The Relationship of Permeability and Permittivity at the Perfect Matching Point of Electromagnetic Wave Absorption for the Absorber Filled by Metallic Magnetic Particles

Abstract

The electromagnetic wave absorption properties of flake-shaped carbonyl-iron/paraffin composites with various volume concentrations were calculated by the measured complex permeability and permittivity. The complete electromagnetic wave absorption was searched for the volume concentration of 0.125, 0.15 and 0.20 at 5.8, 4, and 3.6 GHz, respectively. The permittivity is much larger than the permeability at the complete absorption frequency points. Based on the origin of the absorbing peaks, the contour map displaying the relationship between the complex permittivity and complex permeability at the perfect matching point was developed. The complex permittivity obtained from the contour map basically agrees with the experimental data for a given complex permeability. Hence, the contour map can be used to design the absorber for obtaining the excellent electromagnetic wave absorption.

A theoretical investigation on the quarter-wavelength model — part 1: analysis

“…In QWM, it has been wrongly claimed [26,30] that the minima of RL(dB) occur at the energy difference of beams r and t. But it is clearly shown here that RL(dB) is related to phase difference and not to energy difference. The amplitude of beam b can be enhanced or reduced from the superposition of beams r and t. Indeed, the amplitude of beam b is related to that part of the incident microwave energy returned to the open space, but the energy of beam b is not equal to the sum of energy of beams r and t. All the other parts of the incident microwaves not reflected have been absorbed by the film.…”

Microwave absorption and bandwidth study of Y2Co17 rare earth soft magnetic alloy with easy-plane anisotropy

“…At this time, the two kinds of electromagnetic waves will produce destructive interference at the front interface, and the RL will have a minimum value, forming a strong absorption peak. The condition that the thickness of the absorber is equal to an odd multiple of λ /4 is [32] t m = nc The smaller the sum of the electromagnetic wave amplitudes at the front interface is, the more energy the absorber absorbs, and the smaller the RL (the larger the absolute value). It can be seen from Fig.…”

Microwave absorption properties of rare earth alloy Nd2Co17@C/Na2SiO3 composite at elevated temperature (293–723 K) in the X band

“…This phenomenon can be attributed to the decrease of the complex permeability and the increase of the complex permittivity with the increase of temperature, and thus resulting in an undesirable impedance matching performance and a deteriorated microwave absorption performance. Additionally, according to the interface reflection model, when a strong absorption peak appears, the relationship between the thickness of the absorber and the peak frequency can be expressed as: t m = nc 4fm √ |µrεr| [30]. We know that the thickness of the absorber is inversely proportional to the |µ r ε r | value.…”