In this letter, an ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna using a novel fence-type decoupling structure, which has high isolation in the UWB, is presented. The MIMO design consists of two half-cutting UWB antenna units that have good low-frequency impedance-matching performance because of the use of a rectangular slot on the radiation patch. Meanwhile, the isolation in the operating band is enhanced by introducing the fence-type decoupling structure at the ground of the antenna. Furthermore, the L-shaped parasitic branches are designed to heighten the impedance bandwidth and isolation in the low-frequency band, i.e., 3-3.4 GHz. The simulation and experiments show that the antenna has low mutual coupling (S21 <; -25 dB) and a low envelope correlation coefficient (ECC <; 0.004) in the UWB.

A small ultrawideband (UWB) slot antenna is proposed using a stepped impedance resonator feeding line, aiming at improving band-edge selectivity. The proposed antenna mainly comprises a feeding line with low-pass characteristics at the top of the dielectric substrate and two slots at the bottom. The stepped impedance resonator is used to improve the upper band-edge selectivity, and the narrow slot near the stepped slot improves the lower band-edge selectivity. The frequency selection range, the frequency selective characteristic, and the reflected zeros of the antenna upper band-edge are analyzed and studied. The measured results show that the antenna covers the frequency range of UWB systems from 3.1 to 11 GHz (114%) with the reflection coefficient less than -10 dB. Compared with the traditional UWB antenna, the proposed compact antenna has advantages in size and band-edge selectivity and is more suitable for UWB applications. The ratio of the -3 dB bandwidth to the -10 dB bandwidth is 1.038, which is very close to 1.

A stochastic finite-difference time domain (S-FDTD) combined with the piecewise linear recursive convolution method is applied to model wave propagation in unmagnetized plasma with random plasma frequency. The stretched-coordinate perfectly matched layer implementation of the S-FDTD method is also presented. The accuracy and efficiency of the proposed algorithm are validated by numerical examples.

In this work, we propose novel layer-structured polymer composites (PCs) for manipulating the electromagnetic (EM) wave transport, which holds unique electromagnetic interference (EMI) shielding features. The as-prepared PCs with a multilayered structure exhibits significant improvement in overall EMI shielding effectiveness (EMI SE) by adjusting the contents and distribution of electrical and magnetic loss fillers. The layer-structured PCs with low nanofiller content (5 wt % graphene nanosheets (GNSs) and 15 wt % Fe₃O₄) and a thickness of only 2 mm exhibited ultrahigh electrical conductivity and excellent EMI SE, reaching up to 2000 S/m and 45.7 dB in the X-band, respectively. The increased EMI SE of the layer-structured PCs was mainly based on the improved absorption rather than the reflection of electromagnetic waves, which was attributed to the “absorb-reflect-reabsorb” process for the incident electromagnetic waves. This work may provide a simple and effective approach to achieve new EMI shielding materials, especially for absorption-dominated EMI shielding.

In this letter, a miniaturized spoof surface plasmon polaritons (SSPPs) low-pass filter with a novel transition structure is proposed. The novel transition structure is designed by two rectangular strips with an inclination of 17° and right-angled triangle patches. In this work, we analyzed the normal and azimuthal components of the electric field perpendicular to the plane of the filter at different locations, verifying the effectiveness of the transitional structure. Besides, efficient conversion between quasi-transverse electromagnetic (TEM) waves and transverse magnetic (TM) polarized SSPPs waves are achieved by loading the novel transition structures. The designed filter can suppress unnecessary radiation loss and increase transmission efficiency. More importantly, the filter size is 47.52 mm × 7.47 mm, and its length is reduced by at least 61 % compared with other low-pass filters with the same cut-off frequency. This work has promoted the development and application of SSPPs low-pass filter and related equipment in microwave frequencies.