Analysis and Design of MEMS-Based Multi-Functional Aperture Antennas

  • Author / Creator
    Moghadas, Hamid
  • Future antennas consist of low-profile smart multi-functional radiating apertures which support multi-beams of multi-bands with multi-polarizations. They can scan the surrounding environment, choose the band of interest and generate the required beam shape. Such antenna can be utilized in numerous emerging applications such as vehicular satellite communication, software defined and cognitive radio, and also next generation of mobile networks (5G). This thesis develops MEMS-tunable orthogonally-polarized dual-band Resonant Cavity Antennas (RCA) and also reflectarrays as platforms for future multi-functional aperture antennas. As an initial prototype, a high gain orthogonally polarized dual broadside beam RCA is designed, fabricated and measured. Also, an equivalent transmission line model and a design flow chart are extracted for the RCA in order to understand the dual band beam forming and facilitate the quick design. Furthermore, the independence and the arbitrary separation of the operating bands is demonstrated. Next, a MEMS-tunable RCA is designed, fabricated and measured with an upper band vertically polarized broadside beam and a lower band horizontally polarized beam which is switched among all possible beam shapes of leaky wave antennas, i.e., broadside, symmetric conical, and also an asymmetric single beam which is either frequency scanned or steered at fixed frequency. Traditionally, a Full Phase-Gradient (FPG) Partially Reflective Surface (PRS) has been used in an RCA for generating beams off broadside. A FPG-PRS is a non-uniform aperture where a continuous phase gradient is applied between adjacent cells in the whole PRS. Here, the novel configuration of Half Phase-Gradient (HPG) PRS was offered where the phase gradient is applied between adjacent cells in half of PRS in order to utilize the inherent leaky wave phase progress inside the cavity. The HPG-PRS provides enhanced scan profile, faster real time tracking, and reduced DC power consumption which are all critical in wireless, space and military applications. Furthermore, a novel model is extracted for calculating the radiation of such RCAs with non-uniform aperture and verified by comparison with measurements. This model can be applied to any leaky wave antenna with arbitrary unit cell shape and periodicity. Finally, the unit cell required for the beam shaping RCA is realized by hybrid integrated MEMS switches. In the field of reflectarrays however, a phase tunable low loss double slotted patch reflective unit cell is designed and simulated for operation at 12 GHz with vertical polarization and 14 GHz with horizontal polarization for Ku band mobile satellite communication. The phase tuning is facilitated using an array of switches across both slots in order to dynamically control the equivalent slot length. A monolithic custom fabrication process is developed for fabrication of the proposed reflectarray unit cell with MEMS switches. Finally, this unit cells is measured inside a waveguide setup with DC bias pads to verify the phase tuning.

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  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.