RECONFIGURABLE RADAR ABSORBING STRUCTURE APPLIED TO THE ANTENNA RADAR CROSS SECTION REDUCTION

Abstract

An active reconfigurable radar absorbing structure (RAS) with the pin diode was proposed to reduce the radar cross section (RCS) of antenna. The operating states of the RAS reflector can be switched by using the pin diode. For ON-state and OFF-state diodes, the reflection coefficients of the RAS reflector were less than −25 dB and more than −0.8 dB around 8.3 GHz, respectively. The RAS reflector with ON-state diodes can be used as a dipole antenna reflector and has the same radiation performance as a dipole with a metal reflector, while the RAS reflector with OFF-state diodes can be used as a radar absorber for RCS reduction. Meanwhile, chessboard-like geometry RAS reflector was proposed to achieve wideband RCS reduction. The RCS reduction band covers the working band and is extended to 5-18 GHz. The results show that the reconfigurable RAS reflector can contribute to the antenna RCS reduction at working frequency without loss of radiation performance of dipole antenna. With the detection and stealth technology developing rapidly, radar cross section (RCS) reduction (1-4) has been a serious problem in military applications and has attracted significant attention recently. Since the scattering of the antennas has contributed a lot to the total RCS for low observable platforms, more and more attention has been paid to antenna scattering. Shaping, coating with radar absorbing materials (RAM) and using passive and active cancellation technology are basic methods in stealth technology (5-7). Furthermore, a number of new structures and materials are applied to the RCS reduction of antenna, such as artificial magnetic conductor (AMC), radar absorbing structure (RAS), frequency selective surface (FSS), etc. (8-11). However, these structures and materials cannot be used for stealth in the working band. When RAS is used, the gain of the antenna has a large degeneration (12), and the application of AMC will increase the profile of the antenna. All of them greatly deteriorate the stealth performance and application of radar system or other platform. In early years, antennas did not need to work in airborne or missile borne systems continuously. To realize the stealth of antenna, the radar was opened in close proximity to the target and shut down through the dangerous area. This method has the advantages of simple, feasible, and good stealth characteristic. In addition, the radiation performance of the antenna is preserved. However, this method can only reduce the antenna mode scattering, and the structural mode scattering still exists. Meanwhile, general metamaterials are completely passive structures, and the properties of these metamaterials cannot be changed. Therefore, in the complex electromagnetic environment, these metamaterials cannot be able to quickly adapt to the changes in the external electromagnetic environment and reduce its effect. In order to overcome these problems, reconfigurable RAS is put forward as a new concept. Reconfigurable technology has been successfully applied to antenna design. Early research focused on changing the current distribution by adjusting the radiator structure, which made the frequency, pattern, polarization or impedance of antenna changed. Currently, the reconfigurable metamaterial is