180° hybrid coupler implemented with 2x2 butler matrix

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Date
2019-06
Authors
Nor Amylia Binti Mohd Halmy
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Hybrid coupler is a four-port device where a directional coupler is designed to split power equally between two ports. Hybrid coupler can be used to decouple and increase the isolation between antenna ports. In this project, it is focus on how to design 180° Hybrid Coupler implemented with 2x2 Butler Matrix by using CST. The concept of transforming branch-line hybrid coupler into coupled-resonator network is presented in this project. The proposed of hybrid coupler with additional method with 2x2 Butler Matrix is to improve the isolation, size reduction, better terms of low production cost and good return loss. This project is focused on how to reduce the size of hybrid coupler so that it will obtain good S-Parameters. This design is fabricated using RO 4003C printed circuit board with dieletric constant, 𝜀(, 3.55 mm, thickness of substrate, H, 0.81 mm and thickness of copper, t, 0.035 mm. The design need to be operated at 2.4GHz. From the simulation and measured results, the 180° Hybrid Coupler implemented with 2x2 Butler Matrix nearly met the entire requirement needed such as return loss which is less than - 10 dB, isolation loss is nearly less than -5 dB. However, the isolation between ports is in the range frequency of 2.39 GHz to 2.54 GHz. It is still acceptable because the performance is not affected.
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