New tunable microwave Ba0.6Sr0.4TiO3/MgO phase shifters using interdigital capacitors and slit-inductors

Abstract

In this paper, we report on the role of slit-inductors in notably improving phase shifting capabilities in Ba0.6Sr0.4TiO3 (BST) tunable phase shifters utilizing interdigital capacitor (IDC) structure. The IDC-based coplanar waveguide (CPW) phase shifter with slit-inductors fabricated on (100) oriented BST films deposited on MgO substrates exhibits a much enhanced phase difference of 35.52 degrees, as compared to that (25.230 degrees) of the IDC-based phase shifter at 12 GHz. The figure of merit (FoM) of the IDC-based phase shifters with slit-inductors shows larger value of 43.60 degrees/dB as a result of improving phase shifting while retaining an appropriate insertion loss compared to that (35.670 degrees/dB) of the IDC-based phase shifter without slit-inductor. This work demonstrates potential use of slit-inductors for producing high-performance CPW based BST tunable elements in microwave circuit.