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Permittivity measurements usinq resonant cavity techniques have been the subject of numerous studies over the past forty years. Conventional cavity perturbation measurements normally use a transmission cavity, sweeper, power detector and an oscilloscope or other instrument to record the resonance curve and thereby provide the necessary information on the resonant frequency and the 0 factor to calculate the permittivity of a sample material placed within the cavity.

A needle-type coaxial probe for the measurement of radio frequency and microwave permittivity of biological samples is studied both theoretically and experimentally. The probe is obtained by a slanted cut, and therefore the radiation aperture is elliptical. Both theoretical analysis and experiments show that the measurement sensitivity is improved with the increased bevel angle of the probe. Calibration results using water and air at low frequencies are in agreement with theoretical calculations. Measurements on three biological samples (sonicated DNA macromolecules, water solutions of protein (the protamine), and in -aminocaproic acid) were made from 1 MHz to 1 GHz. All the measured results are in very good agreement with similar tests obtained from the same materials using a standard probe. The theoretical and experimental results show that the probe improves measurement sensitivity and it facilitates insertion into some test samples. >

This paper presents a modified theory for the measurement of the surface resistivity of thin films, deposited on either thin or thick dielectric substrates; in addition the formulations for the measurements of thin dielectric substrates is derived. The reflection coefficient of a probe in contact with the surface is used to calculate the surface resistivity of the film or else the dielectric constant of the dielectric substrate. The expression giving the reflection coefficient in terms of the surface resistivity of a film on a thin substrate is developed by matching the electromagnetic fields at the aperture of the coaxial line. Experimental results of conductive thin films on thin substrates (indium tin-oxide thin film deposited on polyethylene substrates) and dielectric substrates without films are reported from DC to 4 GHz. The experimental results calculated with the derived expressions and the measured reflection coefficients are in agreement with surface resistivity values quoted by the manufacturer of the various test samples used.

Several formulas for the calculation of the admittance of open-ended coaxial probes from the complex permittivity, e, of the measured medium and the dimensions of the probe are presented. The inverse problem, calculation of e from the measured admittance of the probe, is also studied in detail. These formulas are discussed and compared in terms of numerical calculations. New universal diagrams of solutions of these problems are presented which are both convenient and useful for practical measurements. Some distinguishing features of the relationship between e of the measured medium and the admittance of the probe are discussed.

A detailed analysis of the five-port reflectometer is presented in this paper. The possibility and application limitation of using a five-port to measure complex reflection coefficients is discussed and the related design consideration is derived. From the poiut of view of minimum measurement error, an optimized, multi-octave five-port circuit is suggested and realized by ordinary microwave integrated circuit technology. Some measurement results are reported to prove the above analysis and design consideration.

This paper examines the edge effects of introducing a dielectric test cylinder with a test material into a cavity via a metallic support tube extending outside the cavity. A first-order perturbation theory is used for this metallic hole containing two different concentric dielectric materials. The Galerkin method is used to determine the amplitudes of numerous evanescent modes which exist in such composite hole geometries. Comparisons are made with the effects produced by a simple hole in which a single dielectric is postulated inside the metallic support tribe. The effects of the composite hole on the measurement of the dielectric properties of materials are given.

This paper presents a simple method for calibrating any practical multiport reflectometer by means of four reflection standards with known complex reflection coefficients. It is shown that these four standards can be such that their reflection coefficient modulus = 1. Computer simulation proves that no singularity appears for both ideal and nonideal five- and six-port reflectometer in a wide range of phase distribution of reflection coefficients. A group of calibration results for a practical simple six-port is fisted to show this calibration procedure; by the use of these calibrated network parameters, some measurement results are presented and compared with the values obtained at the National Bureau of Standard, U.S.A. Both computer simulation and experimental results show that the numerical singularities which may be encountered in multiport calibration procedures are not an intrinsic properties of multiport but from related mathematical treatment.

Very little work has been done in the past on the use of microwave plasmas for the desulfurization of oil products. This paper presents the measured desuffurizaiion levels on a diisopropyl disulfide oil solution containing 5.2% by weight of sulfur. Complete desulfurization was obtained, using either hydrogen or helium plasmas at atmospheric pressures.The estimated cost to completely desulfurize I metric ton of oil containing 5,2% by weight of sulfur is about $20.00 by the use of this new technology.

A new technology for producing large volume microwave plasmas is introduced, Microwave energy is coupled into the plasma by means of a slow wave structure, and plasma volumes well in excess of 1000 cm3 can readily be achieved with 2.5 kW of microwave power at 2.45 GHz. General operating characteristics and some experimental data are presented.

In an attempt to understand the factors involved in failure to duplicate previous success in freezing and thawing canine kidneys, an analysis of the two ovens used revealed more irregularity of heating within the Litton chamber. In addition, direct measurement after thawing as well as thermography showed that the Litton chamber gave a wider spread in heating than did the Toshiba oven. In order to introduce an indirect way to monitor temperature changes within the chamber during the thawing process, the use of a resonant perturbation technique is described. Such measurements are noncontact and depend on the average temperature load in the oven. This method can be used to control automatically the rate of average temperature rise and regularize the heat cycle and time. Connected to a programmed microprocessor it would allow the design of ovens which could ignore the problems of magnetron sensitivity. The concentration of Me 2 SO in the solution has been demonstrated to affect the curve of thaw and the size of the kidney is also of great importance. If thawing is stopped at 0 °C, deep and uniform thawing occurs which may obviate the thermal runaway seen when the thaw is brought to higher temperature.

An alternative nonlinear method to calibrate the six-port reflectometer is developed. Using this method four standards and iteratrive procedure are needed to calibrate the reflectometer.Experimental results show that this method coverges very rapidly, provides a good accuracy in calibration parameters and at the same time avoids degenerate solutions which produce unwanted singularities in the mesurement.