Open Access
Multi antenna structure assisted by metasurface concept providing circular polarization for 5G millimeter wave applications
(Nature, 2025-05-21) Althuwayb, Ayman Abdulhadi; Ali, Esraa Mousa; Alibakhshikenari, Mohammad; Virdee, Bal S.; Rashid, Nasr; Kaaniche, Khaled; Atitallah, Ahmed Ben; Elhamrawy, Osama I.; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
This paper presents a circularly polarized multi-antenna structure designed for 5G millimeter-wave applications. The structure is based on circular patch radiators, each enhanced with metasurface (MTS) characteristics through the integration of multi-split ring slots. Each radiating element is enclosed within a decoupling wall constructed from a microstrip transmission line, which features both wide (capacitive) and thin (inductive) impedance profiles. The antennas are excited from below using metallic pins, which connect to the radiators through via-holes stemming from coplanar waveguide ports on the ground plane. Experimental results demonstrate a wide bandwidth from 25.6 to 29.7 GHz, corresponding to a fractional bandwidth of 14.82%. Additionally, the antenna exhibits stable radiation patterns, with an average gain of 2.7 dBi and a radiation efficiency of 57%. Using a single radiator configuration, a 3 × 3 antenna array was implemented. In this design, electromagnetic coupling between adjacent radiators is significantly reduced. The resulting array, measuring 20 × 20 × 0.32 mm3, achieves excellent performance across a wide frequency range from 24 to 31 GHz, corresponding to a bandwidth of 25.45%. Key metrics include an average isolation between radiating elements exceeding 17 dB and an average gain and radiation efficiency of 9.0 dBi and 91.5%, respectively.
Open Access
Virtual antenna array for reduced energy per bit transmission at Sub-5 GHz mobile wireless communication systems
(Elsevier, 2023) Alibakhshikenari, Mohammad; Virdee, Bal S.; Mariyanayagam, Dion; García Zuazola, Ignacio Julio; Benetatos, Harry; Althuwayb, Ayman Abdulhadi; Alali, Bader; Xu, Kai-Da; Falcone Lanas, Francisco; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This paper presents an innovative technique to synthesize a virtual antenna array (VAA) that consumes less energy than conventional antenna arrays that are used in mobile communications systems. We have shown that for a specific spectral efficiency a wireless system using the proposed virtual antenna array consumes significantly less energy per bit (∼3 dB) than a wireless system using a conventional multiple-input multiple-output (MIMO) array. This means the adoption of the proposed VAA technology in smartphones, iPad, Tablets and even base-stations should significantly reduce the carbon footprint of wireless systems. The proposed VAA is realized by employing a pair of linear antenna arrays that are placed in an orthogonal configuration relative to each other. This orthogonal arrangement ensures the radiation is circularly polarized. The size of the standard radiating elements constituting the VAA were miniaturized using the topology optimization method. The design of the VAA incorporates substrate integrated waveguide (SIW) and metasurface technologies. The function of SIW in the design was twofold, namely, to reduce energy loss in the substrate on which the VAA is implemented, and secondly to mitigate unwanted electromagnetic interactions between the neighboring radiating elements and thereby enhancing isolation which otherwise would degrade the radiation characteristics of the array. Metasurface technology served to effectively increase the effective aperture of the array with no impact on the footprint of the array. The consequence of SIW and metasurface technologies was improvement in the gain and radiation efficiency of the array. The proposed four orthogonal 4-element VAA covers the entire sub-5 GHz frequency range, and it radiates bidirectional in the azimuth plane and omni-directional in the elevation plane. Moreover, it is relatively easy to design and fabricate. The proposed VAA has dimensions of 0.96λ0 × 0.96λ0 × 0.0016λ0 at mid-band frequency of 3 GHz. VAA has a measured gain of 25 dBi and radiates with 90% efficiency. The average isolation between the linear arrays constituting the virtual array is better than 27 dB.
