Dielectric Constant and Dissipation Factor - ASTM D2520
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ASTM D2520 is used to test materials over the microwave frequency spectrum from 0.5 to 50 GHz.
Testing Methods
| Method |
Description |
| A |
Used for specimens precisely formed to the inside dimension of a waveguide. |
| B |
Used for specimens of specified geometry that occupy a very small portion of the space inside a resonant cavity. |
| C |
Uses a resonant cavity with fewer restrictions on specimen size, geometry, and placement than in Test Methods A and B. |
Dielectric Constant (Relative Permittivity)
The ratio of capacitance of a capacitor with test material as the dielectric to the capacitance of a capacitor with a vacuum as the dielectric. For materials that are to be used to insulate electrical components the dielectric constant should be low. For materials that are to be used as a dielectric in a capacitor, the dielectric constant should be high so that the capacitor dimensions can be minimized. The dielectric constant can be calculated using:
ε = Cs / Cv
where Cs is the capacitance with the specimen as the dielectric,
and Cv is the capacitance with a vacuum as the dielectric.
Dissipation Factor
The ratio of the power dissipated in the test material to the power applied. Equal to the tangent of the loss angle, or the cotangent of the phase angle. The dissipation factor can be calculated using:
D = tan δ = cot θ = 1 / (2π f RpCp)
where δ is the loss angle,
θ is the phase angle,
f is the frequency,
Rp is the equivalent parallel resistance,
and Cp is the equivalent parallel capacitance.
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