nfluence of the absorber quality on the size effect threshold

Porous pyramidal absorbers provide radio camouflage of covered surface in a wide frequency band. Size effect manifests itself as a thresholding significant reduction of absorber efficiency with decrease of the covered surface dimensions in wavelengths. Impact of the size effect on the coefficient of power reflection from a metal plate with the absorber in the form of two-dimensional pyramid lattice has been investigated under conditions of pyramidal absorber quality variation. Coefficient of power reflection was determined as the ratio of metal plate’s monostatic radar cross sections in normal to the plate’s surface direction in presence of the absorber on the plate and without the absorber. Quality of the pyramidal absorber was characterized by the coefficient of power reflection of the plane wave, which is normally incident at planar surface of metal object with the absorber. Size effect was observed as a significant exceedance of the reflection coefficient from the plate with the absorber over the reflection coefficient from the planar metal surface with the same absorber. In order to improve the quality of the absorber, dimensions of the pyramids’ bases were reduced and magnetic sublayer of variable thickness was introduced. Calculations have shown that improving quality of the absorber, besides general decrease of reflection from the coated plate, leads to a profound change in type of dependence of the reflection coefficient on the size of the coated plate: as the plate size increases to about the wavelength, the reflection coefficient rapidly decreases to the level, which is characteristic to the coated plane, and then the decaying oscillations of the reflection coefficient around the reached level take place. In fact it means the size effect threshold decreasing to about wavelength with absorber quality improvement. The materials of the article were presented at the All-Russian Scientific Conference "Radiation and scattering of electromagnetic waves RSEMW-2025", June 23-27, 2025, Divnomorskoye vill., Krasnodar Territory, Russia