Miniaturized wideband branch-line hybrid coupler with capacitive effect and Defected Ground Structure (DGS)

Abstract

Background/Objectives: Branch-line hybrid couplers are used as components, in almost every Radio Frequency (RF) system, including power combiners and dividers. In this paper a 3dB miniaturized broadband branch-line coupler is designed and experimentally verified. Methods/Statistical Analysis: The new distributed capacitors which are placed within the empty space of the hybrid, minimize the size of the coupler. The ground of the structure is also defected by dumbbell shape parts to increase the impedance bandwidth. Findings: A prototype at 2.5GHz was designed and fabricated. The measurement results show that the bandwidth and isolation of the modified version are superior to the conventional 3dB hybrid coupler, also the measurement results confirmed that there is 2700 phase difference between output ports. The size of the fabricated structure shows 62% size reduction and also the measured bandwidth is 0.82GHz. Conclusion/Improvements: Miniaturized wideband branch-line hybrid coupler is a good candidate for development of a compact size and integrated microwave systems.