Adjustable Resonant Cavity for Measuring the Complex Permittivity of Dielectric Materials
D. Gershon,a J. P. Calame,b Y. Carmel, and T. M. Antonsen, Jr.
Institute for Plasma Research, University of Maryland, College Park, MD 20742, USA
Review of Scientific Instruments 71 [8], 3207 (2000)
ABSTRACT. An adjustable resonance cavity was developed to measure the complex permittivity of dielectric materials. The cavity has an inner diameter of 16.400 cm and an inner height of 2.54 cm. The aluminum stationary wall holder was positioned about 10.8 cm above the top of the cavity. It was fixed into place by three 1.27-cm-diam linear shafts. By suspending from the wall holder, the movable wall moved vertically by sliding on 1.27 cm bore-closed ball bushings. By turning a 1 in.-12 nut, the movable wall could be positioned so that the cavity height equaled the height of the sample. Therefore, this enables the measurement of the permittivity of samples with heights between 0.88 and 1.91 cm and radius between 1.27 and 3.18 cm. The complex permittivity of the sample was calculated based upon the sample dimensions, central frequency of TMono modes, and Q factor of the resonance curve using an exact solution. The complex permittivity was measured at the three lowest modes, where the frequency span is 1-4 GHz.
This research was funded by the Structural Ceramics Division, Air Force Office of Scientific Research.
aCurrent address: Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124.
bAlso at: Naval Research Laboratory, Vacuum Electronics Branch, 4555 Overlook Avenue, SW, Washington, DC 20375.