Low Cost Ferroelectric Thin Films for Frequency-Agile Microwave Filters

This SBIR Phase II project is stimulated by the explosive growth of the wireless telecommunications industry. There has recently been a great deal of interest in designing tunable RF devices that utilize ferroelectric thin films for their electronicproperties. Specifically, barium strontium titanate (BST) thin films are being used to develop new classes of tunable microwave devices, including phase shifters and frequency-agile filters. Today's commercial and military wireless systems are limited incapability due to the use of fixed-tuned filters in receiver front-ends and transmit output stages. This project will develop frequency-agile filters using BST thin films deposited using Microcoating's proprietary CCVD process. These filters, operatingin the 2GHz cellular band, will be capable of changing their operating frequency through the application of a DC control voltage. Currently, ferroelectric devices suffer from the need for large tuning voltages (100v), which are not readily available inmost commercial applications. MicroCoating Technologies (MCT) proposes a unique electrode design that permits the separation of the DC bias voltage from the microwave AC signal, enabling high tuning ranges with bias voltages of less than 5v. Lastly,temperature compensation of the BST film will be accomplished over the commercial temperature range.