ASTM D2520-95

Design calculations for such components as transmission lines, antennas, radomes, resonators, phase shifters, etc., require knowledge of values of complex permittivity at operating frequencies. The related microwave measurements substitute distributed field techniques for low-frequency lumped-circuit impedance techniques.

Further information on the significance of permittivity may be found in Test Methods D 150.

These test methods are useful for specification acceptance, service evaluation, manufacturing control, and research and development of ceramics, glasses, and organic dielectric materials.

FIG. 1 Standing Wave Established Within Empty Shorted Waveguide

1.1 These test methods cover the determination of relative (Note 0) complex permittivity (dielectric constant and dissipation factor) of nonmagnetic solid dielectric materials. Note 0The word "relative" is often omitted.

1.1.1 Test Method A is for specimens precisely formed to the inside dimension of a waveguide.

1.1.2 Test Method B is for specimens of specified geometry that occupy a very small portion of the space inside a resonant cavity.

1.1.3 Test Method C uses a resonant cavity with fewer restrictions on specimen size, geometry, and placement than Test Methods A and B.

1.2 Although these methods are used over the microwave frequency spectrum from around 0.5 to 50.0 GHz, each octave increase usually requires a different generator and a smaller test waveguide or resonant cavity.

1.3 Tests at elevated temperatures are made using special high-temperature waveguide and resonant cavities.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.