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In this paper, a miniaturized frequency-selective rasorber (FSR) with an ultra-wide transmission band (| S21 | <1 dB) is presented. The FSR is made up of a lossless multi-layer cascaded frequency-selective surface (FSS) with a 2.5-D lossy layer above, separated by an air gap. Modified metallic Jerusalem crosses loaded with lumped resistors serve as the unit cell of the lossy layer. An equivalent parallel LC circuit with high inductance and extremely low parasitic capacitance is introduced by zigzag strips and vias, which broaden the transmission band significantly. The equivalent circuit model (ECM) is constructed to provide further insight into the structure. Simulation results show that the proposed FSR exhibits an ultra-wide transmission band of 1-dB from 6.20 to 17.97 GHz (97.4%) with a minimum insertion loss of 0.074 dB. Meanwhile, an 80% absorption band covering 2.58-4.13 GHz is achieved below the passband. For demonstration, an experimental prototype of the 2.5-D FSR is fabricated and measured, and the simulated and measured results are reasonably consistent.

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In this paper, a dual-polarized planar ultra-wideband modular antenna (PUMA) with wide-scanning angle matching layers is proposed. The multiple dielectric layers and frequency selective surfaces (FSS) are loaded on the dipoles. Each frequency selective surface is etched on the dielectric plate as one wide-angle -matching layer. By applying three wide-angle-matching layers, the wide-scanning angle performance is guaranteed. As for the ultra-wideband performance, a metal cylinder is added to the lower space between adjacent dipoles, and the upper end of the cylinder has a certain distance from the dipole. This forms a “ridge” structure which shift problematic common-mode resonances caused by circulating current out of band. A dual-polarized 256-port array (16×16) is set and simulated. The simulation result indicates that the proposed antenna operating over 4.79GHz -20.15GHz (4.20:1) achieves VSWR<3 while scanning to 60° in E-plane and D-plane, and to 45° in H-plane respectively.

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Ultrawideband phased antenna array has been widely used in communications, radars and detection. However, the high profile and poor wide-angle scanning characteristics have always been the critical limitation for many available ultrawideband antenna applications. In this paper, an ultra-thin loading window (UTLW) is proposed to replace the wide-angle impedance matching (WAIM) superstrate in the planar ultrawideband modular antenna arrays (PUMA), and reduces the profile height greatly. The UTLW consists of two strips in parallel, and each strip is loaded with two resistors and one capacitor. Following the equivalent circuit model (ECM) of the PUMA, the resistance and capacitance are specially designed to make the complex impedance of the UTLW equal to the impedance introduced by the WAIM. A dual-polarized PUMA with an UTLW achieves 6-18 GHz impedance bandwidth with active VSWR≤2.6 for scanning up to 60 • and active VSWR≤3 for scanning up to 70 • in E/D/H plane. The profile height of the proposed PUMA is only less than 0.07λ l , or, 0.24λ h with reference to the typical Nyquist half-wavelength spacing frequency. A 20×20 prototype PUMA with the UTLW was fabricated and its measured results were found consistent with the simulation results.INDEX TERMS Planar ultrawideband modular antenna (PUMA), ultra-thin loading window (UTLW), low-profile, wide-angle scanning