Open Access
A comprehensive survey on "Various decoupling mechanisms with focus on metamaterial and metasurface principles applicable to SAR and MIMO antenna systems"
(IEEE, 2020) Alibakhshikenari, Mohammad; Babaeian, Fatemeh; Virdee, Bal S.; Aïssa, Sonia; Azpilicueta Fernández de las Heras, Leyre; See, Chan H.; Falcone Lanas, Francisco; Althuwayb, Ayman Abdulhadi; Huynen, Isabelle; Abd-Alhameed, Raed; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Nowadays synthetic aperture radar (SAR) and multiple-input-multiple-output (MIMO) antenna systems with the capability to radiate waves in more than one pattern and polarization are playing a key role in modern telecommunication and radar systems. This is possible with the use of antenna arrays as they offer advantages of high gain and beamforming capability, which can be utilized for controlling radiation pattern for electromagnetic (EM) interference immunity in wireless systems. However, with the growing demand for compact array antennas, the physical footprint of the arrays needs to be smaller and the consequent of this is severe degradation in the performance of the array resulting from strong mutual-coupling and crosstalk effects between adjacent radiating elements. This review presents a detailed systematic and theoretical study of various mutual-coupling suppression (decoupling) techniques with a strong focus on metamaterial (MTM) and metasurface (MTS) approaches. While the performance of systems employing antenna arrays can be enhanced by calibrating out the interferences digitally, however it is more ef cient to apply decoupling techniques at the antenna itself. Previously various simple and cost-effective approaches have been demonstrated to effectively suppress unwanted mutual-coupling in arrays. Such techniques include the use of defected ground structure (DGS), parasitic or slot element, dielectric resonator antenna (DRA), complementary split-ring resonators (CSRR), decoupling networks, P.I.N or varactor diodes, electromagnetic bandgap (EBG) structures, etc. In this review, it is shown that the mutual-coupling reduction methods inspired by MTM and MTS concepts can provide a higher level of isolation between neighbouring radiating elements using easily realizable and cost-effective decoupling con gurations that have negligible consequence on the array's characteristics such as bandwidth, gain and radiation ef ciency, and physical footprint.
Open Access
Broadband 3-D shared aperture high isolation nine-element antenna array for on-demand millimeter-wave 5G applications
(Elsevier, 2022) Alibakhshikenari, Mohammad; Virdee, Bal S.; Vadalà, Valeria; Dalarsson, Mariana; Cos Gómez, María Elena de; Alharbi, Abdullah G.; Burokur, Shah Nawaz; Aïssa, Sonia; Dayoub, Iyad; Falcone Lanas, Francisco; Limiti, Ernesto; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
The paper presents the results of a novel 3-D shared aperture 3 × 3 matrix antenna-array for 26 GHz band 5 G wireless networks. Radiation elements constituting the array are hexagonal-shaped patches that are elevated above the common dielectric substrate by 3.35 mm and excited through a metallic rod of 0.4 mm diameter. The rod protrudes through the substrate of 0.8 mm thickness. It is shown that by isolating each radiating element in the array with a wall suppresses unwanted electromagnetic (EM) wave interactions, resulting in improvement in the antenna’s impedance matching and radiation characteristics. Moreover, the results show that by embedding hexagonalshaped slots in the patches improve the antenna’s gain and radiation efficiency performance. The subwavelength length slots in the patches essentially transform the radiating elements to exhibit metasurface characteristics when the array is illuminated by EM-waves. The proposed array structure has an average gain and radiation efficiency of 20 dBi and 93%, respectively, across 24.0–28.4 GHz. The isolation between its radiation elements is greater than 22 dB. Compared to the unslotted array the improvement in isolation between radiating elements is greater than 11dB, and the gain and efficiency are better than 10.5 dBi, and 25%, respectively. The compact array has a fractional bandwidth of 16% and a form factor of 20 × 20 × 3.35 mm3.

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