Low RCS Antennas Based on Dispersion Engineering of Spoof Surface Plasmon Polaritons

In this paper, we propose the design of antennas with low radar cross section (RCS) based on dispersion engineering of spoof surface plasmon polaritons (SSPPs). The antenna consists of a feeding monopole and SSPPs guiding structure placed vertically on a metal ground. By comprehensively engineering the weak and strong dispersion regimes of the SSPPs structure, the cutoff frequency of SSPPs can be made close to the upper operating frequency of the feeding monopole. In this way, the SSPPs structure serves as a high-efficiency radiator in the operating band and as a broadband absorber out of band, leading to low RCS out of band. As an example, a C-band antenna with low RCS in the X-band was designed, simulated, and measured. Both the simulation and experiment results show that the antenna can radiate in the C-band, with average gain 6 dB and fractional bandwidth 28%. In order to evaluate the RCS reduction performances, a 5× 5 antenna array was fabricated and the mono-static RCS was measured. The measured results show that the mono-static RCS is reduced by more than 10 dB in the whole X-band (8.0-12.5 GHz), with a maximal reduction above 30 dB. The design method provides an effective alternative to low-RCS antennas.