Free-Space Microwave Characteristics of Natural Rubber Composites Filled With Carbon Black for Microwave Application
A contactless and non-destructive microwave method has been developed to characterize natural rubber composites from reflection and transmission measurements made at normal incidence. Microwave non-destructive testing (MNDT) using free-space microwave measurement (FSMM) system involves measureme...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/5969/1/FK_2004_102%20IR.pdf http://psasir.upm.edu.my/id/eprint/5969/ |
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| Summary: | A contactless and non-destructive microwave method has been developed to
characterize natural rubber composites from reflection and transmission
measurements made at normal incidence. Microwave non-destructive testing
(MNDT) using free-space microwave measurement (FSMM) system involves
measurement of reflection and transmission coefficient in free-space. The
measurement system consist of a pair of spot focusing horn lens antenna, mode
transition, coaxial cables and vector network analyzers (VNA). The inaccuracies in
free-space measurements are due to two main sources of errors. 1) Diffraction effects
at the edges of the material specimen. 2) Multiple reflections between horn lens
antennas and mode transitions via the surface of the sample. The spot-focusing
antennas are used for minimizing diffraction effects and we have implemented free space
TRL calibration technique by establishing three standards, namely, a through
connection, a short circuit connected to each port and a transmission line connected
between the test ports. This calibration along with time domain gating feature of the
VNA can eliminate effects of multiple reflections.In this method, the free-space reflection and transmission coefficients, S1 and SZ1 are
measured for natural rubber composites sandwiched between two Teflon plates of
10.64 mm thickness which act as a half-wave transformer at mid-band. The actual
reflection and transmission coefficient, S1 1 and SZ1 of the natural rubber composites
are then calculated from measured S1 1 and SZ1 by using ABCD matrix transformation
in which the complex permittivity and thickness of the Teflon plates are known.
From the complex permittivity, loss tangent, conductivity, wavelength, velocity and
skin depth can be obtained. Result for natural rubber composites filled with different
concentrations of carbon black are reported in frequency range 9-1 1 GHz. |
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