Analysis of Conduction Noise Attenuation by Magnetic Composite Sheets on a Microstrip Line by the Finite Element Method
Conduction noise attenuation by magnetic composite sheets along a microstrip line has been analyzed by using an electromagnetic
field simulator that employs the finite element method. The simulation model consists of a microstrip line with planar input/output
ports and noise absorbing materials of large magnetic loss (magnetic composite sheets containing iron flake particles as absorbent
fillers). The input port is excited by a TEM-mode wave with a characteristic impedance of 50 Ω. Reflection and transmission
parameters (S11 and S21) and power loss are calculated as a function of frequency with variation of the sheet size and thickness. The simulated values
are in good agreement with experimental results and the estimated size dependency of power absorption is consistent with transmission
line theory. It is proposed that the simulation technique can be effectively used in the design and characterization of noise
absorbing materials in high-frequency transmission lines.
Keywordsmagnetic materials-powder processing-electrical properties-computer simulation-noise absorbers
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ABSTRACT: For the aim of wide-band noise absorbers with a special design for low frequency performance, this study proposes conductive indium-tin oxide (ITO) thin films as the absorbent materials in microstrip line. ITO thin films were deposited on the polyimide film substrates by rf magnetron cosputtering of In2O3 and Sn targets. The deposited ITO films show a typical value of electrical resistivity ( ∼ 10−4 Ω m) and sheet resistance can be controlled in the range of 20–230 Ω by variation in film thickness. Microstrip line with characteristic impedance of 50 Ω was used for determining their noise absorbing properties. It is found that there is an optimum sheet resistance of ITO films for the maximum power absorption. Reflection parameter (S11) is increased with decrease in sheet resistance due to impedance mismatch. On the while, transmission parameter (S21) is decreased with decrease in sheet resistance due to larger Ohmic loss of the ITO films. Experimental results and computational prediction show that the optimum sheet resistance is about 100 Ω. For this film, greater power absorption is predicted in the lower frequency region than ferrite thin films of high magnetic loss, which indicates that Ohmic loss is the predominant loss parameter for power absorption in the low frequency range.
Journal of Applied Physics 07/2010; 108(2):024904-024904-6. DOI:10.1063/1.3456515 · 2.18 Impact Factor
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ABSTRACT: Noise absorbing properties of two kinds of magnetic thin films (one is electrically conductive Co-Zr-O granular thin film and the other is Ni-Zn ferrite thin film with high electrical resistivity) are analyzed by the finite element method (FEM) with various film thicknesses. For the Ni-Zn ferrite film with high electrical resistivity (∼2 × 10 2 Ωm), a low reflection parameter (S11) value is predicted, and the value does not significantly change with increased film thickness up to 10 μm. However, the transmission parameter (S21) is reduced with increased film thickness due to increased power absorption by magnetic loss. For the Co-Zr-O thin films with low electrical resistivity (∼1.6 × 10−5 Ωm), however, reflection signal is increased with increased film thickness due to diminished sheet resistance of the thin film. Transmission loss is not very sensitive to the thickness of the conductive film. Large power absorption is, therefore, predicted for conductive film of smaller thickness. It is concluded that film thickness is an important control parameter for the achievement of a highly absorptive thin film with increased electrical conductivity.
Metals and Materials International 10/2011; 17(5). DOI:10.1007/s12540-011-1018-y · 1.58 Impact Factor
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