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Ferroelectric (FE) Barium Strontium Titanate (Ba (1-x) Sr x TiO 3 , BST) thin film varactor technology is applied to the antenna miniaturization and reconfiguration successfully. CPW square-ring slot antenna is used as a design example, and antennas with and without integrated BST varactors were fabricated and characterized. Including the total ground, the size of miniaturized antenna is 0.12λ 0 ×0.12λ 0 which is reduced by 31% compared with antenna without the BST varactors. Moreover, the frequency of the miniaturized antenna with the BST varactors is reconfigurable from 5.8GHz to 6.1GHz with a low DC biasing voltage of 3V. Both E-plane and H-plane patterns were measured for the antennas. Fabrication details and measurement setup are also presented.Index Terms -Ferroelectric, thin film, antenna miniaturization, reconfigurable antenna, coplanar waveguide (CPW), ring slot antenna, varactor loading, high permittivity material.

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Vanadium dioxide (VO 2 ) thin films have unique insulator to metal transition above the critical temperature of 72 ºC. In this research, VO 2 thin films were deposited on a sapphire substrate for thermally controllable RF/microwave switching devices with integrated heating coil. The VO 2 thin film based devices showed insulator performance at room temperature and metallic state (low resistive phase) at 80 ºC. Switching devices designed using a VO 2 series varistor showed good isolation (< -30 dB) and low insertion loss (> -5 dB) up to 20 GHz.