Radar cross section (RCS) of perfectly conducting (PEC) thin wires and its application to radar countermeasure: Chaff

Abstract

In electronic warfare, active and passive countermeasures are used to jam threat RF radars. While electronic jamming pods are accepted as an active one, chaff is accepted as a passive countermeasure that consists of millions of perfectly conducting thin metallic wires, dipoles. The aim of this thesis is to first implement Van Vleck’s Methods A and B [1], Tai’s Variational Method [2] and Einarsson’s Direct Method [3] to get radar cross section (RCS) of a dipole and then apply the results to calculate RCS of designed chaff cartridges. The ultimate goal is to suggest more effective passive countermeasure system than commercially available ones. In this thesis, performances of these methods are evaluated. According to these evaluations, Van Vleck’s Method B and Einarsson’s Direct Method are selected for calculating RCS of chaff cartridges. Performance of RR-178 (XN-2) commercial chaff cartridge is compared with three different suggested designs. For each of these designs, 2 to 20 GHz frequency interval is divided into three or six equal sub-frequency intervals and for these intervals particular chaff cartridges with different dipole lengths and numbers are proposed. In terms of total dipole length in the cartridges, instead of 88775 meters dipoles that is used in RR- 178 (XN-2), by using chaff cartridges of third proposed design, in average only 25300 meters dipoles are used while providing more flat and equal average RCS value for 2 to 20 GHz frequency interval. Moreover, for the stated frequency interval, if total dipole length for the chaff cartridges of RR-178 (XN-2) and third proposed design keep equal, about 5.2 dB increase in average RCS value is obtained. Analysis of these results shows that designed chaff cartridges are more effective than commercial ones if the designed ones are used together with compatible Radar Warning Receiver (RWR) and Dispensing System.