Theoretical prediction and measurement of the scattering from thin wires with one-dimensional random orientation

Electromagnetic scattering models are used to derive information from radar data of remotely sensed objects. Theoretical model development is based on exactly solving scattering problems introducing approximations in order to be of practical use. In this paper a simple model geometry is taken consisting of a linear array of parallel thin finite length electrically perfect conducting straight wires, or needles, with variable height settings. The electric field integral equation (EFIE) formulation of the scattering from such arrays is solved with the method of moments (MOM). The calculations are verified by in-door anechoic chamber measurement of the mono-static radar cross section of a combination of two parallel needles in function of their mutual distance. Bi-static scatter calculation and measurement results of arrays of 16 and 128 needles with averaging over 32 arrays with randomly chosen heights are presented. The measured results agree well with the calculated ones, be it that they are slightly higher in the 128 needle case, which is attributed to experimental mounting difficulty for such a large number of needles. The needle diameter is 0.5 mm and the length is taken equal to the used radar wavelength of 3 cm for which the radar cross section can be accurately determined. Absolute calibration of the measurement results is based on the measurement of a single isolated needle suspended from a nylon wire of 0.1 mm diameter hanging vertically down, at the measurement spot. This is compared with the result obtained when the measurement is repeated with the needle placed in the center of the foam block that is used in mounting the several needle arrays