Design of broad-band radar-absorbing materials for large angles of incidence

A numerical technique, called the (modified) Powell method, is used to design radar-absorbing materials (RAMs) made up of several dielectric layers, usually on top of a conducting (ground) plane. The absorption of RF energy occurs mostly in the last layer. The other layers are used to match the wave impedance of the RAM to that of the medium on which the radiation is incident, for the desired angles of incidence, frequencies, and polarizations. The technique is very flexible, allowing the design of RAMs tailored for specific applications or general use. One important example is the design of RAMs that can maintain a minimum absorption rate from normal to almost grazing incidence, over a specified frequency bandwidth.