Illinois ECE graduate student wins IUS Best Student Paper Award


Joseph Park, Illinois ECE

Liuqing Gao
Liuqing Gao

In the annual IEEE International Ultrasonics Symposiums (IUS 2020) held Sep 7-11, 2020, Illinois ECE PhD student Liuqing Gao won the student paper competition for her paper entitled “A 14.7 GHz Lithium Niobate Acoustic Filter with Fractional Bandwidth of 2.93%.” The paper was authored by Gao, Illinois ECE postdoctoral researcher Yansong Yang, and Illinois ECE Associate Professor Songbin Gong, Intel Alumni Fellow in Electrical and Computer Engineering. 

IEEE IUS is one of the world’s pre-eminent forums for the latest advances in Medical ultrasonics, sensors, physical acoustics, microacoustics, and transducers. IUS 2020 has more than 1,900 researchers attending from around the world. The committee selected 18 finalists of five technical groups, which ranked the top 4% of all student submissions. Finalists are evaluated based on their clarity of presentation, depth of knowledge, degree of contribution to the project, and relevancy of the work to the field, and Liuqing is the winner of Group 4: Microacoustics:  SAW, FBAR, MEMS.

Gao's work presented the first demonstration of a wideband hybrid monolithic acoustic filter in the Ku-band that overcomes the electromechanical coupling on the fractional bandwidth of the conventional ladder topology acoustic filters. The filter combines electromagnetic and acoustic structures to take the respective advantages of the wideband, high Q, and compact sizes.

Optical image of the fabricated device
Optical image of the fabricated device

With the rapid expansion of the telecommunication market, frequency bands below 10 GHz have become overcrowded.  Scaling the communication systems to higher frequencies is of more importance for future mobile systems. Acoustic filters are widely adopted in mobile RF front-ends due to their high Qs and compact footprints, which face many challenges in scaling and have drawn a lot of research attention. This work provided a monolithic solution to the limitations faced by the State-of-the-Art technologies when scaling to higher frequency ranges, which has a strong potential for the RF front-ends in the 5G handheld applications.

Their work also solved the challenge of lacking miniatured filters in the Ku-band by utilizing the 5th order overmoded MEMS/acoustic resonators. Furthermore, their research provided a monolithic solution to the challenges in the loss of electromechanical coupling with overmoding and the need for a large offset between the resonances of the component resonators to construct a filter with wide passband.

The authors wish to thank the NSF SpecEES program for funding support. The authors also would like to thank the staff of the Nick Holonyak Micro and Nanotechnology Laboratory and the Micro-Nano Mechanical System Cleanroom at the University of Illinois at Urbana-Champaign where the devices were fabricated.

Gong is also affiliated with the HMNTL