IEC 62810-2015 pdf Cylindrical cavity method to measure the complex permittivity of low-loss dielectric rods

This International Standard relates to a measurement method for complex permittivity of a dielectric rod at microwave frequency. This method has been developed to evaluate the dielectric properties of low-loss materials in coaxial cables and electronic devices used in microwave systems. It uses the TM 01 0 mode in a circular cylindrical cavity and presents accurate measurement results of a dielectric rod sample, where the effect of sample insertion holes is taken into account accurately on the basis of the rigorous electromagnetic analysis. In comparison with the conventional method described in IEC 60556 [2] 1 , this method has the following characteristics: • the values of the relative permittivity ε ‘ and loss tangent tan d of a dielectric rod sample can be measured accurately and non-destructively; • the measurement accuracy is within 1 ,0 % for ε ‘ and within 20 % for tan d ; • the effect of sample insertion holes is corrected using correction charts presented;
where correction factors C 1 and C 2 , due to the sample insertion holes and errors included in the perturbation formulas, are calculated numerically by using the Ritz-Galerkin method [3][5], as shown in Figure 2 and Figure 3, and the corresponding data are listed in detail in Table 1 , 2, and 3. The missing data of C 1 and C 2 can be obtained by interpolation or extrapolation from the tables. The correction factors shown in these figures are calculated for the cavity with D = 76,5 mm, H = 20,0 mm, d 2 = 3,0 mm, and g = 1 0,0 mm, where the resonant frequency is about 3 GHz. C 1 is also used for a cavity having the same aspect ratios as H/D, d 2 /D and g/D.
Figure 4 shows a schematic diagram of two equipment systems required for microwave measurement. For the measurement of dielectric properties, only the information on the amplitude of transmitted power is needed, that is, the information on the phase of the transmitted power is not required. Therefore, a scalar network analyser can be used for the measurement shown in Figure 4a. However, a vector network analyser, as shown in Figure 4b, has an advantage in precision of the measurement.