CAREER: Non-Reciprocally-Coupled Load-Modulation Platform for Next-Generation High-Power Magnetic-Less Fully-Directional Radio Front Ends

无线频谱日益严重的拥塞和过度拥挤迫切需要新的频谱高效的通信系统架构，例如全双工和大规模多输入多输出(MMIMO)。这些新兴系统需要全定向射频(RF)前端，这通常需要笨重而昂贵的磁性设备，以实现天线接口上的信号循环/隔离的关键功能。尽管非磁性芯片承诺具有大规模可制造性的芯片级集成，但它们非常低的功率处理能力仍然是瓶颈。这个职业项目旨在通过将一种新的间接信号循环/隔离范例集成到流行的负载调制功率放大器(PA)中，从根本上释放非磁性非互易器件的高功率运行，称为非互惠耦合负载调制(NRC-LM)。更广泛地说，这种“间接”设计范例可以推广到其他功率敏感设备，例如可调谐滤波器、声波滤波器和开关，这些器件可以实现高功率频率捷变射频前端，并影响认知无线电领域。在技术前沿之外，这项研究将解决国家在频谱可持续性和高速连接无处不在的覆盖方面的核心利益，可能会带来巨大的经济效益。此外，通过使用NRC-LM提高PAS(所有无线平台上最耗能的单元)的效率，可以改善整个无线生态系统的能源效率和环境影响。这项研究的影响将通过几项教育和外联活动进一步扩大：(1)将通过新的课程单元加强中佛罗里达大学的射频/微波课程。(2)将设计多样化的辅导和外展计划，以吸引STEM中代表性不足的少数群体的学生，从而为射频行业培养一支新的多元化劳动力队伍。(3)通过一系列引人入胜的努力，促进本科生参与射频/微波研究。(4)为激发K-12学生及一般市民的兴趣，将设计一系列“揭开无线通讯神秘面纱”的迷你讲座，并在外展活动中展出，以及在社交媒体平台上传播。本课题的目标是建立基于NRC-LM的高功率无磁全定向射频前端的理论基础和实用设计方法。通过利用有源负载调制的独特特性，环行器布置从功率放大器输出的高功率节点转换为内部低功率节点，同时保持关键的信号循环/隔离行为。这种改造不仅从本质上消除了非磁性环行器承受不起的功率压力，而且大大减轻了其不可原谅的损耗和非线性对整个发射机的影响。(1)作为实际设计的基础，系统地建立了新的NRC-LM定向发射和接收理论，并将其推广到所有现有的负载调制模式。(2)此外，还将研究结合先进的多输入NRC-LM发射机结构的数字-射频混合设计，以在任意带内频率下协同非磁性环行器和有源LM之间的最佳合作，从而极大地提高带宽、效率、线性度、动态范围等。(3)同时，提出了一种新型的正交换向环行器，以提供超宽带、瓦级功率处理和低损耗。(4)此外，还将研究创新的系统级设计，将基于NRC-LM的前端集成到mMIMO(基于天线阵列)和全双工系统中，从而实现前所未有的频谱和能源效率以及多频段和多标准能力。总体而言，这项研究的成功将显著促进下一代频谱和节能通信。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The exacerbating congestion and overcrowding of wireless spectrum strongly demand new spectrally efficient communication system architectures, e.g., full duplex and massive multi-input multi-output (mMIMO). These emerging systems necessitate fully-directional radiofrequency (RF) front-ends, which normally involve bulky and expensive magnetic devices for a critical function of signal circulation/isolation at the antenna interface. Although the non-magnetic counterparts promise chip-level integration with massive manufacturability, their very low power-handling capability remains as the bottleneck. This CAREER project aims to fundamentally unleash the high-power operation of non-magnetic non-reciprocal devices though a new paradigm of indirect signal circulation/isolation integrated into the prevailing load-modulation power amplifiers (PAs), named Non-Reciprocally-Coupled Load Modulation (NRC-LM). More broadly, this ‘indirect’ design paradigm can be generalized to other power-sensitive devices, e.g., tunable filters, acoustic-wave filters, and switches, which could enable high-power frequency-agile RF front-ends and impact the field of cognitive radios. Beyond the technological frontiers, this research will address the nation’s core interests in spectrum sustainability and ubiquitous coverage of high-speed connectivity, potentially leading to immense economic benefits. Moreover, by enhancing the efficiency of PAs (the most energy-consuming unit on all wireless platforms) with NRC-LM, the energy efficiency and environmental impacts of the entire wireless ecosystem can be improved. The impact of this research will be further expanded through several educational and outreach activities: (1) The RF/microwave curricula at the University of Central Florida will be enhanced with new class modules. (2) Diverse mentoring and outreach programs will be designed to attract students of underrepresented minority groups in STEM, thus preparing a new diverse workforce for the RF industry. (3) The engagement of undergraduate students in RF/microwave research will be promoted through a comprehensive set of intriguing efforts. (4) To stimulate interests from K-12 students and general public, a series of “demystifying wireless communications” mini lectures will be designed, exhibited in outreach activities, and disseminated on social media platforms. The objective of this CAREER project is to establish the theoretical foundation and practical design methodologies for high-power magnetic-less fully-directional RF front-ends based on NRC-LM. By leveraging a unique characteristic of active load modulation, the circulator placement is transformed from the high-power node of PA output to an inner low-power node, while maintaining the critical signal circulation/isolation behavior. This transformation not only inherently eliminates the unaffordable power stress on non-magnetic circulator but also greatly mitigates the impact of its unforgiven loss and non-linearity on the overall transmitter. The proposed research comprehensively spans over theory, design practice, and system architecture: (1) As a foundation of practical designs, the new NRC-LM theory in terms of directional transmission and reception will be systematically established and generalized to all existing load-modulation modes. (2) Moreover, mixed digital-RF design in conjunction with advanced multi-input NRC-LM transmitter architecture will be investigated to synergize an optimal cooperation between non-magnetic circulator and active LM at arbitrary in-band frequencies, pushing extreme bandwidth, efficiency, linearity, dynamic range, etc. (3) Meanwhile, a novel quadrature-commutated circulator is proposed to offer ultra-wide bandwidth, watt-level power handling, and low loss. (4) Furthermore, innovative system-level designs will be studied to integrate the NRC-LM-based front-ends into mMIMO (antenna-array-based) and full-duplex systems, which can lead to unprecedented spectrum and energy efficiencies as well as multi-band and multi-standard capabilities. Overall, the success of this research will significantly enhance the next-generation spectrum- and energy-efficient communications.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.