Experimental Verification of Microwave Phase Shifters Using Barium Strontium Titanate (BST) Varactors

In this paper, parallel plate varactor based phase shifter circuits using Barium Strontium Titanate (BST) thin films are presented. A cascade of 10, 15 and 20 parallel plate varactors were able to produce (150°, 258°, 297°), (218°, 381°,443°) and (227°, 402°, 464°) phase shift at (5, 10, 12 GHz) respectively. The 360° phase shift is achieved with small device size, low bias voltages (0-8 V), low leakage currents, low insertion loss and high figure of merit (FOM). FOM of 40, 33, 24 Degrees/dB is achieved with 10, 15 and 20 shunt varactors at 12 GHz respectively. The proposed circuit is very easy to fabricate which uses a CPW transmission line configuration and can be easily integrated with other circuits on chip.