Numerical evaluation of the scattering matrix for raindrops

Summary form only given. The signal used in classic radar is based on two informational parameters: the amplitude and the frequency. They allow the detection of the target as a dot, if the amplitude surpasses a certain threshold and mobility through Doppler frequency evaluation. In order to obtain more information, the processed signal should include a large number of parameters obtained from frequency, phase or polarization modulation. The paper investigates the polarimetric signature of the targets with a cross section less than the wavelength of the incident electromagnetic field. This field is analytically described by using a particular form of bi-complex quaternions. As a result, the target is defined by several parameters, which form the scattering matrix (the target signature). Their values depend on the range radar-target, the mobility and the geometric properties of the target. The paper presents the equations used to define cross section of the raindrops as a function of the rain intensity. It also presents the mathematical fundamentals of the numerical method allowing the scattering matrix evaluation. This kind of object are investigated with an incident electric field having two orthogonal components (linear or elliptic). As a result, the scattering matrix for real targets has three complex components. The paper also presents the results obtained from scattered field of the different kinds of raindrops (equivalent sphere diameter less than 8 mm)