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.

An eight‐element multiple‐input–multiple‐output (MIMO) antenna array for ultra‐wideband (UWB) communication is reported. The proposed array contains eight antenna elements having annular ring slots in the middle of each element and tapered feed lines for impedance matching. The defected ground planes are introduced on the back of these antenna elements. Moreover, closed‐loop frequency selective surfaces are introduced to achieve enhanced isolation between antenna pairs. A quad‐strip connected circular arc decoupling structure is also used to enhance the isolation among particular antenna elements. These decoupling structures provide isolation of 20 dB over most of the desired UWB spectrum. The proposed UWB‐MIMO array has dimensions of 60 × 93 mm ² . The proposed design is suitable for integration with system‐in‐package applications and provides ease of connectivity on all four sides.