Time: 8:30-9:15，Oct.26, 2023，Thursday

Speaker:

    Prof. Ken-ya Hashimoto (Fellow of IEEE)

University of Electronic Science and Technology of China

Abstract:

So many resonators based on surface and bulk acoustic wave (SAW/BAW) technologies are installed in the RF front-end of current smartphones as filters, duplexers, and multiplexers. Now most of all RF functionalities have been realized by CMOS LSI, and thus various attempts were examined to get rid of these devices. However, they were failed at least until now. Why? The biggest obstacle is non-linearity. RF SAW/BAW resonators are quite linear and this is the biggest reason why they are not replaceable with the other technologies. Nevertheless, further linearity improvement is strongly requested. This is because stored energy density becomes higher and higher due to recent trend of increase of transmit RF power and downsizing. Introduction of carrier aggregation made this problem more sevire.

Self-mixing of transmit signals may be cancelled in some extent by circuit design and/or digital signal processing. However, they are helpless for mixing with unknown in-coming jammer signals.

Furthermore, RF SAW/BAW devices must fullfil varius tough specifications in addition to the linearity: low insertion loss in the passband, good out-of-band rejection, narrow transition bandwidth, small passband ripples, temperature stability, power durability, small size, and low price.

This talk reviews current status of RF SAW/BAW devices used in mobile communications. Typical device performances are presented, and discussions are given on why such tough specifications are given. Nonlinearity in RF frontend and its impact to high-speed mobile communications are detailed.

Bio:

Ken-ya Hashimoto was born in Fukushima, Japan, in March 2, 1956. He received the B.S. and M.S. degrees in electrical engineering from Chiba University, Chiba, Japan, in 1978 and 1980, respectively, and the D.Eng. degree from the Tokyo Institute of Technology, Tokyo, Japan, in 1989.

He joined Chiba University as a Research Associate in 1980 and retired there as a Professor Emeritus in 2021. From 2013 to 2015, he was the Director of the Center for the Frontier Science with Chiba University. Right after retirement, he moved to the University of Electronic Science and Technology of China (UESTC), Chengdu, China, as a Professor. He had Visiting Professor/Researcher positions in various institutions, such as the Helsinki University of Technology, Espoo, Finland, in 1998, the Laboratoire de Physique et Metrologie des Oscillateurs, CNRS, Besancon, France, in 1998/1999, Johannes Kepler University, Linz, Austria, in 1999 and 2001, the Institute of Acoustics, Chinese Academy of Science, Beijing, China, from 2005 to 2006, UESTC from 2009 to 2012, and the Shanghai Jiao Tong University, Shanghai, China, in 2015.

He served as a Guest Coeditor of the IEEE Transactions on Microwave Theory and Techniques Special Issue on Microwave Acoustic Wave Devices for Wireless Communications in 2001, and a Publicity Cochair of the 2002, 2015 and 2021 IEEE International Ultrasonics Symposia, an International Distinguished Lecturer of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) Society from 2005 to 2006, an Administrative Committee Member of the IEEE UFFC Society from 2007 to 2009 and from 2014 to 2016, a Distinguished Lecturer of the IEEE Electron Devices Society from 2007 to 2009, and a General Cochair of the 2011 and 2018 IEEE International Ultrasonics Symposia.

He received IEEE Fellow in 2005 (now IEEE Life Fellow), the Ichimura Industrial Award from the New Technology Development Foundation for Development of Optimal Substrate 42-LT for Radio Frequency Surface Acoustic Wave Devices in 2015, The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology for Research on High Performance Radio Frequency Surface Acoustic Wave Devices in 2018, and the Distinguished Service Award from the IEEE UFFC Society in 2019.

His current research interests include simulation and design of various high-performance surface and bulk acoustic wave devices, acoustic wave sensors and actuators, piezoelectric materials, and RF circuit design.