We focus on developing analog/RF/mmWave integrated circuits and micro-systems for wireless communications, sensing, and biomedical applications. In such applications, energy efficiency, bandwidth, size, and security are critically important performance metrics. Our research goals are to push the fundamental limitations in these aspects and, at the same time, enable exciting new applications through innovations in application-specific integrated circuits (ASIC) design, advanced electromagnetics, and their tight integration. Specifically, we focus on conducting theoretical analysis of circuit problems, developing new hardware capabilities, and performing system-level engineering. A few recent and ongoing research efforts are highlighted below.
mmWave / sub-THz Transceivers for 5G and Beyond
One of the biggest moves for 5G communications is shifting up the carrier frequency to mmWave, leading to a 10× increase in the data throughput. With the ongoing 5G deployment, an outlook to the future is to further increase the frequency – FCC recently opened up a few bands above 95 GHz for unlicensed use to encourage the development of 6G. To truly harness mmWave/sub-THz bands in large-area networks, we need to satisfy three system requirements simultaneously – wide network coverage, high bandwidth, and support for high user mobility. Towards this end, we are particularly interested in energy-efficient, wideband, and reconfigurable transceiver building blocks, antennas, and beamforming systems.
Related Publications: RFIC 2022 & JSSC 2023 (three-way Doherty PA), CICC 2021 (hybrid beamforming), MWCL 2021 & T-CAS I 2023 (broadband LNA for multi-band 5G), ISSCC 2017 (100-300GHz broadband TRX).
Conventionally, antennas and electronics are often treated as two distinct and separate domains: antenna designers handle the antennas; circuit designers deal with the electronics; and they only talk to each other over one single standard 50Ω interface. However, this partitioned approach may not lead to a globally optimal design if we artificially impose a boundary between antennas and electronics. It is noteworthy that the far-field antenna radiation characteristics are completely governed by its local current or voltage distributions, suggesting the possibility of actively synthesizing the desired antenna responses using multiple electronic feeds. Multi-feed antennas co-integrated with complex electronics now emerge as a very promising technology particularly for wireless communication and radar systems.
On-chip or on-package multi-feed antennas can support low-loss on-antenna power combining in one single antenna footprint, radically pushing the limit of output power and efficiency for wireless transmitters. The multi-feed antennas also enable on-antenna active load modulation, achieving high-efficiency on-antenna Doherty or Outphasing architectures with state-of-the-art energy efficiency. Furthermore, inherently wideband feed isolation can be explored in multi-feed antennas to realize millimeter-wave polarization-division-duplex wireless links with multi-Gbit/s complex modulated signals.
Related Publications: JSSC 2019, JSSC 2018, ISSCC 2018, RFIC 2018 (Best Student Paper Award 2nd place), ISSCC 2017, T-AP 2017.
A major technological need to further advance brain science is to develop neural interfaces that can record and stimulate neural activity across a large number of neurons and across all relevant time scales. Emerging brain-machine interfaces built on large-scale neural recording can decipher brain activities; the decoded information can then be used to control neural prosthetics to restore lost sensory or motor functions for paralyzed patients. On the neural stimulation side, deep brain stimulation (DBS) has proven to be highly effective in treating brain disorders (such as Parkinson’s disease) by injecting a pulsed current with a pre-defined pattern. In collaboration with Rice Neuro-engineering Initiative and Texas Medical Center, we are particularly interested in developing new methodologies and hardware interfaces for neural recording and stimulation.
Related Publications: T-BioCAS 2021, ISSCC 2021, T-BioCAS 2015, ISSCC 2015, VLSI 2016.