Active Dallenbach radar absorber

Conventional radar absorbent materials (RAM) fall into two main types based on the Salisbury screen and the Dallenbach layer or their multi-layer counterparts. They operate by absorbing the incident electromagnetic energy and converting it into heat. An alternative approach is to use an active absorber, such as the phase-switched screen (PSS), which achieves an apparent reduction in the level of the electromagnetic energy reflected from its surface by using binary phase modulation to redistribute it over a bandwidth which is much wider than that of the receiver. To date, all the reported PSS implementations have used thin active layers consisting of arrays of PIN diode-loaded resonant elements and hence they may be considered as active versions of the Salisbury screen or Jaumann absorber topologies. In this paper, we consider an alternative route to the PSS, based on a medium with switchable material parameters. This may therefore be regarded as an active version of the Dallenbach absorber