Simple Derivation of Transfer Functions in Bistatic Scattering Model

We present a simple derivation of the increment of the scattering and impedance parameters among antennas caused by the scattering from a target in an inhomogeneous nonmagnetic reciprocal medium. Although these formulas have been published in the literature, we provide a straightforward and elegant derivation using the electromagnetic (EM) reciprocity theorem and the circuit theory. In this way, we provide a deeper physical insight into the formulas crucial for most microwave imaging (MWI) algorithms.