The objective of this research is the discovery, investigation, and application of low loss, high dielectric constant artificial electromagnetic materials at high frequencies. Of particular interest are materials that can be printed with low temperature methods enabling their direct integration into a wide range of electromagnetic devices. The approach is based on a comprehensive plan of theory, simulation, fabrication and measurement of these materials to prove their properties.
Intellectual Merit: The main focus of this research is on multi-scale artificial dielectric materials. Potentially transformative properties of this new class of materials for RF/microwave circuits are obtained through simultaneous incorporation of multiple dielectric enhancement effects on different length scales resulting in a very large effective dielectric constant with small loss tangent. The key attributes of these multi-scale artificial dielectrics that distinguish them from others are low loss and printability. Using these properties and their spatial tailorability, the new artificial materials will be applied to (1) planar antenna miniaturization and gain enhancement, and (2) microwave filter performance enhancement and miniaturization.
Broader Impacts: It is anticipated that this new technology will have broad engineering application with special benefit to society. Wide utilization of this technology is foreseen in industrial and academic labs that can benefit from such artificial materials but have been prevented by complexities in designing, manufacturing, and integrating these materials into their devices and subsystems. The research will include both graduate and undergraduate student participation. The research findings will be integrated into two graduate courses and parts disseminated via the internet.
The performance of high frequency electronic devices can be greatly affected by the materials from which they are constructed. Such devices may be found in products such as cellular telephones, radars, wireless routers, microwave data links, and many others. An important focus of this research project was on the creation of so-called artificial electromagnetic materials that have useful properties that cannot be found in naturally occurring materials. Further, we wished to create useful materials that have properties that we can first specify, then create them accurately in the laboratory for use in devices to enhance their performance (see attached image). Such a capability was achieved in this research. We made a number of discoveries and contributions to science and engineering based on this NSF-funded research project. For one, we created a new type of artificial electromagnetic material based on what we call a "dumbbell" particle (see attached image). This new type of electromagnetic material is able to achieve designable electromagnetic properties with very large values, without suffering from large losses (which would greatly diminish the usefulness of these artificial materials in devices). We also mathematically refined and extended a famous method for calculating these electromagnetic material properties from accurate computer simulations. One device that we found can be greatly aided by such artificial materials is an antenna called a resonant cavity antenna (RCA). The RCA is a class of high-gain antennas, i.e., it is capable of directing the beam towards a desired direction. Unlike most other classes of high-gain antennas, such as the parabolic dish, the RCA is flat and contains minimum mechanical complexity; so, it is much less expensive. Unfortunately, a big problem with such an antenna is its frequency bandwidth, which limits the rate at which data can be sent and received by such antennas. Generally, a higher gain RCA operates over a narrower frequency band. Many high-gain applications require minimum useful bandwidths that a traditional RCA doesn’t deliver. Our research provided several approaches to overcome the bandwidth problem and develop more practical RCAs. In fact, the best antenna performance was obtained with a round superstrate that is quite puck like, so, we named this practical version of the RCA the "puck antenna" (see attached image). The performance of a puck antenna that we designed and built from commercial materials was four times that of the traditional RCA and, yet, much smaller. Also, through this NSF-funded project, we were able to create hands-on learning opportunities for high-school aged students and Native American students. A "Buffalo Antennas" summer camp mini-course was created at our university to give high-school aged students an opportunity to learn about the fascinating world of electromagnetics. Two activities were created for different groups of students, and both involved hands-on laboratory experiences including antenna design and fabrication, soldering, and culminating with the students measuring their own antenna performance. The first activity involved Native American high school girls (see attached image) and was conducted as part of the SD GEAR UP program, which is a program that helps students be successful in a college setting. This program is operated in collaboration with many schools and represents all nine tribes in South Dakota: Cheyenne River, Crow Creek, Flandreau-Santee, Lower Brule, Oglala, Rosebud, Sisseton-Wahpeton Oyate, Standing Rock, and Yankton. This program boasts some very impressive statistics: of those students who graduate from these programs, virtually 100% also graduate from high school, 85% attend college, while 7% of them join the military. The second activity involved high school-aged boys (see attached image) and was conducted as part of the Students Emerging as Professionals (STEPS) program, which is a one-week camp that provides students with an introduction to the world of technology and engineering. Students participate in activities that give them hands-on experience with high tech equipment and processes, and basically to learn more what engineers do. In this student professional development program the target users are students that may attend South Dakota School of Mines and Technology in the future. Thanks to this NSF-funded project, we were able to conduct exciting research that resulted in more than six journal papers (with at least four more in preparation), and dovetail it with the education of students of all levels and backgrounds (from K-12 to PhD). Moreover, it helped support three BS level students through summer research experiences, and support several graduate students (MS and PhD level), all of which currently have careers in their fields of interest in the United States.
