Cavity perturbation, dielectric measurements

Bengtsson, N. and Risman, P. 1971. Dielectric properties of foods at 3 GHz as determined by a cavity perturbation technique. Measurement on food materials. Journal of Microwave Power. 6(2) 107-123. 

A method which circumvents many of the disadvantages of the transmission line and cavity perturbation technique was pioneered by Stuchley and Stuchley (1980). This technique calculates the dielectric parameters from the microwave characteristics of the reflected signal at the end of an open-ended coaxial line inserted into a sample to be measured. This technique has been commercialized by Hewlett Packard with their development of a user-friendly software package (Hewlett Packard 1991) to be used with their network analyzer (Hewlett Packard 1985). This technique is outstanding because of its simplicity of automated execution as well as the fact that it allows measurements to be made over the entire frequency spectrum from 0.3 MHz to 20 GHz. 

The application of microwave contactless techniques to the complex permittivity measurements of organic semiconductors is briefly discussed. Special attention is paid to the cavity perturbation technique of Buravov and Shchegolev and the dielectric resonance technique of Jaklevic and Saillant. 

Recently, Grigera et al. (28) performed dielectric measurements by the cavity perturbation technique in the region of... 

The microwave fi equency conductivity and dielectric constant were measured using the cavity perturbation technique [90,114,142,143]. The resonant cavity used was cylindrical with a TMoio frequency of 6.5 GHz. The entire cavity is inserted into a dewar filled with He gas to provide a temperature range of 4.2-300 K. Alternatively, the microwave fi-equency conductivity and dielectric constant may be measured using a microwave impedance bridge [144]. 

The thermal conductivity was determined by laser-flash method (LFA447, Netzsch, German) with billets dimension of (pl2.7mmx2.5mm. The dielectric loss (land) was measured at IMHz by the perturbation meth(xl using a cavity resonator and a vector network analyzer (HP-4294A). 

Another method to utilize microwaves for the measurement of electronic processes in nonpolar dielectrics could make use of the fact that the resonance frequency of a microwave cavity depends on the electron concentration present in the cavity. At low ionization densities, perturbation theory is applicable (Slater, 1946), and the shift in frequency, Af, is proportional to the electron density, n i. 

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