Speaker: Ting Lu
Affiliation: Ph.D. Candidate
Via Zoom: https://ucla.zoom.us/j/91010507369?pwd=SDIwQWhMN1BkM3R2WTdFU3NLamhwdz09
Abstract: As the communication technology develops, the complexity of mobile RF front ends increases as a result of advanced communication standards. This requires next generation RF front-end to be more efficient and compact than presently available. Acoustic wave devices have been widely used for filters and duplexers due to their excellent quality factor and small footprints at radio frequency. Acoustic duplexers offer great isolation for transmitting and receiving signals at closely spaced frequency bands in frequency division duplex communication systems. However, the exploitation of these acoustic wave technologies remains in the passive domain rather than active domain. To overcome these challenges, our work explores parametric mixing and amplification on the acoustic wave platform, with the aim to develop a new class of nonlinear acoustic components such as enhanced acoustic filters and mixers.
Firstly, we propose acoustic nonlinear transmission line concept using the analogy between electromagnetic wave and acoustic wave, i.e., parametric mixing is expected to happen in the nonlinear acoustic waveguide where the mechanical stiffness is modulated by the pump wave. This concept is proven using multi-physics finite element simulation and validated with analytical equations. Secondly, practical implementations of acoustic nonlinear transmission line using nonlinear materials including Barium Strontium Titanite (BST) and Aluminum Nitride (AlN) are investigated. An acoustic nonlinear transmission line circuit model is developed to simulate the parametric effects more efficiently than finite element simulation. Parametric mixing and frequency conversion are observed in the BST coupled surface acoustic wave grating and in the AlN Lamb wave delay line. Moreover, a non-degenerate phase independent parametric Q-enhancement technique is explored and demonstrated on the AlN Lamb wave resonator. This technique is implemented by parametrically pumping AlN material stiffness to realize a negative resistance seen at the signal path. A multi-resonance coupled nonlinear model is developed to simulate the parametric coupling of each resonance and extract the nonlinearity of AlN from experimental data. The device quality factor is boosted in both simulation and experiment with proper pump frequency and pump power. To summarize, this work presents a complete study of parametric mixing and amplification on the nonlinear acoustic platform, and it can be readily capitalized to develop nonlinear acoustic devices for future communication systems.
Biography: Ting Lu received the B.S. degree in Information Engineering (Optics) from Zhejiang University, China in 2016, and the M.S. degree in Electrical and Computer Engineering from UCLA in 2018. She is the recipient of UCLA Dissertation Year Fellowship in 2020, and UCLA ECE Department Fellowship in 2016. She interned at Qualcomm Technologies, Inc. for wireless product development in 2019, and interned at Skyworks Solutions, Inc. for RF front-end filter design and module optimization in 2018. Her research includes nonlinear acoustics, time-varying electromagnetics, and wireless communication.
For more information, contact Prof. Yuanxun Ethan Wang ()
Date(s) - Apr 26, 2021
9:30 am - 11:30 am
Via Zoom Only
No location, Los Angeles