Electromagnetic interference (EMI) shielding materials, especially ones with excellent shielding effectiveness (SE), high optical transmittance, long‐term stability as well as high uniformity, are urgently desired to meet the requirements of many applications. Herein, an extremely transparent, stable and uniform silver nanowire (Ag NW)–poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite film as an EMI shielding material is prepared, which possess excellent shielding capability to both small signal and high power microwaves (HPM). The composite film exhibits SE of 30.5 dB in the frequency range of 1–12 GHz (small signal) and simultaneously has an optical transmittance of 91.0%. The SE continuously increases to 41.4 dB, while the optical transmittance still maintains at 81.1%. The composite film is very uniform, and its SE is almost unchanged even when exposed in air for a year. The SE of this composite film under the excitation of HPM is also thoroughly investigated. The HPM SE is much larger than that of small signal. As the power density of HPM is increased, the SE firstly remains unchanged, then continuously increases, and finally saturates. The SE exceeds 50 dB with the excitation power density of 40 W. More interestingly, the SE is saturated at a fixed HPM power density.

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This letter demonstrates an ultra-wideband circularly polarized cavity-backed crossed-dipole antenna. It consists of a modified crossed-dipole and a modified cavity. Each arm of the modified crossed-dipole is mainly made up by the combination of a triangle and a fan-shaped sector, and the arms within the same layer of substrate are connected by a vacant-quarter ring. The modified cavity is composed of a rectangular cavity, four coupled rotated vertical metallic plates, and four sequentially rotated metallic steps. Through combining the modified crossed-dipole and modified cavity together, ultra-wideband characteristics in terms of − 10-dB impedance bandwidth (IBW) and 3-dB axial-ratio bandwidth (ARBW) can be realized. The IBW and ARBW are correspondingly calculated to be 128.9% and 121.2%. The prototype of the proposed antenna was fabricated and measured. The proposed antenna has a compact size of 0.74 λ0 × 0.74 λ0 × 0.17 λ0 (λ0 is the wavelength at the lowest frequency of operation band). The measured IBW and ARBW are 125.2% (1.67–7.26 GHz) and 120.1% (1.79–7.17 GHz), respectively, which are in good agreement with the simulated ones. The proposed antenna has stable radiation patterns in the operation band and exhibits a right-hand circular polarization with a peak gain of 12.2 dBic at 6.7 GHz.

Shielding effectiveness (SE) dominates the shielding performance of materials. Under the excitation of high-intensity transient electromagnetic pulse, especially the wide-band transient electromagnetic pulse, how to characterize and calculate the SE of shielding materials is not clear. In order to reveal the shielding performance of materials towards the wide-band transient electromagnetic pulse, a systematic experimental investigation was performed on a home-made SE measurement system. The "peak value reduction (SE PR )" is verified to be an effective approach for the characterization of SE of shielding materials. The SE of the employed materials shows no noticeable change even with the excitation field intensity increasing to 200 kV/m, which is significantly different from that of high-power microwave (HPM). Under the excitation of HPM, the SE of materials starts to increase at a field intensity of 19.4 kV/m and becomes saturated at 33.6 kV/m. Further analysis discloses that the variation of SE of materials is mainly dependent on two factors, one is the intrinsic property of the material itself, and the other is energy density spectrum of the excitation high-intensity transient electromagnetic pulse. The energy in per frequency unit (10 MHz) for wide-band transient electromagnetic pulse is far lower than that of HPM, resulting in an evident dissimilarity in the changes of SEs of shielding materials.INDEX TERMS shielding performance, wide-band transient electromagnetic pulse, peak value reduction, energy density spectrum.

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