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This study reports on a highly miniaturised polarisation selective surface (PSS) for dual-band Wi-Fi and WLAN applications. The proposed unit cell consists of two independently tuneable square loops. The outer loop is split with a gap of 0.2 mm to introduce polarisation selectivity and miniaturisation for lower-frequency band of 2.5 GHz. The inner square loop is inductively loaded with arms to suppress 5.45 GHz frequency band. These configurations have resulted in a unit element size of λ ∘ / 14 at 2.5 GHz, which is not presented before to the best of the authors' knowledge. A wide rejection bandwidth ( − 10 dB ) of more than 600 and 1180 MHz is obtained around 2.5 and 5.45 GHz, respectively. Furthermore, the proposed PSS exhibits an excellent polarisation selective characteristic by generating two stopbands at 2.5 and 5.45 GHz when illuminated by horizontal (TM) incident waves, whereas vertically (TE) polarised incident waves result in the generation of passbands for these two frequencies. Numerical validation through equivalent circuit modelling of the proposed PSS has also been carried out. A finite prototype containing 31 × 33 elements is fabricated and tested. The measured results demonstrated that the PSS has excellent potential for applications that employ polarisation separators and wave generators.

Conformal antennas placed on complex surfaces are receiving more attention as a method to increase the coverage of modern wireless communication systems. Furthermore, frequency reconfigurable antennas are being used in the development of multi-band multi-radio wireless platforms to simplify designs. In this study, theoretical development and a new 1 × 4 frequency reconfigurable self-adapting conformal antenna array that can be attached to changing conformal surfaces is presented. This conformal array consists of four reconfigurable microstrip patch antenna elements, a reconfigurable sensor circuit used to measure the curvature of the conformal surface and voltage controlled phase shifters. These phase shifters are controlled by the reconfigurable sensing circuit to implement phase-compensation to autonomously recover the pattern in both bands of the reconfigurable 1 × 4 array as the wedge- and cylindrical-shaped surface on which the array is attached upon change in shape. Throughout this study, analytical computations, simulations and measurements are compared and shown to agree.

A new compact multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna array is presented. The antenna array initially consisted of two monopoles placed side by side at a distance of 4 mm. A strong mutual coupling was observed so the design was modified by rotating the second radiator at 90° at a distance of 1 mm. Wideband isolation is achieved by exploiting polarisation diversity of antenna elements. Simulation in HFSS and printed prototype results validate the high isolation, over 21 dB on the entire 2.5–12 GHz frequency range. A prototype was fabricated on a low loss substrate of Rogers TMM4 measuring 23 × 39.8 mm2. To evaluate the diversity performance, the envelope correlation coefficient was calculated resulting below −20 dB, thus ensuring good diversity performance. The compactness of the proposed UWB-MIMO design is finally compared against alternative solutions already present in the literature.

A compact planar UWB-MIMO antenna array with WLAN band rejection is presented. The array consists of four monopole radiators and a common ground plane. These monopoles are placed in such a way that the polarisation diversity of nearly placed radiators is exploited, resulting in high isolation. The proposed MIMO antenna array is electrically small (50 × 39.8 mm2), printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. A band-stop design was inserted on the ground plane to behave similar to a LC band-stop filter and reject the WLAN band. Simulation and measurement results satisfy the return loss requirement of better than 10 dB and isolation better than 17 dB over the entire 2.7–5.1 and 5.9–12 GHz bandwidths.

An ultra-compact planar antenna aiming to be part of an imaging antenna array operating in the broad 3–18 GHz frequency range is presented. The antenna is made of two closely packed wide-band monopoles for simultaneous transmission and reception functionalities. A high isolation ( >20 dB) between the two patches is achieved through the insertion of a structured ground plane (decoupling structure). A prototype was fabricated on a Roger R4003c laminate measuring 58 × 33 mm2 and used in inverse synthetic array radar configuration for detecting a steel object with sub-centimetre spatial resolution.

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.