CAREER: Analog-Assisted Transceivers for Next-Generation Millimeter-Wave Systems

由于需要更多的无线电频谱接入，商业和国家安全系统越来越多地转向毫米波载波频率。除了减小物理尺寸和重量之外，这种频率缩放也是有益的，因为它能够实现更高带宽的信号，从而产生更高的数据速率。然而，在系统级，频率缩放是有问题的，因为在大多数无线电系统中使用数字信号处理元件来生成信号并对信号进行操作。随着信号带宽的增加，数字信号处理所需的时钟速率也会增加，从而导致更多的功耗和性能下降。因此，要成功扩展到毫米波频率，就需要具有宽带信号处理替代解决方案的新型无线电架构。为了解决这个问题，该项目研究了在毫米波电路域中运行的线性和非线性模拟技术，以大幅改善下一代无线系统的信号处理。由此产生的模拟辅助架构将满足高性能无线系统至关重要的领域的需求，例如通信、物联网、自动驾驶汽车和医疗保健应用。这些技术将被纳入主要研究者的教育目标，作为侧重于无线电实验的模块，主题从系统到组件级别。首席研究员将与科罗拉多大学博尔德分校的预科和工程预科项目合作，以吸引代表性不足的第一代大学生参与工程。本研究的目标是系统地研究模拟信号处理和经典控制技术在宽带毫米波（mm波）系统中的应用，该系统采用宽带隙器件技术。缩放的基本原理表明，模拟技术在毫米波系统中变得越来越有吸引力，这是由于即使在瞬时带宽急剧增加时，在高载波频率处的分数带宽也相对较低。因此，模拟电路设计和经典控制理论的技术将被用作补偿数字域带宽限制的一种方式。提出了一种架构研究，以分析数字/射频（RF）域边界的功耗，复杂性和规模的影响时，带宽和功率是主要资源。一个具体的重点将是负载调制功率放大器的非线性分析作为一个有针对性的驱动程序，这种数字/ RF接口设计的效率提高发射机。反过来，实现模拟辅助架构将需要元件级的新型支持电路。为此，该研究将利用GaN技术开发模拟和混合模式电路，利用其高的重复频率和过渡频率。所提出的技术包括集成低频控制路径，例如，基于偏置的增益校正，以及开发用于信号生成和控制的基本构建模块。为了验证在这项工作中开发的设计方法，这些技术的演示将是一种新型的宽带收发器内置线性校正。通过该研究项目，线性和高效宽带毫米波系统的性能将得到大幅改善，从而实现电磁频谱的新的和创新的用途。该奖项反映了NSF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。

Driven by the need for increased radio spectral access, commercial and national security systems are increasingly moving to millimeter-wave carrier frequencies. In addition to reducing physical size and weight, this frequency scaling is beneficial because it enables higher-bandwidth signals which, in turn, produce higher data rates. At the system level, however, frequency scaling is problematic because of the digital signal processing elements used in the majority of radio systems to generate and operate on signals. As the signal bandwidth is increased, the clock rate required for digital signal processing is also increased, leading to more power consumption and performance degradation. Successfully expanding to millimeter-wave frequencies therefore requires novel radio architectures with alternative solutions for broadband signal processing. To address this issue, the project investigates both linear and nonlinear analog techniques, operating in the millimeter-wave circuit domain, to substantially improve the signal processing of next-generation wireless systems. The resulting analog-assisted architectures will address the needs in areas where high-performance wireless systems are critical, such as communications, internet of things, autonomous vehicles, and healthcare applications. These technologies will be incorporated into the principal investigator's educational goals as modules with focus on experimentation with radios, with topics ranging from system to component level. The principal investigator will partner with established pre-collegiate and pre-engineering programs at the University of Colorado Boulder as a way to engage underrepresented and first-generation college students in engineering.The goal of this research is to systematically investigate the application of analog signal processing and classical control techniques to wideband millimeter-wave (mm-wave) systems employing wide-bandgap device technologies. Fundamental principles of scaling indicate that analog techniques become increasingly attractive in mm-wave systems due to the relatively low fractional bandwidths at high carrier frequencies even when instantaneous bandwidths increase dramatically. Techniques from analog circuit design and classical control theory will therefore be leveraged as a way to compensate for digital-domain bandwidth limitations. An architecture study is proposed to analyze the impact of the digital / radio-frequency (RF) domain boundary on power consumption, complexity, and size when bandwidth and power are prime resources. A specific focus will be the nonlinear analysis of load-modulated power amplifiers as a targeted driver of this digital / RF interface design in efficiency-enhanced transmitters. Realizing analog-assisted architectures will, in turn, require novel supporting circuits at the component level. To this end, the research will develop analog and mixed-mode circuits in GaN technology, leveraging its high transconductance and transition frequency. Proposed techniques include integrated low-frequency control paths for, e.g., bias-based gain correction, and developing fundamental building blocks for signal generation and control. To validate the design methodologies developed in this work, the demonstration of these technologies will be a novel wideband transceiver with built-in linearity correction. Through this research project, the performance of linear and efficient wideband mm-wave systems will be substantially improved, enabling new and innovative uses of the electromagnetic spectrum.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.