Determination of the Forward Electromagnetic Coupling Radius in Chaff Cloud

Chaff cloud is a passive jammer that is widely used in many tactical applications. It contains huge numbers of metallic fibers to produce a strong echo. However, electromagnetic (EM) scattering estimation for the chaff cloud is a challenging task since complex EM coupling between chaff elements needs to be taken into account. Actually, if the distance and the angle between two chaff elements are large enough, the EM coupling becomes ignorable. This letter presents an estimation method of the EM coupling radius to designate a region, out of which EM coupling effect can be ignored. A current attenuation formula is first proposed to indicate the relationship between the induced surface currents of any two chaff elements. Using Dijkstra's algorithm, we then find the coupling paths with the weakest attenuation. The EM coupling radius is finally determined by measuring the distance between two ends of the selected paths. Simulation results show that the averaged EM coupling radius is 3.7 times wavelength of the radar in our discussions.