Electromagnetic Wave Absorbers

Carbonized Silk Fiber Mat: a Flexible and Broadband Microwave Absorber, and the Length Effect

“…Since the booming development of electronic devices and the ensuing electromagnetic (EM) wave pollution, there exists an urgent demand for EM absorbers with high strength, lightweight, broad bandwidth, and strong attenuation performance. , Traditional magnetic materials (e.g., carbonyl iron, , ferrite, metal alloys, etc.) are widely used as microwave absorbers due to their prominent magnetic loss at high frequency.…”

The Intersection of Computational Design and Wearable‐Optimized Electrospun Structural Nanohybrids for Electromagnetic Absorption

“…and 𝜖 0 ≈8.85 × 10 −12 F m −1 are the intrinsic impedance, permeability, and permittivity of free space, respectively). [30] Therefore, R is proportional to the mismatch between Z out and the input impedance (Z in ) (i.e., the opposition to current flow in the transmission line) as: [29,31,32]…”

“…[ 22,29 ] Since the wave impedance approaches the intrinsic impedance of the homogeneous medium that the wave propagates through, in the case of free space Z out = Z 0 = η 0 = $$\sqrt {{\mu }_0/{\varepsilon }_0} $$ = 377 Ω ( Z 0 , μ 0 = 4 π × 10 −7 H m −1 , and ε 0 ≈8.85 × 10 −12 F m −1 are the intrinsic impedance, permeability, and permittivity of free space, respectively). [ 30 ] Therefore, R is proportional to the mismatch between Z out and the input impedance ( Z in ) (i.e., the opposition to current flow in the transmission line) as: [ 29,31,32 ] $$$$\begin{equation}R\ = {{{\Gamma}}}^2\ = \left( {\frac{{{Z}_{in} - {Z}_{out}}}{{{Z}_{in} + {Z}_{out}}}} \right){\ }^2\end{equation}$$$$where Γ is the reflection coefficient. Z in at the front surface of the assumed transmission line composed of i impedance elements can be calculated as: $$$$\begin{equation}{Z}_i = {\eta }_i\ \frac{{{Z}_{i - 1} + {\eta }_i\tanh \left( {{\gamma }_{i} \ell_{i}} \right)}}{{{\eta }_i + {Z}_{i - 1}\tanh \left( {{\gamma }_{i} \ell_{i}} \right)}}\end{equation}$$$$…”

Theory, Modeling, Measurement, and Testing of Electromagnetic Absorbers: A Review

“…These movements generate heat due to the resistance encountered by these charges. The second part, 1 2 ωεE 2 captures power dissipation resulting from dielectric losses (ε). Dielectric materials are insulators that can store energy as a field when subjected to an applied E field.…”

“…However, they are not perfect insulators and experience energy loss as molecular or atomic movements occur within them, leading to heat generation. Lastly, the third part, 1 2 ωμH 2 represents power dissipation caused by magnetic losses (μ). Magnetic materials, like ferromagnetic substances, have the ability to store energy in a field when exposed to an applied magnetic field (H).…”