Intermodulation Distortion Analysis of Microwave Tunable Filters Using Barium Strontium Titanate Capacitor and Varactor Diode

Abstract

This work presents a comparative study between adaptive filters for software-defined radio (SDR), using Barium Strontium Titanate (BST) tunable capacitor and varactor diode based filters. Since these filters can be used for jamming interference reduction in SDR implementations, their nonlinear behavior is of fundamental importance. This study is focused on exploring the intermodulation distortion (IMD) phenomenon in both filters. Thus, a comparison between these results will be made in the two configurations when using similar capacitive values. Although the BST capacitor-based filter allows higher tunability, it presents greater degree of nonlinearity, including memory effects like asymmetric IMD.