Measurement of permittivity and permeability of microwave materials

DETAILED DESCRIPTION The invention is described in my thesis titled "Frequency Domain Measurements of Microwave Absorber Design Materials" (AFIT/GE/80D-8), presented to the faculty of the School of Engineering of the Air Force Institute of Technology, Air University, United States Air Force.
The thesis is available from the National Technical Information Service (NTIS) under the AD Number A100764, and is incorporated herein and made a part hereof as though fully set forth.
The ability to design and test radar absorber design materials depends on the capability to accurately measure the intrinsic properties of complex mu and epsilon of the material over a wide frequency range.
There was an earlier project to build a time domain measurement system that could measure complex mu and epsilon parameters of design materials over a frequency range from 0.
1 to 16 GHz.
Traditionally, such measurements have been made at fixed frequencies below 10 GHz using slotted-line and impedance-bridge configurations.
Essentially, the time domain measurement system consists of a sub-nanosecond pulse generator and coaxial line system to hold samples of materials, a wideband sampling oscilloscope, and an electronic system which scans and digitizes the transient response of microwave materials.
The transient response is then Fourier transformed on a Hewlett-Packard 21MX computer to provide frequency domain scattering coefficients.
Further computation provides printouts and graphs of complex mu and complex epsilon as a function of frequency.
Although the time domain system works well, there is a need for a measurement capability of complex permittivity and permeability of candidate design materials at frequencies higher than 16 GHz.
The National Bureau of Standards published a report dealing with radar absorber design material measurement techniques at frequencies above 20 GHz.
One area of the report reviews the existing time domain measurement system and recommends a frequency domain approach as one possible way to extend the mu and epsilon measurement capability into the millimeter frequency range