Standard Active Last Updated: Oct 18, 2022 Track Document
ASTM D5568-22a

# Standard Test Method for Measuring Relative Complex Permittivity and Relative Magnetic Permeability of Solid Materials at Microwave Frequencies Using Waveguide

Standard Test Method for Measuring Relative Complex Permittivity and Relative Magnetic Permeability of Solid Materials at Microwave Frequencies Using Waveguide D5568-22A ASTM|D5568-22A|en-US Standard Test Method for Measuring Relative Complex Permittivity and Relative Magnetic Permeability of Solid Materials at Microwave Frequencies Using Waveguide Standard new BOS Vol. 10.02 Committee D09
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Significance and Use

5.1 Design calculations for radio frequency (RF), microwave, and millimetre-wave components require the knowledge of values of complex permittivity and permeability at operating frequencies. This test method is useful for evaluating small experimental batch or continuous production materials used in electromagnetic applications. Use this method to determine complex permittivity only (in non-magnetic materials), or both complex permittivity and permeability simultaneously.

5.2 Relative complex permittivity (relative complex dielectric constant), εr*, is the proportionality factor that relates the electric field to the electric flux density, and which depends on intrinsic material properties such as molecular polarizability, charge mobility, and so forth:

 where: ε0 = the permittivity of free space, D→ = the electric flux density vector, and E→ = the electric field vector.

Note 1: In common usage the word “relative” is frequently dropped. The real part of complex relative permittivity (εr) is often referred to as simply relative permittivity, permittivity, or dielectric constant. The imaginary part of complex relative permittivity (εr) is often referred to as the loss factor. In anisotropic media, permittivity is described by a three dimensional tensor.

Note 2: For the purposes of this test method, the media is considered to be isotropic and, therefore, permittivity is a single complex number at each frequency.

5.3 Relative complex permeability, μr*, is the proportionality factor that relates the magnetic flux density to the magnetic field, and which depends on intrinsic material properties such as magnetic moment, domain magnetization, and so forth:

 where: μ0 = the permeability of free space, B→ = the magnetic flux density vector, and H→ = the magnetic field vector.

Note 3: In common usage the word “relative” is frequently dropped. The real part of complex relative permeability (μr) is often referred to as relative permeability or simply permeability. The imaginary part of complex relative permeability (μr) is often referred to as the magnetic loss factor. In anisotropic media, permeability is described by a three dimensional tensor.

Note 4: For the purposes of this test method, the media is considered to be isotropic, and therefore permeability is a single complex number at each frequency.

5.4 Relative permittivity ((relative dielectric constant) (SIC) κ′(εr)) is the real part of the relative complex permittivity. It is also the ratio of the equivalent parallel capacitance, Cp, of a given configuration of electrodes with a material as a dielectric to the capacitance, Cυ, of the same configuration of electrodes with vacuum (or air for most practical purposes) as the dielectric:

Note 5: In common usage the word “relative” is frequently dropped.

Note 6: Experimentally, vacuum must be replaced by the material at all points where it makes a significant change in capacitance. The equivalent circuit of the dielectric is assumed to consist of Cp, a capacitance in parallel with conductance. (See Fig. 3 of Test Methods D150.)

Note 7: Cx is taken to be Cp, the equivalent parallel capacitance as shown in Fig. 3 of Test Methods D150.

Note 8: The series capacitance is larger than the parallel capacitance by less than 1 % for a dissipation factor of 0.1, and by less than 0.1 % for a dissipation factor of 0.03. If a measuring circuit yields results in terms of series components, the parallel capacitance must be calculated from Eq 5 of Test Methods D150 before the corrections and permittivity are calculated.

Note 9: The permittivity of dry air at 23 °C and standard pressure at 101.3 kPa is 1.000536. Its divergence from unity, κ′ − 1, is inversely proportional to absolute temperature and directly proportional to atmospheric pressure. The increase in permittivity when the space is saturated with water vapor at 23 °C is 0.00025, and varies approximately linearly with temperature expressed in degrees Celsius, from 10 °C to 27 °C. For partial saturation the increase is proportional to the relative humidity.

Scope

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 100 MHz to over 40 GHz. These limits are not exact and depend on the size of the specimen, the size of rectangular waveguide transmission 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. Being a non-resonant method, the selection of any number of discrete measurement frequencies in a measurement band would be suitable. Use of multiple rectangular waveguide transmission line sizes are required to cover this entire frequency range (100 MHz to 40 GHz). This test method can also be generally applied to circular waveguide test fixtures. The rectangular waveguide fixture is preferred over coaxial fixtures when samples have in-plane anisotropy or are difficult to manufacture precisely.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are in inch-pound units and are included for information only. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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