Measured complex permittivity of walls with different hydration levels and the effect on power estimation of twri target returns

Abstract

In this paper, measured results for complex permittivity of some commonly used building walls under different hydration (wetness) levels are presented and a simple hybrid measurement and electromagnetic modeling approach for the estimation of power returns from targets located behind walls in various through-the-wall radar imaging (TWRI) scenarios is discussed. The radar cross section (RCS) of some typical targets of interest, such as an AK47 assault rifle and human, are first investigated in free-space using numerical electromagnetic modeling. A modified radar range equation, which analytically accounts for the wall effects, including multiple reflections within a given homogeneous or layered wall, is then employed in conjunction with wideband measured parameters of various common wall types, to estimate the received power versus frequency from modeled targets of interest. The proposed technique, which can be helpful in TWRI dynamic-range system design consideration, is, in principle, applicable to both bistatic and monostatic operations. The results for various wall types, including drywall, brick, solid concrete, and cinder block, the latter two under both wet and dry conditions, are presented.