A four-element compact wide-band optically transparent MIMO antenna with a full ground plane is proposed. The four elements transparent MIMO system has a compact size of $24\times 20$ mm ² with the undivided ground plane as most of the real-time systems demand a common reference. The complete antenna system achieves around 85% transparency due to a combination of AgHT-8 and Plexiglas which forms the transparent conductive patch/ground and substrate, respectively. The antenna geometry leads dual-band operation ranging from 24.10 - 27.18 GHz (Impedance bandwidth = 12%) and 33 - 44.13 GHz (Impedance bandwidth $=28.86$ %) targeting the mm-wave 5G applications. The 4-element antenna system achieves isolation between inter-elements >16 dB and maximum gain value of greater than 3 dBi with more than 75% efficiency. The proposed transparent MIMO antenna is evaluated in terms of diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and mean effective gain (MEG) where decent MIMO performance with isolation more than >16 dB between the adjacent and other elements is achieved. Transparent MIMO antenna achieves directional patterns for the operating band with the value of DG >9, ECC < 0.1, TARC value less than −15dB, and the ratio of MEG within the agreed limit of ±3 dB confirming acceptable MIMO/diversity performance.

A four-port dielectric resonator-based connected ground multiple-input multiple-output (MIMO) antenna is designed. The presented antenna was excited through the aperture feeding technique. The dual bands are achieved by optimally feeding the rectangular dielectric resonator through engineered triangular slots. The antenna has operating modes of and at 4.5 GHz and 5 GHz, respectively. It presents a 2 : 1 VSWR bandwidth of 2.64% (4.48 GHz–4.60 GHz) and 1.2% (4.96 GHz–5.04 GHz) in the lower and upper bands, respectively. The edge-to-edge distance between array elements is around 7.5 mm. The single antenna dimension is 30 mm × 30 mm, whereas the four-port antenna dimension is 60 mm × 60 mm. The optimum isolation was achieved by carefully placing the antenna elements on the substrate through multiple iterations. The antenna provides port isolation better than 20 dB at both resonances with full ground profile. The advantage of the antenna is that it provides fair antenna and MIMO parameters without additional isolation techniques. The antenna has efficiency in order of 88.02% and 86.31%. The peak gain is 7.67 dBi and 8.32 dBi at 4.5 GHz and 5 GHz, respectively. The optimum envelope correlation coefficient (ECC) is 0.037, channel capacity coss (CCL) is 0.2 bits/sec/Hz, diversity gain (DG) is 9.99 dB, and total active reflection coefficient (TARC) is −18.87. The antenna elements are orthogonally placed with adequate separation to achieve polarization diversity and spatial diversity. The antenna provides the utilization in Sub-6 GHz 5G and WLAN communication applications.

An engineered novel tunable dual-band metamaterial antenna based on stacked split ring resonator (SRR) array is presented. The μ-negative SRR array present at two sublayers of stacked microstrip patch antenna substrate adds tuning capability to the antenna with marginal trade-off between antenna gain and cross-polarization. If the size of resonator element is considerably smaller than resonance wavelength, ideally lesser than λ/10, the resonator would support the resonating mode of antenna. Compact SRR array embedded in radiator facilitate the antenna tuning to intended allocated spectrum of L5- and S-band frequencies without modifying external dimensions of patch antenna, which in turn helps the satellite payload design. The variations in SRR array dimensions and inter-element spacing are subsequently utilized to maintain the antenna gain and voltage-standing wave ratio. The proposed design of inset fed antenna, matched at 50 Ω, was validated by experimental results and it is suitable for global positioning satellite applications.