Integrative Transmitarray with Gain-Filtering and Low-Scattering Characteristics

This paper presents a design concept of integrative transmitarray antenna (TAA) with gain-filtering and low-scattering characteristics. The integrative TAA element combines a bandpass frequency-selective surface (FSS) element and a square dielectric post with antireflection pyramidal structures (SDPP), achieving the simultaneous control of in-band transmitted waves and out-of-band reflected waves. The FSS element provides the phase-shifting and gain-filtering capabilities around the center operating frequency f₀. Meanwhile, the SDPP elements with different heights are utilized to reduce the scattering cross section (SCS) based on the phase cancellation principle. To realize wideband and wide-angle SCS reductions, also to mitigate the in-band radiation degradation, the optimal SDPP arrangement is determined with subarray segmentation. In the experiment, a 42 × 42-element integrative TAA is designed. Against only the FSS TAA, the simulated results show that loading the optimal SDPP array can realize the scattering reduction in a 10:1 bandwidth up to 60°, including ~5 dB/~10 dB SCS reductions in 0.5-1.5 f₀/1.5-5 f₀, respectively. Moreover, the integrative TAA achieves gain-filtering responses with out-of-band suppression levels higher than 20 dB. After fabricating the FSS TAA and the SDPP array by the technologies of standard PCB fabrication and 3-dimensional printing, respectively, the proposed design is further demonstrated by experiments.