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，这对射频硬件提出了更严格的限制。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的电调谐射频前端类别，用于在频谱拥塞环境中实现高效的按需频谱访问/共享。虽然5G网络、设备和通信方案已经得到了广泛的讨论，但它们还没有得到适当的定义、部署和充分利用。该项目的目标是开发具有多级别传递函数自适应能力的射频前端，该前端由电控材料和新型射频滤波器实现，可以：(A)任意定义工作频段；(B)在动态频谱分配下高效发送/接收；以及(C)在未授权频段中共存。与其他收发组件(如天线、功率放大器和低噪声放大器)的联合设计将提高功率效率，同时减小射频前端的尺寸。多层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。这项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，他们在射频过滤器、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)通过国家科学基金会本科生研究经验(REU)计划以及大学和行业资助的学生机会，扩大本科生在实践培训和研究方面的经验；(Ii)加强UCB/UM课程，增加新的课程内容，整合拟议的研究成果；(Iii)通过组织活动和大学奖学金计划积极招募本科生/研究生，增加未被充分代表的本科生/研究生的参与；以及(Iv)通过UCB/UM现有的基础设施，如加州大学伯克利分校完善的科学发现计划，为K-12学生开展外展工作。拟议合作研究的技术目标是调查新的完全可重新配置的共同设计的射频前端，这些前端将有助于在频谱最拥堵的6 GHz以下的频率下高效接入频谱。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。拟议的硬件开发将利用钛酸锶(BST)作为体声波谐振器(FBAR)和电调谐无功元件的结构材料的多功能压控特性。这可以通过以下方式显著增加功能：(1)用于连续和模拟RF调谐的新的滤波器设计方法和调谐方案；(2)具有内在开关传递函数的高品质因数FBAR；(3)共同设计的RF无源和有源电路元件，从而实现小型化和降低损耗；以及(4)频率选择性灵活的谐波终端，以提高电路效率，并动态适应具有不同频谱和空间内容的RF信号。这项合作研究工作将导致开发具有多级传递函数自适应能力的无开关发射器/接收器前端链，能够实现比传统方法更高的效率和更低的噪声。建议的调谐速度在数百ns量级，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.