SWIFT: Interference Mitigation using Spatial and Frequency Nulling for Wideband mm-Wave Transceivers

目前部署的第五代(5G)解决方案在频段运行，大部分在6 GHz以下，在28/39 GHz有限度地运行，正在考虑扩展到其他新兴频段。当工作在28 GHz或39 GHz时，需要数百个天线来提高发射信号的功率，以形成聚焦的波束，以增加通信范围。在接收器上，有一个独特的机会，可以利用许多天线元件来抵消或减弱来自不想要的方向的干扰。该建议旨在了解实现干扰消除的最省电和最优的方法。此外，随着高速应用开始从低于6 GHz的频段过渡到更高的频率，特别是在28/39 GHz，使用高质量声学谐振器消除在其他频段(其他“通道”)运行的有害干扰的传统方法似乎不可行。因此，该项目将探索电子可调滤波器的应用，并利用现代数字设备的开关特性作为克服这些限制的一种手段。虽然解决共存问题是商业无线电的一大障碍，但如果不采取措施解决干扰问题，许多其他无线电也有失去功能和灵敏度的危险。如果干扰水平如预期的那样增加，许多重要的传感器，如天气雷达和射电天文望远镜，可能会停止工作。因此，必须通过与射电天文学团体直接合作来保护这种无线电。这项研究还将对学生进行现代通信系统和无线通信工程方面的培训。下一代无线电利用更宽频带的毫米波(毫米波)前端、更高的通道带宽(1 GHz或更高)和波束成形。多天线阵列信号处理技术自然地提供对不想要的信号的一些空间滤波。通过在天线方向图中有目的地将干扰置零，可以提高信噪比，实现更好的频谱利用率，并实现更健壮的无线电。虽然所有这些优点都可以通过数字信号处理来实现，但对模数转换器的大动态范围的要求使得百元阵列无线电功率很高，甚至不可行。此外，当毫米波频谱更加拥挤时，带外干扰可能会带来问题。使用基于高Q谐振器的锐化滤波器消除干扰的传统方法在10 GHz以上是不可行的。为了解决这些问题，将在接收器的几个位置探索干扰消除，在射频本身(使用可调电子陷波滤波器)，在射频块和模拟块之间的边界(空间陷波)，以及在模数转换器本身内部。这样，在量化之前(或量化过程中)就可以抑制干扰，这将大大降低接收机对动态范围的要求。这在5G和下一代无线电中建议的更宽的信道带宽中尤为重要。然而，干扰的消除需要知道干扰信号的位置和频率。将探索数字和基带跟踪环路以识别干扰信号的属性，然后反馈环路将允许以各种形式执行干扰消除。将研究这些无源无线电传感器保护技术的应用，如射电天文望远镜，并将调查来自射电天文学社区的干扰跟踪技术。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。

Currently deployed fifth generation (5G) solutions operate in frequency bands, mostly below 6 GHz, and to a limited extent at 28/39 GHz, and expansion to other emerging frequency bands is under consideration. When operating at 28 GHz or 39 GHz, hundreds of antennas are needed to boost the power of the transmitted signal to form a focused beam to increase the communication range. On the receiver, there is a unique opportunity to take advantage of the many antenna elements to also cancel out or attenuate interference from unwanted directions. This proposal seeks to understand the most power efficient and optimal means of achieving interference cancellation. Furthermore, as the transition of high-speed applications starts to occur from sub-6 GHz frequency bands to higher frequencies, especially at 28/39 GHz, traditional means of cancelling unwanted interference operating in other frequency bands (other “channels”) using high quality acoustic resonators does not seem viable. As such, this project will explore the application of filters that are electronically tunable and take advantage of the switching properties of modern digital devices as a means of overcoming these limitations. While addressing the coexistence issue is a major hurdle for commercial radios, many other radios are also in danger of losing functionality and sensitivity if steps are not taken to address the problem of interference. Many important sensors, such as weather radars and radio astronomy telescopes, may cease to function if interference levels increase as expected. It is therefore imperative to protect such radios by directly collaborating with the radio astronomy community. This research will also lead to the training of students in the engineering of modern communications systems and wireless communications. Future generation of radios utilize broader band millimeter-wave (mm-wave) front-ends, higher channel bandwidths (1 GHz or more), and beamforming. Multi antenna array signal processing techniques naturally provide some spatial filtering of unwanted signals. By placing nulls in the antenna pattern to purposefully “zero-out” interference, one can improve signal-to-distortion ratio, achieve better spectrum utilization, and realize more robust radios. While all these benefits can be realized using digital signal processing, the wide dynamic range requirements on the analog-to-digital converter make the hundred element array radio high power and even unfeasible. Furthermore, out-of-band interference will likely pose an issue when the mm-wave spectrum is more crowded. Traditional ways of removing interference using sharp filters based on high-Q resonators is not viable above 10 GHz. To address these issues, interference cancellation will be explored in several locations in the receiver, at the radio frequency itself (using tunable electronic notch filters), at the boundary between radio frequency blocks and analog blocks (spatial notch), as well as inside the analog-to-digital converter itself. In this way, interference will be rejected before (or during) quantization, which will reduce the dynamic range requirements of the receiver greatly. This is especially important at wider channel bandwidths proposed in 5G and future generation radios. Cancellation of interference, though, requires knowledge of the location and frequency of the interfering signal. Digital and baseband tracking loops will be explored to identify the properties of the interfering signal and feedback loops will then allow interference cancellation to be performed in the various forms. Application of these techniques for the protection of passive radio sensors, such as radio astronomy telescopes, will be studied and techniques for interference tracking from the radio astronomy community will be investigated.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.