Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535386
Title: Micromachined millimeter wave circuits
This thesis presents the design and characterisation of millimetre-wave Butler matrix beamforming circuits at 63 GHz. A micromachining technique is used to fabricate the tiny structures. The ability to manufacture the circuits at this frequency may benefit to the development of intelligent transport system (ITS) communication and sensing systems. All components that build the Butler matrix beamformer are designed to fit the thick SU-8 photoresist micromachining technology, where structures are built by bonding together five layers of metal coated SU-8. The matrix is constructed using air filled rectangular coaxial lines. The dielectric losses are avoided by having air filled structure, however the suspended lines need supporting system. Therefore, stubs are placed in the circuits to hold the suspended lines. In order to transfer signal from the Butler matrix to the antenna, a transition is necessary. A rectangular coaxial line to ridge waveguide transition is designed to feed the H-plane horn antenna and the ridge waveguide slot antenna. The novelty of this work is in both the design of new microwave structure and also in the demonstration of millimetre wave structures in micromachined form using SU8 resist. Four new microwave structures are (1) a back to back rectangular coaxial line to ridge waveguide transition, (2) an H-plane horn antenna, (3) a ridge waveguide slot antenna, and (4) a Butler matrix with a patch antenna array. These and other structures have been built and tested and finally the selection put together to form a new type of Butler matrix. The compatibility of the designs to the fabrication method has been demonstrated. The transition return loss is better than -12 dB from 60 GHz to 90 GHz and has been proven to work with integration to the horn and the waveguide slot antenna. The Butler matrix with a patch antenna array exhibits the forming of the beams at $$\pm$$17$$\circ$$ as expected from the theoretical calculation.