Publication:
Development of six-port Interferometer using substrate integrated waveguide technique for radar-based sensor application
Development of six-port Interferometer using substrate integrated waveguide technique for radar-based sensor application
Date
2019
Authors
Tan Gan Siang
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Research Projects
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Abstract
In this work, the research is focused on the development of a six-port interferometer using Substrate Integrated Waveguide (SIW) technique where it can be worked as a component for the radar-based sensor. According to the past presented works in the open literature, most of the SIW six-port designs have an additional unused port and required a matched load termination. Besides, the performance of a conventional SIW six-port suffers from low isolation performance between its two input ports contributed by the conventional power divider component that is used to form the SIW six-port. One of the methods implemented in the past to improve the isolation performance is by introducing the isolation resistor between the output ports of the power divider. However, challenges arise when operating frequency increases as the appropriate size of the resistor are difficult to achieve. Therefore, a new configuration of the SIW six-port without unused port is proposed in this research. To improve its isolation performance without the use of a resistor, a new dual-layer power divider is proposed in this thesis. All the designed simulation is performed using CST Microwave Studio and the fabrication is done using Rogers 4003C substrate with a dielectric constant of 3.38. Since the key components of the SIW six-port are the power divider and hybrid couplers, hence the power divider and hybrid couplers are designed first using the single layer technique. All the components are designed at Ku-Band and K-Band, but for the demonstration of the prototypes, only the design at Ku-Band are fabricated and measured. For the dual-layer SIW power divider, the design is investigated at X-Band, Ku-Band and K-Band but fabrication and measurement are done at X-band only due to fabrication challenges on alignment and the existence of the air gap between substrate layers. The SIW coupler designed at Ku-band and has a wide bandwidth of about 31%. The SIW six-port without unused port is formed by single layer SIW power divider and SIW hybrid coupler, interconnected by delay transmission lines. It is successfully designed at the centre frequency of 14.5 GHz and has a bandwidth of about 20%. The dual-layer SIW power divider designed at 12 GHz and has high isolation of about 43 dB at 12.1 GHz. In the future work, the bandwidth of the SIW six-port can be improved by extending the length of SIW power divider transmission line and adding open circuit stub to improve the bandwidth of SIW power divider, consequently improve the bandwidth of the SIW six-port. The multilayer structure also has the potential to reduce the final dimension of the SIW six-port. For dual-layer structure, the research can be worked on SIW to slot-line transition to improve the isolation performance.
Description
Doctor of Philosophy
Keywords
Radar-based sensor,
Substrate Integrated Waveguide (SIW),
Six-port interferometer,
Six-port main components