Abstract.
Resonator and waveguide methods, as well as the free-space method, are widely
used to determine the electromagnetic parameters of materials (complex
permittivity and permeability). Here a waveguide method is considered that
allows one to determine the parameters of materials in a wide frequency range.
However, there are a number of factors that significantly restrict the
application of this method. Modern measurement equipment is based on a
rectangular metal waveguide in which the Í10
mode propagates. When the waveguide is filled with a material to be
investigated, there always exists an air gap between the sample and the wide
wall of the waveguide, which leads to a sharp jump in the electric field
strength at the boundary between the material of the sample and air and
strongly affects the accuracy in determining the electromagnetic parameters.
This factor is especially manifest when measuring materials with large value of
the real part of the complex permittivity. In the paper, the results of a
numerical experiment are presented on the determination of complex permittivity
by the waveguide method in the centimeter and millimeter ranges. Calculations
are carried out for materials with real part of permittivity ε1
= 10 and tangent loss of tanδ 0.1–0.2. It is shown that even a small air gap
between a sample and the broad wall of the waveguide leads to a jump in the
electric field strength when passing from the material to air and introduces a
significant error to the results of measurements. To reduce this error and
enhance the possibilities of the waveguide method, it is proposed that this gap
be filled with electrically conducting paste. The results of calculations in
the presence of a gap and when the gap is filled with the electrically
conducting paste are compared. For example, for a material with ε1
= 10 and tangent loss of tanδ 0.1, the maximum error of measurements in the
millimeter-wave range in the presence of a gap of 0.1 mm is 5.5% for ε1
and 11 % for tanδ. When the gap is filled with the paste, this error reduces to
0.5% for both ε1
and tanδ.
Key words: complex
permittivity, tangent loss, waveguide method, electrically conducting paste.
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For citation:
M. P.
Parkhomenko, D. S. Kalenov, I. S. Eremin, N. A. Fedoseev, V. M. Kolesnikova,
Yu. L. Barinov. Waveguide method for measuring electromagnetic parameters of
materials in the microwave range and estimating the measurement error.
Zhurnal Radioelektroniki - Journal of
Radio Electronics. 2018. No. 9. Available at
http://jre.cplire.ru/jre/sep18/6/text.pdf
DOI
10.30898/1684-1719.2018.9.6