CAREER: MEMS Reconfigurable Filters for Multi-Band Low-Power Radios

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

This CAREER proposal aims at the development of a single-chip reconfigurable MEMS filter platform for multi-band, multi-standard radios through fusion of acoustoelectrically amplified nano-mechanical filters and 3D tunable components. Reconfigurable filters can greatly enhance the performance and reduce the size of RF front-ends, and as such have received great attention for effective and low-power processing of the frequency spectrum. Despite their great promise, lack of integration and narrow frequency coverage of current reconfigurable filters continue to hinder their use in practical applications. In addition, current technologies have failed to reduce the size of filters without deteriorating critical performance metrics such as loss, power handling and termination impedance. To-date, a versatile and reconfigurable filter array platform does not exist in monolithic form, an important problem that has remained unsolved despite major advancement in MEMS. This proposal tackles the fundamental issues related to reconfigurable filter arrays and proposes a novel technique that offers frequency, bandwidth and amplitude tunability through integration of narrow-band acoustic filters with tunable lumped filters. These are believed to be the most prominent steps toward the realization of a single-chip multi-band lowpower radio. Intellectual merits: The proposed work explores a new approach to developing integrated reconfigurable filters with wide tuning range and reduced loss. This new approach relies on the acoustoelectric effect, a phenomenon caused by interactions between electrons and phonons. Using this effect, which is most effective in nano-scale, a new class of nano-mechanical acoustic filters with potentially negative loss (i.e. positive gain) will be developed. This will yield new opportunities for acoustic devices and instrumentation. In addition, using advanced 3D micromachining techniques microscale tunable lumped components with unparalleled Qs exceeding 150 and wide tuning range will be developed. The high-Q tunable passives will be utilized to reduce parasitics of acoustic filters and assist in tuning their frequency response. The PI will leverage her prior work on high-Q passives and micro-fabrication techniques towards this proposed research. Along with the experimental work, the proposed research aims to advance the scientific community?s understanding of the physical phenomena that govern the performance of the proposed MEMS arrays and new technologies that overcome these physical limits. Broader Impact: The proposed research enables on-chip reconfigurable high-Q filtering, eliminating many of the redundant components in RF transceivers, which results in drastically smaller form factor and reduced power consumption. In a cellular phone, elimination of only one off-chip fixed-frequency filter as well as the associated matching network using the proposed technique reduces the transmit printed circuit board area by more than 75%, while lowering the bill-of-materials. As such, the proposed research will have transformative impact on telecommunication. The reconfigurable MEMS filters developed in this CAREER program could have far-reaching applications beyond wireless communication ranging from medical ultrasonic imaging to non-contact sensing. In addition to the outlined research effort, an integrated educational program will be established which aims to educate students through direct participation in the research activities. The outreach efforts of this project are aimed at promoting diversity among engineers and scientists and specifically increasing the proportion of women in engineering to a healthy level (>30%). To reach this goal and to motivate and educate students, the PI will pursue the following avenues: (1) Educational outreach through School of Education to high school teachers to observe the classroom dynamics in the 6th and 7th grades where female students start to lose interest in engineering as well as summer outreach programs to expose high school students to the field of MEMS by involving them in the proposed research activities; (2) Involvement of undergraduate students from underrepresented groups in PI?s research and educational activities; (3) Creating a multi-disciplinary scientific learning environment for students and training several doctoral students; (4) Introduction of a new graduate course on RF MEMS. Students will gain research experience and discover real world applications of RF MEMS through team projects in a laboratory setting; (5) Dissemination of the scientific results of this research.