Dr. Arthur D. Yaghjian (Electromagnetics Research)
Robust Field-Based Antenna Quality Factor
Abstract – New field-based quality factors Q(ω) are derived for antennas with known fields produced by an input current. These Q(ω) are remarkably robust because they equal the input-impedance bandwidth quality factor QZ(ω) when the input impedance is available. Like QZ(ω), the field-based Q(ω) is independent of the choice of origin of the antenna fields and is impervious to extra lengths of transmission lines and surplus reactances. These robust field-based quality factors are used to derive new lower bounds on the quality factors (upper bounds on the bandwidths) of spherical-mode antennas that improve upon the previous Chu/(Collin-Rothschild) lower bounds for spherical modes.
Bio – Dr. Arthur D. Yaghjian received the B.S., M.S., and Ph.D. degrees in electrical engineering from Brown University in 1964, 1966, and 1969, and an Honorary Doctorate from the Technical University of Denmark in 2020. After teaching for a year, he joined the research staff of the National Institute of Standards and Technology (NIST), Boulder, CO in 1971 and transferred in 1983 to the Air Force Research Laboratories, Bedford, MA until 1996 when he became an independent researcher. His early research at NIST helped pioneer the development of probe-corrected near-field antenna measurements for accurately characterizing modern antennas in both the frequency and time domains. More recently, he has extended the spherical-wave near-field antenna theory to the rigorous analysis of the partially coherent fields radiated by the sun and other stars. His research in electromagnetic theory has led to the fundamental determination of electromagnetic fields in spatially dispersive as well as temporally dispersive natural materials and metamaterials. He has derived the definitive microscopic and macroscopic force and energy expressions for both diamagnetic and paramagnetic media. He has contributed significantly to the determination and fundamental understanding of the classical equations of motion of accelerated charged particles. In the area of high-frequency diffraction, he and Robert Shore obtained convenient robust expressions for incremental length diffraction coefficients that are currently used to predict bistatic scattering and reflector antenna performance in commercial high-frequency computer codes. His work with Steven Best on the fundamental characterization of antennas, including the determination of the upper bounds on the bandwidth of complex antennas, has had a major impact on the research and development of modern electrically small antennas. He holds the patent on supergain electrically small antennas. He is an IEEE Life Fellow and has been an IEEE-APS Distinguished Lecturer. He has received the IEEE Electromagnetics award, the IEEE-APS Distinguished Achievement award, four IEEE Schelkunoff prize paper awards, and has written two well-referenced books, one co-authored with Thorkild Hansen.
This is an in-person seminar. If you opt to join via zoom use meeting ID 595 955 6744 Passcode 842444