Broadband 180¢X hybrid coupler

Abstract

This project requires making use of theories in the design, simulation and fabrication. Low phase variation and broadband operation frequency range of coupler are particularly important in wireless application as combiner or power divider. The 180° conventional coupler is narrow-banded and often large in size. In this new design, coupled-lines & Schiffman phase shifter are employed to improve the phase & bandwidth performance in the popular WiFi frequency band. The pattern ground plane technology, one of the practical methods, can increase coupling power to solve the fabrication problem using available fabrication methods and PCB material. A broadband 180°coupler, comprising of 2 sets of 90° 2-section coupled-lines and 180° multi-section double Schiffman phase shifter, has been devised, simulated, optimized, fabricated and estimated repeatedly. The coupler is made of microstrip-lines and coupled-lines on a substance with dielectric constant as 2.33. The dimensions are 7.2cm (L) x 5.0cm (W) x 1.57 mm (H). Moreover, a new coupler has phase error within 8°, coupling power coefficient equal to one-half, and 4 port’s return loss as lower than -10dB and the same impedance at all ports between the ranges of working frequency from 3.1GHz to 4.6GHz. It is found that the percentage bandwidth is 36.6%.