EARS: Development of tunable frequency selective limiters based on novel magnetic nanomaterials for RFI mitigation in a crowded spectrum environment

过去20年来，无线电技术的应用取得了突破性的进展，对无线电频谱的需求巨大。在21世纪，无线电频谱的可访问性已成为商业和科学应用的必要条件。这是人类历史上第一次，不仅专业人士依赖于射频（RF）信号和系统，而且人们在日常生活中也依赖于访问电子邮件、上网、进行旅行预订、“Skype”他们的朋友、在路上进行远程导航、与家庭传感器和安全系统通信以及分享社交活动。随着对RF频谱的需求不断增加，频谱变得越来越拥挤，各种系统和应用之间的RF干扰水平增加。与此同时，我们仍然严重依赖遥感系统对我们的星球进行空中探索，监测环境变化及其对我们生活的影响，以及天气预测和自然灾害预警。这些遥感系统通常试图接收和检测微弱的RF信号，容易受到故意的RF干扰，甚至是随机的RF源，包括商业通信系统。 在用于遥感和商业无线通信应用的现代无线系统中，对不想要的RF信号的缓解正变得极其重要。如果不解决射频干扰问题，就不可能加强对现有射频频谱的访问，特别是由于对射频系统带宽的需求迅速增长，射频接收器变得更加敏感。本项目将通过专注于开发复合磁性纳米材料来解决射频干扰问题，该复合磁性纳米材料可以作为薄膜沉积在各种基底上，并提供可调谐的射频信号抑制频率选择限制器（FSL）。 该装置将显著衰减在给定频率处高于特定功率电平的任何信号，该频率接近于要保护的系统的工作频带。因此，FSL根据干扰的强度充当自适应滤波器。将追求对材料成分和RF响应（抑制频率，抑制水平，抑制带宽，直流磁场偏置）之间的相互作用和关系的基本理解，以定制FSL，以抑制任何遥感或无线通信应用中的目标RF干扰。一个重要的目标是实现在1-20 GHz范围内具有这种性能的紧凑和平面RF器件，用于集成在片上系统（SoC）或系统级封装（SoP）RF前端中。为此，将追求以下目标：（1）了解如何控制纳米磁性材料的铁磁共振（FMR）;（2）了解如何控制抑制带宽和阈值功率水平;（3）了解DC偏置场强度和方向的影响;以及（4）通过用磁性纳米材料创建平面RF电路来证明稳健的平面RFI抑制器件的可行性，所述平面RF电路在1-20 GHz范围内表现出FSL的响应。本主题还有助于让学生接触到他们中的许多人今天使用的纳米技术和RF硬件技术。该项目将招募来自代表性不足群体的本科生参加各种研究培训和推广计划。

The tremendous demand on the radio spectrum has come as the consequence of breakthroughs in the applications of wireless technology over the past 20 years. Accessibility to the radio spectrum has become a necessity in the 21st century for commercial as well as for scientific applications. It is the first time in the history of humankind that not only professionals depend on radio frequency (RF) signals and systems, but also people in their daily lives for accessing emails, surfing the web, making travel reservations, "skyping" their friends, tele-navigating while on the road, communicating with home sensors and security systems, and sharing social events. With ever increasing demand for the RF spectrum, the spectrum is becoming more and more crowded with increased level of RF interference among the various systems and applications. Concurrently, we still depend heavily on remote sensing systems for aerially exploring our planet, monitoring environmental changes and their impact on our lives, as well as weather prediction and early warning of natural disasters. These remote sensing systems, which typically try to receive and detect weak RF signals, are vulnerable to deliberate RF interference or even random RF sources including commercial communication systems. Mitigation of unwanted RF signals is becoming of utmost importance in modern wireless systems for both remote sensing and commercial wireless communication applications. Enhancing access to the existing RF spectrum will not be possible without addressing the RF interference issue, especially since demand on the bandwidth of RF systems is growing rapidly and RF receivers are becoming more sensitive.This project will address the RF interference issue by focusing on the development of composite magnetic nanomaterials that can be deposited as thin films on a variety of substrates and provide a tunable RF signal rejection device called a Frequency Selective Limiter (FSL). This device will significantly attenuate any signal above a specific power level at a given frequency which is close to the operational band of the system to be protected. Thus, the FSL acts as a self-adapting filter depending on the strength of the interference. A fundamental understanding on the interaction and relationship between material composition and RF response (rejection frequency, rejection level, rejection bandwidth, DC magnetic field bias) will be pursued in order to tailor the FSL for rejecting a targeted RF interference in any remote sensing or wireless communication application. An important objective is to achieve compact and planar RF devices with such performance in the 1-20 GHz range for integration in System-on-Chip (SoC) or System-on-Package (SoP) RF front ends. To do so, the following objectives will be pursued: (1) understand how to control the Ferromagnetic Resonance (FMR) of the nanomagnetic materials; (2) understand how to control the rejection bandwidth and threshold power level; (3) understand the effect of the DC bias field strength and direction; and (4) demonstrate the feasibility of robust, planar RFI rejection devices by creating planar RF circuits with magnetic nanomaterials that exhibit the response of an FSL in the 1-20 GHz range. This topic also lends itself to exposing students to nanotechnology and RF hardware technology that so many of them use today. Undergraduate students from underrepresented groups will be recruited in this project to participate in various research training and outreach programs.