SpecEES:Switched-Capacitor Radiofrequency Signal Processing for Spectrally-Agile Low-Energy Wireless Transceivers

在过去的几十年里，由于计算和通信的进步，信息处理和获取的持续便利性已经对社会和全球产生了最深远的影响之一。从20世纪80年代左右开始，每十年都有无线标准的重大改进（20世纪80年代的1G， 90年代的2G， 2000年代的3G和2010年代的4G），每个都需要新的基础设施和支持设备。第五代无线标准的目标是将整体无线容量提高1000倍，提高覆盖范围，减少延迟，预计将在未来十年内部署。另一方面，在物联网（IoT）的愿景下，无线连接设备的数量呈指数级增长。频谱管理、安全保障和能源效率是实现未来无线网络的关键参数。提出的研究重点是射频（RF）集成电路的设计和实验演示，这些电路可以在商业半导体制造工艺中实现，并使节能的频谱敏捷无线通信收发器成为可能。节能安全无线接入是美国国家工程院（NAE）确定的几个重大工程挑战的核心，如推进健康信息学、恢复和改善城市基础设施、增强虚拟现实和推进个性化学习。该项目将有助于培养下一代工程师，并鼓励更广泛的年轻大学预科学生考虑从事工程和技术。研究成果有望转化为产业商业化，最终转化为课程。无线收发器的能量效率在受噪声支配时由发射机（主要是功率放大器）的能量效率决定，在受干扰支配时由接收机（主要是滤波器和本振）的能量效率决定。在传统方法中，上述电路的能量效率与电路中使用的谐振器和电感器的质量因子(Q)直接相关。频谱敏捷性要求射频收发器电路在宽频率范围内可调。遗憾的是，在标准集成电路平台中不存在紧凑的高q可调谐谐振器和电感器。因此，使用传统方法会增加频谱敏捷射频收发器的功耗、尺寸和成本。最近的研究已经证明了频率敏捷的离散时间（采样），或者更一般地说，周期性时变的射频电路，如开关电容滤波器和功率放大器，不需要高q可调谐电感或谐振器。该项目侧重于离散时间、周期或准周期时变射频信号处理器的理论、设计和实验验证，重点是频谱敏捷性和能量效率。具体研究方向包括：利用嵌入式滤波开关电容功率放大器，由δ - σ混合调制器驱动的节能、频率灵活的射频发射机；多输入多输出（MIMO）离散时间射频信号处理器；线性周期或准周期时变网络分析及其在可重构射频滤波器和多路复用器中的应用；节能，紧凑的频率合成器利用基于环形振荡器的数字锁相环的相位噪声和杂散抵消技术。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.