Chriss A. Jones

Dielectric characterization of low-loss materials a comparison of techniques

Measurements on low-loss materials using closed and open cavity resonators, and dielectric resonator methods are presented. Results indicate that consistent measurement results can be obtained with a number of well-characterized fixtures. Uncertainties associated with each method are addressed. Measurements also were performed on materials used in previous intercomparisons.

Shielded open-circuited sample holder for dielectric measurements of solids and liquids

This paper presents a technique for permittivity measurements that can be used for either liquids or solid coaxial samples from near dc to gigahertz frequencies. The method uses both a full-mode model of a coaxial open-circuited termination and a capacitive method for permittivity determination. The method requires the use of an impedance bridge and a network analyzer. Measurements indicate good accuracy for the permittivity over a very wide band of frequencies. For high permittivity materials the sample surfaces must be metallized. An uncertainty analysis is also presented.

Dielectric and Magnetic Measurements: A Survey of Nondestructive, Quasi-Nondestructive, and Process-Control Techniques" *

A review of the most common methods for nondestructive permittivity and permeability measurements is presented. Transmission-line techniques, coaxial apertures, open resonators, surface-waves, and dielectric resonator methods are examined. Measurements on bulk, thin materials, and thin films are addressed. Measurement fixtures that can be used as sensors are highlighted. The frequency range of applicability and typical uncertainties associated with each method are addressed.

On RF material characterization in the stripline cavity

We examine the accuracy of the air-filled stripline cavity in measuring the dielectric and magnetic properties of bulk materials in the frequency range of 150-2000 MHz. Measured data on complex permittivity and permeability for several different-sized specimens of dielectric and magnetic materials were compared with reference values obtained using other techniques of known uncertainties. Major differences were noted for both complex permittivity and permeability data, and we largely attribute these to less-than-optimal perturbation of the internal cavity fields by the material specimens under test. The technique is particularly unsuited to measuring the dielectric loss of the higher-permittivity low-loss materials due to energy scatter by the specimen under test. In order to improve measurement accuracy, we suggest guidelines on the range of specimen electric and magnetic volume needed for optimal cavity perturbation.

RF material characterization using a large-diameter (76.8 mm) coaxial air line

We report on the development of a 76.84 mm (3.025 in) diameter coaxial air line system whose purpose is to measure the dielectric and magnetic properties of bulk dielectric and ferrite materials over a frequency range of approximately 0.3 - 1500 MHz. We summarize the relative advantages and disadvantages of using large-diameter coaxial air lines for material characterization and we discuss the particular problems associated with calibrating vector network analyzers in this form of transmission line. We also present broadband measurement data on two lossy materials, including a ferrite-loaded polymer and carbon-loaded concrete.

Permittivity Measurements of Low-Loss Dielectric Materials at 60 GHz

The National Institute of Standards and Technology is developing a Fabry-Perot resonator to measure the permittivity at 60 GHz. The system is designed to operate in a semi-confocal configuration with the ability to adapt the system for high-temperature measurements. This talk will focus on design of the system, mode identification, and measurements of permittivity for three low-loss materials.

Measurement intercomparisons of dielectric and magnetic material characterization

We discuss the results of three NIST-organized intercomparisons of dielectric and magnetic material characterization at RF-microwave frequencies. Two studies used the broadband coaxial air line technique and the third the air-filled stripline resonator. Variability of up to /spl plusmn/25% was evident in the measured data.