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

对无线电频谱的巨大需求是过去20年无线技术应用取得突破的结果。在21世纪，无线电频谱的可获得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无线电频率(RF)信号和系统，而且人们在日常生活中也依赖于电子邮件、冲浪、预订旅行、与朋友“Skype”打字、在路上远程导航、与家庭传感器和安全系统通信以及分享社交活动。随着对射频频谱的需求不断增加，各种系统和应用之间的射频干扰水平也越来越高，频谱变得越来越拥挤。与此同时，我们仍然严重依赖遥感系统来空中探索我们的星球，监测环境变化及其对我们生活的影响，以及天气预报和自然灾害预警。这些遥感系统通常试图接收和检测微弱的射频信号，容易受到故意的射频干扰，甚至包括商业通信系统在内的随机射频源。在用于遥感和商业无线通信应用的现代无线系统中，抑制不需要的RF信号正变得非常重要。如果不解决射频干扰问题，增强对现有射频频谱的访问将是不可能的，特别是在对射频系统带宽的需求快速增长和射频接收器变得更加敏感的情况下。该项目将通过开发复合磁性纳米材料来解决射频干扰问题，该纳米材料可以作为薄膜沉积在各种衬底上，并提供一种称为频率选择性限幅器(FSL)的可调射频信号抑制装置。该设备将在接近要保护的系统的工作频带的给定频率上显著衰减高于特定功率电平的任何信号。因此，根据干扰的强度，FSL充当自适应滤波器。将对材料成分和射频响应(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有一个基本的了解，以便为任何遥感或无线通信应用中的目标射频干扰抑制FSL量身定做。一个重要的目标是获得在1-20 GHz范围内具有这种性能的紧凑型和平面型射频器件，用于集成到片上系统(SoC)或封装上系统(SOP)射频前端。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)了解直流偏置磁场强度和方向的影响；以及(4)通过使用磁性纳米材料创建平面射频电路，展示1-20 GHz范围内表现出FSL响应的坚固的平面RFI抑制器件的可行性。这一主题还有助于让学生接触纳米技术和射频硬件技术，他们中的许多人今天都在使用这些技术。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.