In this study, the novel electronically switchable broadband metamaterial absorber, using a PIN diode, is proposed. The unit cell of the absorber was designed with a Jerusalem-cross resonator and an additive ring structure, based on the FR-4 dielectric substrate. Chip resistors and PIN diodes were used to provide both a broadband characteristic and a switching capability. To satisfy the polarization insensitivity, the unit cell was designed as a symmetrical structure, including the DC bias network, electronic devices, and conductor patterns. The performance of the proposed absorber was verified using full-wave simulation and measurements. When the PIN diode was in the ON state, the proposed absorber had a 90% absorption bandwidth from 8.45–9.3 GHz. Moreover, when the PIN diode was in the OFF state, the 90% absorption bandwidth was 9.2–10.45 GHz. Therefore, the absorption band was successfully switched between the low-frequency band and the high-frequency band as the PIN diode was switched between the ON and OFF states. Furthermore, the unit cell of the proposed absorber was designed as a symmetrical structure, and its performance showed insensitivity with respect to the polarization angle.
Metasurfaces can provide novel functionality for absorbing electromagnetic waves through a periodic array of inductive/capacitive resonators by controlling the material's permittivity and permeability. This attractive characteristic makes them widely applicable to various electromagnetic applications. However, conventional metasurfaces are dispersive and suffer from a narrow bandwidth with uncontrollable and unchangeable functions because the effective permittivity and permeability are tailored to a certain resonance frequency. Therefore, many studies have focused on how to increase the absorption frequency bandwidth and control the absorption frequency by using reconfigurable metasurfaces. This paper presents a report on the most recent progress in the realization of reconfigurable metasurfaces based on advanced materials for frequency‐selective absorption in the microwave, millimeter‐wave, sub‐terahertz, terahertz, and visible ranges. Furthermore, their tuning ratios for different advanced materials and spectra are summarized and compared. This progress report provides guidelines for the material selection for and the design of reconfigurable metasurfaces.
This study focused on the radome and proposed an absorber with a meta-dome structure for ultra-wideband radar absorption using an FR-4 dielectric material on the metasurface absorber for protection. In addition to protecting the absorber, the metasurface absorber exhibited ultra-wideband frequency absorptivity from radar signals, with an absorptivity band from 4.6–12 GHz, including the C and X frequency bands of radar signals. A wide incidence angle should also be considered in addition to the absorption frequency band. Experimental results were obtained for all polarization angles at normal incidence for 5–14 GHz. Sensitivity to incident angle from 0° to 40° in the transverse electric mode and 0° to 60° in the transverse magnetic mode were observed. The proposed concept was demonstrated using full-wave simulation and experimental measurements.
In this paper, we propose a stretchable radio-frequency (RF) strain sensor fabricated with screen printing technology. The RF sensor is designed using a half-wavelength patch that resonates at 3.7 GHz. The resonant frequency is determined by the length of the patch, and it therefore changes when the patch is stretched. Polydimethylsiloxane (PDMS) is used to create the substrate, because of its stretchable and screen-printable surface. In addition, Dupont PE872 (Dupont, NC, American) silver conductive ink is used to create the stretchable conductive patterns. The sensor performance is demonstrated both with full-wave simulations and with measurements carried out on a fabricated sample. When the length of the patch sensor is increased by a 7.8% stretch, the resonant frequency decreases from 3.7 GHz to 3.43 GHz, evidencing a sensitivity of 3.43 × 107 Hz/%. Stretching the patch along its width does not change the resonant frequency.
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