Emhemmed, Adel Saad
Performance enhancement of G-band micromachined printed antennas for MMIC integration.
PhD thesis, University of Glasgow.
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The objective of the work of this thesis is to design, fabricate, and characterise high performance micromachined antennas with fixed and reconfigurable bandwidth. The developed integrated antennas are suitable for MMICs integration at millimetre wave frequencies (G-band) on MMICs technology substrates (i.e GaAs, Si, InP). This work is done through a review of the scientific literature on the subject, and the design, simulation, fabrication and experimental verification, of various suitable designs of antenna.
The novel design of the antennas in this work is based on elevated antenna structures in which the radiator is physically micromachined above the substrate. The antenna design schemes offer a suitable method to integrate an antenna with other MMICs. Further, this method eliminates undesired substrate effects, which degrades the antenna performance drastically. Also in this work we have for the first time realized different micromachined antenna topologies with different novel feeding mechanisms - offering more degrees of freedom for antenna design and enhancing the antenna performance. Experimental and simulation results are provided to demonstrate the effectiveness of the proposed antenna designs and topologies in this work.
A new approach for fabricating printed antennas is introduced in this work to fulfil the fabrication process requirements. It provides a new method for the fabrication of 3-D multilevel structures with variable heights, without etching the substrate. Further, the height of the elevated structures can be specified in the process and can vary by several microns, regardless of the substrate used. This can be used to further enhance the bandwidth and gain of the antenna - avoiding substrate thinning and via holes, and increasing the fabrication yield. Thus, the elevated antenna can meet different application requirements and can be utilized as a substrate independent solution.
In this work we have introduced the concept of reconfigurable antennas at millimetre wave band. Also, we have investigated various aspects associated with lowering the pull-down voltage and overcoming the stiction problem of MEMS switches required for the proposed reconfigurable antennas. This was achieved by developing MEMS technology which can be integrated with MMICs fabrication process. Two novel reconfigurable elevated patch antenna topologies were designed to demonstrate the developed technology and their performances were discussed. The result we obtained from this work demonstrates the feasibility of MEMS reconfigurable printed antennas at G-band frequencies. This will open a new field in MMICs technology and increasing system integration capabilities and functionality.
The devolved technology in this thesis could be utilized in many unique applications including short range high data rate communication systems and high-resolution passive and active millimetre-wave imaging.
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