Road to the XBAR Filter

Speaker Information

Yasuhisa Fujii

Yasuhisa Fujii

Murata Manufacturing Co., Ltd.

Abstract

With the progress of wireless communication technology, surface acoustic wave (SAW) filters also have evolved significantly. In the late 1990s, the use of much heavier metals than conventional Al electrodes in IDTs was achieved through the development of quartz SH wave IF filters, and then by combining these with flat SiO₂ films, the world's first temperature-compensated RF filters (TC-SAW) were successfully developed. Additionally, by further thickening the SiO₂ film, boundary wave filters that are unaffected by surface effects and do not require additional packaging were realized. As the next step, we successfully developed the I.H.P-SAW filter with extremely high Q and low TCF by utilizing a composite substrate combining ultra-thin piezoelectric single-crystal films and a support substrate, thereby supporting the further evolution of wireless communication technology such as RF front end modules. Based on this composite substrate, a new type BAW filter combining IDT electrodes and a membrane, namely the XBAR filter, was proposed. Despite utilizing IDTs, the XBAR filter enables easy operation at frequencies above 3 GHz and achieves wide bandwidth characteristics than conventional AlN-based BAW filters. This technology has enabled the realization of high-frequency, wide-bandwidth filters such as those required for Wi-Fi 7 full-band filters.

Speaker Biography

Yasuhisa Fujii was born in Ishikawa, Japan in 1973. He received the B.S and M.S. degrees in science from Tohoku University in Miyagi, Japan, in 1995 and 1997 respectively. In 1997, he joined Murata Manufacturing Co., Ltd., Kyoto, Japan, where he has researched and developed surface acoustic wave devices used in the RF front-end circuits. He is the General Manager of the RF Filter Product Development Department. He recently led the development of the XBAR products. He is also serving as a member of IEC TC49.

Key Achievements:

  • Development of world's first temperature-compensated RF filters (TC-SAW)
  • Pioneering work on I.H.P-SAW filters with ultra-high Q and low TCF
  • Leadership in XBAR filter product development
  • Active contributor to international standards through IEC TC49