Seminar: Zheng Liu

“Universal Frequency-agile and Energy Efficient Arrays and Transmitters at mmWave”
Friday, Feb. 23 at 1:00pm
MALA 5050
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The evolving spectral allocations in the mmWave bands across 30-100 GHz for 5G-beyond/6G creates unparalleled opportunities for the next generation of communication and sensing. The potential to flexibly operate across any part of these spectrums could revolutionize wireless interfaces, making a universal front-end the cornerstone for intelligent wireless network. Phased array systems, essential for modern mmWave interfaces due to their beamforming capabilities, consist of intricately co-designed and co-packaged array of antennas and transceivers. However, their operational frequency range is severely limited by 1. spatial aliasing in antenna arrays and 2. the challenge of developing broadband transmit/receive circuits (especially power amplifies). This limitation highlights the need for innovation towards truly universal and frequency-agile phased array front-ends.

In this seminar, I will present a holistic approach to addressing the challenges of developing a universal mmWave array interface and its constituent circuits, enabling efficient operation across an ultra-wideband frequency range of 30-100GHz. To this end, I will firstly introduce the insights and optimization strategies toward nature inspired aperiodic sparse antenna array geometries, which are capable of operating across ultra-wide frequency ranges while overcoming the trade-offs among directivity, inter-element coupling, and grating lobe issues. The proof of concept design and measurement results will be discussed. Secondly, I will present multidimensional (device, architecture, and methodology) techniques for mmWave broadband and high-efficiency power amplifiers in various IC technologies. Innovative ideas include stacked common base PA cells, non-Foster impedance synthesis for high back-off efficiency over wide frequency range, and deep learning-enabled PA inverse design methodology. Building on the innovations from the previous two sectors, I will finally present, for the first time, the design of an ultra-wideband, frequency-agile transmitting phased array system. It features an 8-channel, 30-100GHz fully integrated phased array IC and a multi-chip large-scale 120-element system with 3D packaging. We will explore key ultra-wideband novel designs, including phase shifters and on-chip passives. This research marks a significant step toward frequency-agile phased-array systems that operate across various mmWave standards. By extending universality, enhancing security, and reducing costs, this work aims to redefine the future landscape of wireless communication and sensing platforms.


Dr. Zheng Liu earned his B.S. degree in Electronics from Peking University, China, and obtained his Ph.D. degree in ECE from Princeton University in 2023. During his doctoral studies, Zheng interned at Apple Inc., focusing on mmWave silicon transceiver design. From 2015 to 2018, he was a senior design engineer at Skyworks Solutions Inc., where he developed GaAs RF front-ends for mobile applications. He is currently with Texas Instruments, Inc. Zheng’s research interests include mmWave/sub-THz power amplifiers, broadband transceiver architectures, and intelligent phased array systems for next generation wireless communication and sensing applications. Dr. Liu is the recipient of the Bede Liu Best Ph.D. Dissertation Award from Princeton University ECE in 2023, the Advanced Practice Paper Award from IEEE International Microwave Symposium (IMS) in 2022, the IEEE MTT-s Graduate Fellowship in 2021, and three IEEE IMS Best Student Paper Awards. He serves as an affiliate member of the IEEE MTT-S Technical Committee on Microwave and Millimeter-Wave Integrated Circuits.