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

无线频谱的日益拥挤和拥挤，强烈要求新的频谱高效通信系统架构，如全双工和大规模多输入多输出（mMIMO）。这些新兴的系统需要全方向射频（RF）前端，这通常涉及笨重和昂贵的磁性设备，用于天线接口的信号循环/隔离的关键功能。尽管非磁性的同类产品有望实现芯片级集成和大规模可制造性，但它们非常低的功率处理能力仍然是瓶颈。该CAREER项目旨在通过将间接信号循环/隔离的新范例集成到主流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，称为非往复式耦合负载调制（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，它们可以实现高功率频率敏捷RF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无处不在的高速连接覆盖方面的核心利益，可能带来巨大的经济效益。此外，通过使用NRC-LM提高pa（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推广活动进一步扩大：(1)中佛罗里达大学的射频/微波课程将通过新的课程模块得到加强。(2)将设计多样化的指导和外展计划，以吸引STEM中代表性不足的少数群体的学生，从而为RF行业准备新的多元化劳动力。(3)通过一系列有趣的努力，将促进本科生参与射频/微波研究。(4)为了激发K-12学生和公众的兴趣，我们将设计一系列“去神秘化无线通信”的迷你讲座，在外展活动中展示，并在社交媒体平台上传播。本CAREER项目的目标是建立基于NRC-LM的大功率无磁全向射频前端的理论基础和实际设计方法。通过利用有源负载调制的独特特性，环行器放置从PA输出的高功率节点转换到内部低功率节点，同时保持关键信号循环/隔离行为。这种转变不仅从本质上消除了非磁性环行器难以承受的功率压力，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。本研究将全面跨越理论、设计实践和系统架构三个方面：(1)作为实际设计的基础，系统建立新的定向发射和接收NRC-LM理论，并将其推广到现有的所有负载调制模式。(2)此外，结合先进的多输入NRC-LM发射机架构，将研究混合数字射频设计，以在任意带内频率下实现无磁环行器和有源LM之间的最佳协同，从而实现极高的带宽、效率、线性度和动态范围等。(3)同时，提出了一种新型正交整流环行器，提供超宽带宽、瓦特级功率处理和低损耗。(4)此外，将研究创新的系统级设计，将基于nrc - lm的前端集成到mMIMO（基于天线阵列的）和全双工系统中，这可以带来前所未有的频谱和能源效率，以及多频段和多标准功能。总的来说，这项研究的成功将显著增强下一代频谱和节能通信。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。

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.