ASTM D7449/D7449M-14

Standard Test Method for Measuring Relative Complex Permittivity and Relative Magnetic Permeability of Solid Materials at Microwave Frequencies Using Coaxial Air Line

1.1 This test method covers a procedure for determining relative complex permittivity (relative dielectric constant and loss) and relative magnetic permeability of isotropic, reciprocal (non-gyromagnetic) solid materials. If the material is nonmagnetic, it is acceptable to use this procedure to measure permittivity only.

1.2 This measurement method is valid over a frequency range of approximately 1 to over 20 GHz. These limits are not exact and depend on the size of the specimen, the size of coaxial air line used as a specimen holder, and on the applicable frequency range of the network analyzer used to make measurements. The size of specimen dimension is limited by test frequency, intrinsic specimen electromagnetism properties, and the request of algorithm. For a given air line size, the upper frequency is also limited by the onset of higher order modes that invalidate the dominant-mode transmission line model and the lower frequency is limited by the smallest measurable phase shift through a specimen. Being a non-resonant method, the selection of any number of discrete measurement frequencies in a measurement band would be suitable. The coaxial fixture is preferred over rectangular waveguide fixtures when broadband data are desired with a single sample or when only small sample volumes are available, particularly for lower frequency measurements

1.3 The values stated in either SI units of in inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore each system shall be used independently of the other. Combining values from the two systems is likely to result in non conformance with the standard. The equations shown here assume an e+jωt harmonic time convention.

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.

ASTM International [astm]

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