Analog tunable matching network using integrated thin-film BST capacitors

This paper presents an electronically tunable impedance transformer and matching network for RF applications, utilizing thin-film Barium Strontium Titanate (BST) tunable capacitors in an integrated-passive network on sapphire. The impedance transformer can be electronically varied from a 4:1 to 2:1 transformation in a 50 Ohm environment. A slight modification of this circuit is shown to provide a match for a highly-reactive integrated antenna allowing the antenna to be used with improved efficiency from 420MHz to 500MHz. ACPR measurements are presented on the latter network showing ACPR1 of >50dBc at 27dBm drive power