Over the past few decades, enabled by the advancements in computation and communication, the continued ease of information processing and access has had one of the most profound societal and global impacts. Starting around 1980s, every decade has seen a major improvement in wireless standards (1G in 1980s, 2G in 1990s, 3G in 2000s, and 4G in 2010s) each necessitating new infrastructure and supporting devices. The fifth-generation of wireless standards with the goals of improving the overall wireless capacity by 1000 times, improving the coverage, and reducing the latency is envisioned to be deployed within the next decade. On the other hand, the number of wirelessly connected devices is increasing exponentially under the internet of things (IoT) vision. Spectrum management, security assurance, and energy efficiency are key parameters to realize future wireless networks. The proposed research is focused on the design and experimental demonstrations of radio-frequency (RF) integrated circuits that can be realized in commercial semiconductor fabrication processes and enable energy-efficient spectrum-agile wireless communication transceivers. Energy-efficient secure wireless access is at the core of several Grand Challenges for Engineering that have been identified by the National Academy of Engineering (NAE) such as Advance Health Informatics, Restore and Improve Urban Infrastructure, Enhance Virtual Reality, and Advance Personalized Learning. This project will enable training the next-generation engineers and encouraging broader participation of young pre-college students to consider pursuing engineering and technology. The research results are expected to be transitioned to industry for commercialization and ultimately transform the curriculum.

The energy efficiency of wireless transceivers, when dominated by noise, is dictated by the energy efficiency of transmitter (mainly power amplifier) and, when dominated by interferences, is dictated by the energy efficiency of receiver (mainly filters and local oscillator). In the conventional approach, the energy efficiency of the above circuits is directly related to the quality factor (Q) of the resonators and inductors used in the circuit. Spectrum agility requires RF transceiver circuits to be tunable across a wide frequency range. Unfortunately, compact high-Q tunable resonators and inductors do not exist in standard integrated circuit platforms. Consequently, the power consumption, size, and cost of a spectrum-agile RF transceiver would be increased by using the conventional approach. Recent research has demonstrated frequency-agile discrete-time (sampled), or more generally, periodic time varying, RF circuits, such as switched-capacitor filters and power amplifiers, that do not require high-Q tunable inductors or resonators. This project focuses on theory, design, and experimental verifications of discrete-time, periodic or quasi-periodic time varying RF signal processors with emphasis on spectrum agility and energy efficiency. Specific research directions include the following: energy-efficient and frequency-agile RF transmitters leveraging switched-capacitor power amplifiers with embedded filtering and driven by hybrid delta-sigma modulator; multi-input multi-output (MIMO) discrete-time RF signal processors; linear periodic or quasi-periodic time-varying network analysis with applications in reconfigurable RF filters and multiplexers; and energy-efficient, compact frequency synthesizers leveraging phase-noise and spur cancellation techniques in ring oscillator-based digital phase locked loops.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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University of Southern California
Los Angeles
United States
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