On the Design of Multiband Antenna Employing AFSR Structure as Ground Plane for Low Out-of-Band RCS

Two design parameters of a multiband antenna with low radar cross-section (RCS) are studied in this paper. A dual-band absorptive frequency-selective reflection (AFSR) structure is utilized as the ground plane for a dual-band antenna to achieve low out-of-band RCS. The first parameter is the separation between the bandstop frequency-selective structure (FSS) and the absorber. Even-odd mode analysis is utilized to investigate the physical mechanism of the absorption occurring at the lower reflection band. Flat reflection band, which is important to maintain the radiation characteristics of the antenna, is realized based on this analysis. The second design parameter is the size of the metal ground plane of the dual-band stacked patch antenna with the AFSR ground. The lower limit is bounded by achieving good antenna impedance matching at the low-frequency band while the upper limit is characterized by the RCS reduction performance.