Response of radar cross section reduction bandwidth to the dielectric constant

RF stealth is the most important feature of the 5th generation fighters, and although 70–80% of RF stealth is achieved by shape morphing, and only 20–30% is achieved by Radar Absorption Materials (RAM) the development of RAM is still of great interests. Because manufacturing of RAM is a challenging task, the necessity of precision control in dielectric constant ε deserves deeper understanding. In this article we investigate the effect of ε on the performance of RAM by simulating the RCS of a 1 × 1 × 0.01 m³ perfect conductor metal plate, and one that is covered with 4cm thick RAM. The comparison standard RAM1 is designed to operate in microwave frequency, and the real and imaginary part of ε of RAM1 is varied to observe the actual RCS reduction changes. We found despite the ε of RAM1 is optimized for microwave band; the actual RCS reduction effect can also be observed in the VHF-UHF band, where wavelength is much larger than the object. Changing the real part of the ε usually means changing the impedance of the RAM, and changing the imaginary part of ε usually means changing the loss term of the RAM, but the real RCS simulation show much complicated unexpected resonance behavior. The simulation results indicate precision tuning of ε may not be as important as previously believed, and controlling the resonance condition play a more important role.