Frequency-Agile Ka-band Filters Based on Functionally Graded BST Thin Films

In this STTR program, Structured Materials Industries, Inc. www.structuredmaterials.com (SMI) and our University partners are developing compact, efficient, voltage-tunable, radio frequency (RF) filters. Although the Phase I and Phase II efforts are directed toward RF filters for use in the Ka band (26 to 40 GHz), the technology developed in this STTR project is equally applicable to many different products, operating over a wide range of RF and microwave frequencies. The tunable filters will have properties not possible using present technology, including; high speed, low loss, low insertion loss and excellent temperature stability. Our technical approach utilizes tunable dielectric thin films, based on barium strontium titanate (BST). We use functional composition grading to improve tunability and temperature stability of the films. We also use metallic acceptor doping to reduce dielectric losses. Phase I demonstrated technical feasibility of our approach, by producing BST film components with high tunability and excellent temperature stability. In Phase II, we will develop and demonstrate complete prototypes of the voltage tunable filters. We will also demonstrate the commercial manufacturing technology. In Phase III, we will implement and commercialize the filters and the tunable RF device technology, for a wide range of military and civilian applications.