Microwave phase shifters based on sol-gel derived Ba0.3Sr0.7TiO3 ferroelectric thin films

In this paper, we report on the performance of microwave phase shifters implemented on sol-gel derived Ba_0.3Sr_0.7TiO₃ (BST) thin films. Coplanar waveguide (CPW) phase shifters, loaded-line phase shifters, and reflection-type digital phase shifters have been realized on a single alumina substrate covered with a 300 nm-thick BST film. The performances of different types of phase shifting cells are compared. It is shown that the optimally designed digital phase shifters have better performance although the digital nature of the operation limits the range of their possible applications. A figure of merit FoM -100/dB at f -= 20 GHz and E = 400 kV/cm is demonstrated for the one-bit digital phase shifter.