SpecEES:Collaborative Research: Power and Spectral Efficiency enabled by RF Co-Designed Electrically-Adaptive Front Ends

无线通信和传感的快速发展要求更有效地利用宝贵的频谱，对射频硬件施加了更严格的限制。为了应对这一挑战，需要变革性的无线电前端设计。该合作项目提出了新型的电调谐射频前端，以在频谱拥挤的环境中实现高效、按需的频谱接入/共享。尽管5G网络、设备和通信方案已经被广泛讨论，但它们尚未得到适当的定义、部署和充分利用。该项目的目标是开发具有多级传递函数自适应的射频前端，该前端由电控材料和新型射频滤波器实现，可以：(a)任意定义操作频带；(b)在动态频谱分配下有效地发送/接收；和(c)共存于未授权频段。滤波器与其他收发器组件（如天线、功率放大器和低噪声放大器）的协同设计将提高功率效率，同时减小射频前端的尺寸。多层次自适应和电路协同设计是基本的方法进步，将允许硬件性能的变革性改进。拟议的研究将由科罗拉多大学博尔德分校（UCB）和密歇根大学（UM）的一个独特的多研究所团队进行，他们在射频滤波器、有源电路和微制造方面具有互补的专业知识。该项目的外展部分侧重于：(i)通过美国国家科学基金会本科生研究经验（REU）计划扩大本科生在实践培训和研究方面的经验，以及为学生提供大学和行业资助的机会；（ii）以整合建议研究成果的新课程内容，加强UCB/UM的课程设置；（iii）通过有组织的活动和大学奖学金项目积极招募，增加代表性不足的本科生/研究生的参与；（iv）通过UCB/UM现有的基础设施，如UCB完善的科学发现计划，为K-12学生提供外展服务。拟议的合作研究的技术目标是研究新型的完全可重构的共同设计的射频前端，以促进在频谱最拥挤的6 GHz以下频率下的有效频谱接入。对于5G应用，毫米波频率分配允许更大的带宽，但伴随着更高的大气损耗和更高的成本。提出的硬件开发将利用钛酸钡锶（BST）的多功能电压控制特性作为体声波谐振器（fbar）和电调谐反应元件的结构材料。这允许通过以下方式显著增加功能：(1)用于连续和模拟RF调谐的新滤波器设计方法和调谐方案；(2)具有本质开关传递函数的高品质因数fbar；(3)共同设计射频无源和有源电路元件，实现小型化和降低损耗；(4)频率选择敏捷谐波终端，提高电路效率，动态适应不同频谱和空间含量的射频信号。合作研究成果将导致无开关的发射器/接收器前端链的发展，具有多层传递函数自适应能力，能够实现比传统方法更高的效率和更低的噪声。所提出的数百ns的调谐速度将允许0.8 - 6 GHz的动态频率覆盖和自适应多频带前端链。

The rapid growth of wireless communications and sensing demand more efficient use of the precious frequency spectrum, imposing tougher constraints on the radio-frequency hardware. To responds to this challenge, transformative radio front-end designs are needed. This collaborative project proposes new classes of electrically-tuned RF front-ends for efficient, on-demand spectrum access/sharing in spectrally-congested environments. Although 5G networks, devices and communication schemes have been extensively discussed, they are not yet appropriately defined, deployed and fully exploited. The goal of this project is to develop RF front-ends with multiple levels of transfer-function adaptivity enabled by electrically-controlled materials and new types of RF filters that can: (a) arbitrarily define the band of operation; (b) efficiently transmit/receive under dynamic spectrum allocations; and (c) co-exist in unlicensed bands. The co-design of filters with other transceiver components such as antennas, power amplifiers and low-noise amplifiers will increase power efficiency while reducing the size of RF front-end. The multi-level adaptivity and circuit co-design are fundamental methodology advances which will allow transformative improvements in hardware performance. The proposed research will be carried out by a unique multi-institute team from the University of Colorado at Boulder (UCB) and the University of Michigan (UM), with complementary expertise in RF filters, active circuits and microfabrication. The outreach components of this project focus on: (i) broadening the undergraduate experience in practical training and research through NSF Research Experiences for Undergraduates (REU) program, as well as university and industry-funded opportunities for students; (ii) enhancing the UCB/UM curriculum with new class contents integrating the proposed research results; (iii) increasing the participation of underrepresented undergraduate/graduate students by active recruiting through organized events and university scholarship programs; and (iv) outreach efforts for K-12 students through existing infrastructure at UCB/UM such as the well-established Science Discovery Program at UCB.The technical objective of the proposed collaborative research is to investigate new classes of fully-reconfigurable co-designed RF front-ends that will facilitate efficient spectrum access at frequencies below 6 GHz, where the spectrum is most congested. For 5G applications, the millimeter-wave frequency allocations allow for larger bandwidths, but are accompanied by higher atmospheric loss and higher cost. The proposed hardware developments will exploit the multi-functional voltage-controlled properties of barium strontium titanate (BST) as structural materials for bulk acoustic-wave resonators (FBARs) and electrically-tuned reactive elements. This allows for significantly increased functionality through: (1) new filter design methodologies and tuning schemes for continuous and analog RF tuning; (2) high quality factor FBARs with intrinsically-switched transfer function; (3) co-designed RF passive and active circuit elements resulting in miniaturization and reduced loss; and (4) frequency-selective agile harmonic terminations to increase the circuit efficiency and dynamically adapt to RF signals with diverse spectral and spatial content. The collaborative research effort will lead to the development of switchless transmitter/receiver front-end chains with multiple levels of transfer function adaptivity capable of achieving higher efficiency and lower noise than conventional approaches. The proposed tuning speeds on the order of hundreds of ns will allow dynamic frequency coverage in 0.8 - 6 GHz and adaptive multi-band front-end chains.