Development of the Low-Observable Radome Using Composite Sandwich Constructions

Abstract

The radar (radio detection and ranging) is a system that transmits EM (electromagnetic) waves in a given direction, and then detects the same waves reflected back by an obstacle in its path. The radar technology has been improved drastically with the use of high-powered large bandwidth transmitters since the World War II, which makes the stealth technology very important for the survival of the weapon systems, such as aircrafts, warships, and missiles in the modern war. The stealth technology is a sub-discipline of ECM (electronic countermeasures) which covers a range of techniques for weapon systems in order to make them less visible or ideally invisible to the radar. For the stealth performance, the RCS (radar cross section) of weapon systems should be minimized because the distance detected by the radar is inversely proportional to the fourth root of the RCS. RCS is a measurement of the strength of the radar signal backscattered from a target object for a given incident EM wave power to describe the extent to which an object reflects an incident EM wave. There are two methods to achieve the stealth function, that is, to reduce the RCS of weapon systems. One is to absorb the EM wave incident on the fuselage of the weapon system and the other is to transmit some of them through the radome or reflect the rest at the radome surface selectively. In this study, the RAS (radar absorbing structure) absorbing EM waves and the low-observable radome having frequency selectivity were developed using composite materials. The RAS was manufactured by nanocomposite materials having conductive nanoparticles like CNT (carbon nanotube) and its absorption rate of the incident EM waves was more than about 90% in the X-band frequency range (8.2 ~ 12.4 GHz). The low-observable radome was fabricated with composite sandwich constructions composed of FSS (frequency selective surface) and composite materials. The role of FSS composed of a copper foil and a polyimide film is to gi...