Ferrite grid electromagnetic wave absorbers

The wideband characteristic of a novel ferrite grid electromagnetic wave absorber is presented. Calculation shows that the grid absorber suppresses reflection ⩽-20 dB from 30 to 700 MHz, and ⩽-15 dB up to 1000 MHz. It is shown that an RF anechoic chamber fitted with the grid absorber satisfies the FCC standard. By combining the grid structure with appropriate rubber ferrite and low-permittivity dielectric layers, its bandwidth becomes much wider (from 30 to 1700 MHz for ⩽-20 dB). It is also shown that the thickness of lossy dielectric required for suppressing reflection at any frequency above 30 MHz can be greatly reduced by using the grid structure