In this paper, a novel and miniaturized band-stop frequency selective surface (FSS) is presented. This FSS provides effective shielding in X-band, with attenuation of at least 56 dB. The proposed FSS provides 3-dB fractional bandwidth of 48% which is necessary to cover X-band. Moreover, the proposed design is polarization independent as it provides a stable frequency response at normal and oblique angles of incidences for both perpendicular TE and parallel TM wave modes. The copolarized and cross-polarized scattering parameter S ₂₁ is analyzed at the selected band-stop/notch frequencies. More importantly, the proposed FSS is suitable for conformal applications and hence finds wider employability. A prototype of the proposed FSS is fabricated and tested. The measured results are in good agreement with the simulated results.

This article reports on very efficient and highly miniaturized wideband polygon-shaped frequency selective surface (PFSS) shields for the planar and conformal applications in the X-band. These shields have been analyzed for both lossy as well as for low-loss substrates. The conformal configurations of PFSS are particularly investigated for inward, outward, and double-curved profiles useful for a variety of applications. The conformal designs have been tested for two different radii of curvatures. The models have been simulated using a hybrid simulation approach for electrically large geometries. The equivalent circuit model as well as the analytical model are determined. The proposed PFSS designs offer stable angular response up to 60° for planar and all conformal geometries on both lossy and low-loss prototypes. Shielding effectiveness of at least 55 dB and 48 dB has been measured for flat/nonconformal and conformal configurations, respectively.

This research work proposes a compact four-port multiple-input multiple-output (MIMO) antenna that operates in the whole license free ultra-wideband (UWB) spectrum of 3.1–10.6 GHz. Spatial diversity has been introduced by arranging these antennas in close proximity without developing a strong mutual coupling. Antenna elements are evolved from a conventional rectangular patch antenna whereas a customized decoupling structure is introduced on the back side of the substrate to achieve the desired isolation level. The parasitic decoupling structure consists of different features which are resonant at different frequencies offering a whole UWB coverage. In addition to the decoupling structure a dumbbell shaped stub has also been introduced to the partial ground plane to suppress the mutual coupling. The overall measured isolation among elements is more than 20 dB. Different MIMO performance parameters have also been investigated from the measured results. Whole MIMO system measures 0.41 λ_o × 0.44 λ_o at 3.1 GHz. The MIMO system is intended for high data rate and short-range communication devices used in wireless personal area networks.

In this letter, a low-profile, miniaturized four-element ultrawideband (UWB) antenna for four-port multiple-input- multiple-output (MIMO) configuration is proposed. The MIMO antenna elements are organized in a cuboidal geometry around a polystyrene block. An inverted L-shaped structure provides decoupling among the antenna elements. This structure is frequency-selective-surface-based and has slotted V-shapes etched in it. In addition to that, a square spiral parasitic structure improves input impedance matching over the desired frequency band. Antenna elements are realized on low-profile FR-4 substrate having compact dimensions of 32 × 36 × 1.5mm ³ . The proposed three-dimensional (3-D) UWB-MIMO system achieves good impedance matching and an effective isolation of 20 dB among antenna elements in most of the band. The reported configuration is suitable for nonplanar/3-D system-in-package applications where a planar arrangement of four elements is not possible due to size limitations.

This study presents a two element multiple‐input‐multiple‐output (MIMO) reconfigurable antenna for ultra wideband (UWB) applications. Each individual antenna is composed of a modified square radiating patch. The array can be reconfigured by either placing antenna elements orthogonally for corner installation or by placing them back‐to‐back for compact three‐dimensional (3D) modules. The design is fabricated on FR4 substrate having dimensions 40 mm × 37.5 mm × 1.5 mm. Port isolation greater than 20 dB in the complete band is achieved by introducing an efficient decoupling structure in the ground plane. Performance parameters such as S‐parameters, radiation patterns, envelope correlation coefficient, total active reflection coefficient and channel capacity loss indicate that the proposed MIMO design is a suitable candidate for high data rate UWB applications. The proposed solution is suitable for non‐planar designs around wall corners or for compact 3D structures where side‐by‐side placement is not practical due to size constraints.