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

在过去的20年里，随着无线技术应用的突破，对无线电频谱的巨大需求已经到来。在21世纪，获取无线电频谱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信号和系统，而且人们在日常生活中也使用无线电频率来收发电子邮件、上网、预订旅行、与朋友“skype”聊天、在路上远程导航、与家庭传感器和安全系统通信、分享社交活动。随着对射频频谱需求的不断增加，频谱变得越来越拥挤，各种系统和应用之间的射频干扰水平也越来越高。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测，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，甚至是随机的射频源，包括商业通信系统。在遥感和商业无线通信应用的现代无线系统中，减轻不需要的射频信号变得至关重要。如果不解决射频干扰问题，就不可能增强对现有射频频谱的访问，特别是因为对射频系统带宽的需求正在迅速增长，射频接收器变得越来越敏感。该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，该材料可以作为薄膜沉积在各种衬底上，并提供可调谐的射频信号抑制装置，称为频率选择限制器（FSL）。该装置将显著衰减任何信号高于特定功率水平在给定频率，这是接近系统的工作频带被保护。因此，FSL作为一个自适应滤波器依赖于干扰的强度。对材料组成和射频响应之间的相互作用和关系（抑制频率，抑制水平，抑制带宽，直流磁场偏置）的基本理解将被追求，以便在任何遥感或无线通信应用中定制FSL以拒绝目标射频干扰。一个重要的目标是在1-20 GHz范围内实现具有这种性能的紧凑平面RF器件，以便集成在片上系统（SoC）或包上系统（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电平；(3)了解直流偏置场强和方向的影响；(4)通过使用磁性纳米材料创建平面射频电路，展示了在1-20 GHz范围内具有FSL响应的鲁棒平面射频干扰抑制装置的可行性。这个主题也适合让学生们接触到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。本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外展计划。

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.