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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Abstract
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.