Broad Band Electromagnetic Absorption of Flexible Foils in the Microwave Range

Foils filled with conductive and magnetic materials are developed for absorption of microwaves. The foils have a thickness of 0.5 - 1.5 mm and a basic composition of 25 wt.% polyethylene, 9 wt.% carbon, and 66 wt.% inorganic filler of very different nature. The absorbed power is determined from measurements of reflection and transmission with a closed coaxial measuring technique in the frequency range of 40 MHz to 1 GHz. Transmission measurements are carried out from 700 MHz - 18 GHz and 50 - 75 GHz. Foils with thicknesses of about 1 mm absorb more than 30% of the incident power.