scholarly journals Effect of different permeability on electromagnetic properties of absorbing materials

2018 ◽  
Vol 197 ◽  
pp. 02015 ◽  
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.

Effect of Quenched Speed on Microwave Properties of the NdFeB Nanocomposites

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.

scholarly journals The problems in the quarter-wavelength model and impedance matching theory in analysising microwave absorption material

2021 ◽  
Author(s):  
Ying Liu ◽  
Yue Liu ◽  
Michael GB Drew
Keyword(s):  
Transmission Line ◽  
Microwave Absorption ◽  
Reflection Loss ◽  
Impedance Matching ◽  
Matching Theory ◽  
Transmission Line Theory ◽  
Scattering Parameter ◽  
Quarter Wavelength ◽  
Line Theory ◽  
Absorption 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.

Electromagnetic Properties of Nanometer SiC/CNTs Composite

2009 ◽  
Vol 79-82 ◽  
pp. 349-352 ◽  
Author(s):  
Jian Xun Yao ◽  
Liu Ying Wang ◽  
Gu Liu ◽  
Shao Chun Hua
Keyword(s):  
Microwave Absorption ◽  
Reflection Loss ◽  
Complex Permittivity ◽  
Mass Fraction ◽  
Low Frequency ◽  
Electromagnetic Properties ◽  
Transmission Line Theory ◽  
Microwave Absorption Properties ◽  
Line Theory ◽  
Maximum Reflection Loss

Both the complex permittivity and permeability of nanometer SiC and nanometer SiC/CNTs composite were investigated by Hewlett-Packard 8510B Network Analyzer. The results show that the complex permittivity of nanometer SiC/CNTs composite is much higher than that of nanometer SiC. Reflection curves of nanometer SiC and nanometer SiC/CNTs composite calculated with electromagnetic wave transmission-line theory show that the addition of CNTs at 6 wt%, 12 wt% and 18 wt% in nanometer SiC absorber can improve its microwave absorption properties strongly. There is a relationship between the mass fraction of CNTs and microwave absorption ability. With increase of the mass fraction of CNTs, its microwave absorption ability firstly increased then decreased. From the simulation, it was found that nanometer SiC with 12 wt% CNTs gave the optimum microwave absorption. The corresponding frequency of maximum reflection loss value of nanometer SiC/CNTs composite gradually moves to the low frequency range with increase of thickness. The maximum reflection loss value of nanometer SiC/CNTs composite (CNTs content is 12 wt%) was -25.74dB at the corresponding frequency of 11.60 GHz with a bandwidth under -5 dB (68% absorption) is 7.16 GHz when the thickness is 2.0 mm.

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