHz. The applications of this band are in communication satellites, weather radar etc. Modified branch line coupler with compact size and wide bandwidth has been designed for replacing conventional quarter wave Branch Line Coupler presented in this work. The closed form of equations has been used for the coupler design. The simulation has been done in AWR software using RT Duroid substrate. The simulated results show the S parameter characteristics i.e. S11 & S22 are below -20dB while S21 & S31 are exactly at -3 dB. 90° phase difference between port 2 and port 3 is observed at the bandwidth ranges from 2.4 GHz to 3.3 GHz. The EM Simulation has been done to get the accurate results and verified with the AWR schematic. The theoretical analysis and practical results for designing of simple structure of branch line coupler has described thoroughly.