Conductors, semiconductors and insulators are the main components of almost all RF / microwave electronic equipment. The dielectric properties of insulators will affect the electric field passing through them. In order to design RF components or devices, the dielectric properties of insulators used in the construction of components / devices must be understood in detail. The two main dielectric parameters to be considered are the dielectric constant and loss tangent, or the real and imaginary parts of the complex dielectric constant.

More specifically, a dielectric is an insulating material that will polarize when subjected to an electric field. This phenomenon is called dielectric polarization. Although the permeability of space is usually static (except in the presence of ferromagnetic objects); However, the dielectric constant of space is greatly affected by the gases, liquids and solids in the space filled with materials. As with permeability, the effect of dielectric constant depends on frequency. Therefore, the complex permittivity is measured over the entire frequency range.

Dielectric polarization mechanism

Dipole polarization

Ion polarization

Electron polarization

Atomic polarization

Interface or space charge polarization

Dielectric loss

Relaxation time

Moreover, the dielectric needs to be measured very accurately in order to determine the dielectric constant and loss tangent with a certain accuracy. When testing dielectrics, there are many physical factors to consider, because electrical phenomena will be affected by dielectric properties, and electromagnetic waves have physical dependent parameters (i.e. wavelength). This means that some types of dielectric microwave measurement methods are better than others in specific types of dielectrics and applications. The basis of dielectric characterization and testing is that when the electric field or electromagnetic wave passes through the dielectric and the environment around the dielectric is controlled, sensitive measuring equipment can detect the change influence of the dielectric on the electric field and wave.

Precautions for dielectric measurement

Actual dielectric size / size

Can it be measured as a sample?

Full sample

Thin sample

Ultrathin sample

liquid

Gas

Does the test have to be non-destructive or can it be destructive?

What frequencies need to be measured

Banded

broadband

narrowband

Single frequency (resonance)

What are the measurement accuracy requirements?

Is the dielectric constant high or low?

Is the dielectric loss high or low?

Due to the limited bandwidth, geometry, fixture, dielectric sensing range and other physical factors of dielectric measurement technology, there are many methods of measuring dielectric. The method used depends on the dielectric under study and bandwidth requirements. For the full wave field simulator, obtaining broadband dielectric properties from the lowest frequency to the highest frequency of interest can help.

Microwave measurement method and application frequency of dielectric

Echo Wall mode

Many of these methods require sophisticated transmission lines, such as coaxial components, precision coaxial connectors, waveguides and planar transmission lines, especially those ranging from hundreds of MHz to more than 100000 MHz. Some methods, such as microwave or millimeter wave free space dielectric measurement, require settings using highly directional antennas, coaxial or waveguide interconnections, and vector network analyzers.