Frequency-dispersive resistance of high impedance surface absorber with trapezoid-coupling pattern

Abstract

Resonances of the high impedance surface (HIS) absorber with periodic trapezoid-coupling pattern were studied. The theoretical, numerical, and experimental study showed that a frequency dispersion of the equivalent resistance could break the single resonance limitation. The limitation is induced by the non-dispersive feature of the equivalent resistance in simple patterned HIS absorber. Therefore, multi-resonances originated from the trapezoid-coupling pattern effectively expanded the absorption bandwidth. The proposed absorber had a thickness reduced by 41% and a −15 dB absorption bandwidth broadened by 50% compared with Salisbury screen.

Ab Initio Based Double-Sheeted DMBE Potential Energy Surface for N3(2A″) and Exploratory Dynamics Calculations

“…Although the linear isomer is only slightly endoergic relatively to N( 4 S ) + N 2 , large barriers caused by the spin-forbidden nature of this process are predicted, and hence, this reaction is unlikely to form the azide radical . On the other hand, the formation of N 3 from N( 2 D ) + N 2 collisions is predicted to be highly exothermic while showing small reaction barriers (3 kcal mol –1 for the linear isomer and 7 kcal mol –1 for the cyclic one). Such collisions should also be interesting for studies of the atmosphere because this excited state of atomic nitrogen is copiously formed in the ionosphere via dissociative recombination of NO + and N 2 + .…”

“…The N 3 ( 2 A ″) ground-state potential energy surface (PES) is known experimentally − to have a linear minimum ( 2 Π g ), while a ring isomer of B 1 symmetry has found support on experimental evidence. − Ab initio calculations confirmed this isomer to be stable with respect to both spin-allowed and spin-forbidden decomposition and separated from the linear minima by a barrier of 33 kcal mol –1 . Moreover, its stability in reactions with several atmospheric compounds has been a matter of theoretical investigation. , The stationary structures of six PESs (two of 2 A ″ symmetry, three 2 A ′, and one 4 A ″) have been much studied by Morokuma and co-workers, ,, and previously by other groups ,,, for geometry optimizations, fundamental frequencies, dipole moments, and minima of crossing seams (MSX).…”

“…In fact, Hudson and Moore have proposed the use of linear N 3 as a tracer to follow the abundance of molecular nitrogen in space. The reaction of N 3 formation in solid nitrogen has been considered in many experimental studies at low temperature (10–35 K), − but no evidence of both the cyclic isomer and cyclic/linear reaction pathway has been found, although the cyclic form can be theoretically expected under high energy collisions …”

Miniaturized Polarization Insensitive Metamaterial Absorber Applied on EMI Suppression

“…achieve miniaturized, ultrathin, wideband and polarizationinsensitive absorbers. For example, fractal structure [6], [7], resistor-loaded absorber [8], multilayer structure [9]- [11], resistive film [12], [13], magnetic substrate [14], and so on. However, in these previous works, the assembly procedures might be relatively complex and time-consuming, which usually demand careful soldering, precise layer alignments, and high design and fabrication cost [15].…”

Improvement on RCS reduction using flat lossy focusing reflectors

“…Recently, many studies have dealt with the analysis of resistive gratings and received considerable attention. Resistive grating is constructed of periodic resistive sheet with specific pattern, such as printing frequency selective surface (FSS) with resistive ink [3][4][5], or printing FSS by silk screen printing technique through a photo etched frame with carbon black serum [6][7][8], and it possesses greater control of the grating's reflection characteristic. Besides planar configuration, non-planar applications were also demonstrated using resistive gratings.…”