STANFORD UNIVERSITY
EE 350 RADIOSCIENCE SEMINAR
Professor Antony Fraser-Smith

Fall 2000-2001

Date: Wednesday, April 18, 2001
Time: 4:15-5:30 PM; Refreshments at 4:00 PM
Location: Bldg.200, Rm.34


Micro-Machined Bulk Acoustic Wave Resonators (FBAR) for Cellular Telephone and other Microwave Device Applications

Dr. John D. Larsen III
Agilent Laboratories

Abstract

Cellular telephones are a mass marketed form of microwave radio communication systems, which makes them interesting both to the technologist and the industrialist. In the block diagram of any radio system, one inevitably finds highly integrated semiconductor circuits such as amplifiers, mixers, and oscillators, as well as band pass filters and high Q resonators liberally sprinkled throughout. To meet the need for ever smaller, higher performance cellular phone systems, Agilent is developing a dramatically new miniaturized bulk acoustic resonator technology that provides filters of exceptionally small size and low cost, as well as an insertion loss in the 1 to 2 dB range, good power handling capability, high out-of-band rejection, and low temperature coefficient. The major advance has been to couple thin film, bulk acoustic wave resonator (FBAR) and filter design methods with silicon based micro machining technologies to produce wafer scale, mass produced components.

A major use of the FBAR resonator is to build band pass filters with center frequencies around 1.9 GHz, fractional bandwidths of 3 to 5%, and minimum insertion loss ~1 dB. The design of such filters will be summarized, along with examples of actual devices, and some mention of the problems in mass producing them. Finally, the process of developing a viable use for such filters will be described, with a PCS band duplexer as a current example. The duplexer is a device that allows simultaneous Transmit (TX) and Receive (RX) in a cellular telephone. FBAR duplexers are being built that rival the specifications for traditional ceramic monoblock units, yet occupy 1/10 the volume, a major advantage for cellular phone manufacturers who ever strive for handsets suitable for pygmies! Come to hear how an idea from the research laboratory is nurtured into to a major business opportunity at Agilent, and how the contributions of many dedicated workers make that possible.