This paper reports on an effective mutual coupling suppression technique in which a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array. Modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects. A detailed analysis of this proposed scheme is carried out on a low as well as on a high-permittivity substrate. Coupling suppression of 27 and 11 dB is achieved experimentally on the low- and high-permittivity substrates, respectively, with an element separation of λ _o /8. The design is compact and easy to realize and it removes drawback of poor front-to-back ratio previously reported in other decoupling techniques. In addition to high-coupling suppression, the decoupling slab can be added or removed in real time which makes this technique versatile for various applications having stringent performance requirements.

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.

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.

Presented are two different frequency reconfigurable ultra‐wideband multiple‐input multiple‐output (MIMO) antenna array designs capable of rejecting on‐demand all WLAN communications in the 4.8 to 6.2 GHz range. Both arrays consist of two monopole UWB radiators placed orthogonally with respect to each other to introduce polarisation diversity and a quarter‐wave stub connected to the ground plane via pin diodes is used to introduce the on‐demand band rejection feature. One array design has separate ground planes and the other has two ground planes connected with a printed conductor (i.e. shared). For both cases, an isolation better than 20 dB between the elements is achieved in the 2 to 12 GHz frequency range with simulations and a manufactured prototype.