LOW THIRD-ORDER INTERMODULATION DISTORTION IN Ba_0.6Sr_0.4TiO₃ THIN FILM INTERDIGITAL CAPACITORS

Abstract

Abstract-A new method for the theoretical analysis of the thirdorder intermodulation distortion (IM 3 ) in barium strontium titanate (BST) thin film interdigital capacitors (IDCs) on r-plane sapphire substrates is presented. Two circuit topologies -the dual and series dual BST varactor circuit -are proposed and their theoretical models along with simulated and measured results are presented. Low IM 3 is demonstrated and experimentally verified. By proper selective biasing, very low nulls are observed in both dual and series dual BST varactor circuit topologies which indicate minimum distortion. The measured first nulls are achieved at ±13 V and ±20 V for the dual and series dual topologies respectively. These results demonstrate the potential of incorporating these highly linear BST varactors in silicon on sapphire (SoS) applications.