Numerical simulation analyses of reflection loss based on transmission line theory

Abstract It is shown here that many concepts in current mainstream microwave absorption theory are used inappropriately. Reflection loss RL has been used to characterize microwave absorption from material instead of film and the results have been rationalized by impedance matching theory. The quarter-wavelength model states that the reflection of microwaves with wavelength l from a film is minimized if the thickness of the film is m l /4 where m is an odd integer. But we show here that the model is wrong because the phase effects from interfaces have been overlooked. RL is an innate property only for metal-backed film. Impedance matching theory is developed from transmission-line theory for scattering parameter s 11 but cannot be generalized to RL.

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Effect of different permeability on electromagnetic properties of absorbing materials

MATEC Web of Conferences ◽

10.1051/matecconf/201819702015 ◽

2018 ◽

Vol 197 ◽

pp. 02015 ◽

Cited By ~ 1

Author(s):

Riser Fahdiran ◽

Yuliyanti Dwi Utami ◽

Erfan Handoko

Keyword(s):

Transmission Line ◽

Reflection Loss ◽

Single Layer ◽

Electromagnetic Properties ◽

Complex Permeability ◽

Transmission Line Theory ◽

Microwave Frequencies ◽

Microwave Absorbing Properties ◽

Absorbing Materials ◽

Line Theory

In this study, we have simulated and investigated electromagnetic properties of six types materials using a single layer metal backed absorber model that were determined at microwave frequencies 8.2 up to12.4 GHz. The reflection loss was simulated for different thicknesses in the range of 0.85 to 1.05 mm based on the relative complex permeability and permittivity referring to transmission line theory. The optimal microwave absorbing properties was be resulted by A3 sample. The minimum RL of −23.84 dB can be obtained at 10.72 GHz with thin thickness of 0.95 mm. This method paves a new avenue to design magnetic and dielectric absorbing materials.

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Effect of Quenched Speed on Microwave Properties of the NdFeB Nanocomposites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.287-290.193 ◽

2011 ◽

Vol 287-290 ◽

pp. 193-196

Author(s):

Guo Zhi Xie ◽

Xiao Long Song ◽

Bao Shan Zhang ◽

Dong Ming Tang ◽

Jiang Wei Chen ◽

...

Keyword(s):

Network Analysis ◽

Transmission Line ◽

Reflection Loss ◽

Microwave Properties ◽

Electromagnetic Properties ◽

Complex Permeability ◽

Transmission Line Theory ◽

Microwave Absorbing Properties ◽

Melt Spun ◽

Line Theory

The effect of the quenched speed on the microstructure and electromagnetic properties of melt spun Nd3Fe68Co18B11 nanocomposites was investigated. XRD spectra showed that only α-Fe phase can be obtained for both quenched samples. The complex permeability () and permittivity () within 2-18GHz were measured by vector network analysis. By virtue of quenched speed increased, the flake-like Nd3Fe68Co18B11 decreased the value of permittivity while that of permeability slightly changed. According to transmission line theory, the reflection loss was calculated. With thin matching thickness of 1.5mm, The Nd3Fe68Co18B11 composites realized the optimum reflection loss RL=-5.3dB at 3.6GHz and RL=-3.5dB at 3.9GHz for quenched speed 30m/s and 20m/s, respectively. It showed that it is possible to obtain good microwave absorbing properties with appreciated quenched speed for as spun Nd-Fe-B nanocomposites.

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