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This work proposes a frequency selective metasurface (FSM) with two transmission windows within the wideband radar cross section (RCS) reduction band. First, to achieve dual transmission windows, dual-band and triple-band artificial magnetic conductors are introduced as the two elements of the FSM. Second, the input reactance conditions of the two elements under the reduction condition are derived, and the circuit parameters are optimized to meet these conditions. Furthermore, the transmission and RCS reduction performance after arraying are analyzed based on array theory. Third, based on the corresponding equivalent circuit models, two dual-layer structural elements are designed and arranged in a checkerboard pattern. Finally, a metasurface prototype is fabricated and experimented with. The experimental results demonstrate that the proposed FSM exhibits a −10 dB RCS reduction from 4.2 GHz to 13.9 GHz and transmission windows with insertion losses of −1.45 dB at 7.3 GHz and −1.52 dB at 12.6 GHz.

High-temperature ablation leads to variations in the thickness of the radome during high-speed reentry, consequently impacting the overall performance of the antenna-radome system. This article develops models of laminar ablation shapes for a typical sphere-cone radome on reentry vehicles caused by laminar ablation during reentry. The main electromagnetic (EM) performance of the radome under different ablation states, including boresight error (BSE) and transmission loss (TL), was calculated using the time-domain finite integration method. The findings indicated that ablation causes significant variations in EM performance. Specifically, BSE exhibits significant fluctuations due to changes in the ablation thickness of the spherical nose, while TL experiences a sharp increase with a higher thickness of conical part ablation. We have redefined the asymmetry of insertion phase delay (IPD), taking into account the influence of the antenna and offering more comprehensive insights on the cause of BSE by conducting analysis on the IPD distribution. This work contributes to the prediction of the EM performance of radomes with laminar ablation during reentry and provides guidance for subsequent compensation measures.

This article presents an ultrawideband dual-bandpass frequency-selective surface (FSS) that exhibits outstanding transmission characteristics and a miniaturization feature in the required frequency band. In order to obtain a dual-band filtering response, initially, a specific topological structure of a dual-band bandpass microwave filter is theoretically investigated, and using periodic structures with capacitive, inductive, or resonant-type surface impedances synthesizes its components. Subsequently, employing a compact cascaded hybrid resonant element to construct the FSS, which is composed of convoluted strip grids (CSGs), convoluted square rings (CSRs), and square rings arranged on different layers. In addition, an accurate equivalent circuit model (ECM) is constructed to analyze the working mechanism of the proposed FSS. Finally, the designed FSS is made and measured. The results indicate that the designed FSS achieved −3-dB bandwidths of 105.4% from 1.01 to 3.26 GHz and 47.8% from 3.75 to 6.10 GHz, respectively. At the center frequency of the first passband, the FSS’s size is as compact as $0.056\lambda _{0} \times 0.056\lambda _{0}$ . The test results obtained are in good agreement with the results of the full-wave simulation and show excellent resonant stability with respect to different polarizations and incident angles up to 45°.