K-band tunable CPW phase shifters unit using Ba0.5Sr0.5TiO3 thin films

In order to design a high-efficiency phase array antenna or radar TR component, phase shifter with superior performance is in great request. A new structure k-band coplanar waveguide (CPW) type phase shifter using Barium Strontium Titanate (BST) thin films is demonstrated in this paper. Two ground planes and signal plane are deposited on the sapphire substrate, and BST is patterned on the gaps between signal plane and ground plane. The length, width, thickness of the whole device is 2mm, 2.5mm, 0.518mm respectively. The BST material has lots of special properties, such as high turning speed, low loss and tunable permittivity, which can be controlled by varying the DC-bias across the BST. Therefore, we can control the phase change of the device. Simulation results show that S11 is under -20dB around 20GHz and exhibits 74° phase shift at 20 GHz when BST's dielectric constant varies from 300 to 700. Due to the rapid development of the monolithic microwave integrated circuit (MMIC) technology and Tape-casting technology, the CPW using BST is easy to fabricate and has superior performance. It means CPW phase shifter unit is suitable for large-scale antenna array.