Estimation of frequency-dependent parameters of unknown walls for enhanced through-the-wall imaging

In this paper, the frequency dependent constitutive parameters of an unknown wall, when interrogated by a ultra-wideband radar, are estimated using a norm-difference algorithm. In this approach, we first apply a technique based on the time-domain reflectometry (TDR) method, which assumes the wall parameters are constant, to quickly obtain an estimate of the dielectric constant, loss-tangent, and the thickness of the wall. Using the initial estimated parameters, the proposed norm-difference algorithm is then applied to estimate the wall´s constitutive parameters for each frequency step over the entire band of the radar signal. Numerical results are presented to show the effectiveness and efficiency of the proposed frequency domain wall parameter estimation technique.