Design of A Single Antenna With Tunable In-Band RCS Null Through Load Impedance Control

Abstract: Reducing the in-band radar cross section (RCS) of antennas has been a widely concerned problem. However, most of works focus on RCS reduction of antenna arrays, or need to additionally increase the size of a single antenna. Therefore, this work presents a method to control the null of the in-band RCS by changing the load impedance of the antenna without additional aperture. Then, the monostatic and bistatic RCS can be effectively reduced. First, the relationship between the null position and the load impedance is calculated by analyzing the in-band scattering field of the antenna. Second, the performance of RCS null control is verified by the traditional patch antenna, whose operating frequency is designed at 2 GHz. The load impedance of the antenna is controlled by cascading an open circuit stub of different lengths on the feeding line. Simulated results show that the proposed method can tune the null of in-band RCS from 0o to 60o under linear polarized normally incident plane wave. By setting the null reasonably, it can achieve 10 dB reduction for both monostatic and bistatic RCS at the same time. Moreover, the radiation performance of the antenna basically remains unchanged, and the gain is greater than 6.5 dBi. Measured results verify the effectiveness of the design method.