Over the past two decades, Dr. Darko Kajfez, Professor Emeritus of Electrical Engineering at The University of Mississippi, has studied the theory and measurement of Q Factor (Q stands for quality) for resonant electrical circuits.. In collaboration with graduate students and other faculty in the Department of Electrical Engineering, he published a number of papers on resonant cavities, their characterization, measurement and their temperature behavior. He also published a monogram, Q Factor, which is the first book written solely on theory and measurement of Q factor. It was published by Vector Fields (now called Vector Forum), Oxford, MS in 1994. In this book, he describes a procedure for the precision determination of Q by performing numerical processing of data measured with a Network Analyzer.

Book Q Factor and a microwave resonant cavity

His resonator research is based on the need for an accurate characterization of resonators that are widely used in modern day communications, radars, and other wireless systems, as well as in measurements of material properties. At frequencies below 300 MHz, these resonators take the shape of lumped-element resonant circuits, consisting of an inductance, a capacitance and a resistance. At low microwave frequencies, the resonators are commonly made of coaxial lines or of microstrip transmission lines. At higher microwave frequencies, hollow cavities make good resonators. More recently, microwave and millimeter resonators are being made of temperature-stable dielectric resonators and of high-temperature superconducting materials.

For an accurate characterization of the material properties, the unloaded Q factor must be measured with great precision. The objective of the life-long work by Dr. Kajfez has been to develop techniques for precision measurement of the unloaded Q factor. Recently, he completed a program QZERO for Windows, the purpose of which is to assist in the precision measurement of Q factor with an Automatic Network Analyzer. He distributes the student version of the program free to students and faculty at educational institutions. The requests should be sent to .

A dielectric resonator antenna with a cap for measuring the radiation efficiency

His research is continuing, and current ongoing work is related to evaluation of approaches to aperture coupling of dielectric resonators for the development of new designs for efficient dielectric-resonator antennas. See also the UMEE Research Brief "DIELECTRIC RESONATOR ANTENNA RESEARCH," and the tutorial paper "Q FACTOR MEASUREMENTS, ANALOG AND DIGITAL" at: http://www.olemiss.edu/depts/electrical_eng/darko/rfqmeas2b.pdf