We present a 4-port Multiple-Input-Multiple-Output (MIMO) antenna array operating in the mm-wave band for 5G applications. An identical two-element array excited by the feed network based on a T-junction power combiner/divider is introduced in the reported paper. The array elements are rectangular-shaped slotted patch antennas, while the ground plane is made defected with rectangular, circular, and a zigzag-shaped slotted structure to enhance the radiation characteristics of the antenna. To validate the performance, the MIMO structure is fabricated and measured. The simulated and measured results are in good coherence. The proposed structure can operate in a 25.5–29.6 GHz frequency band supporting the impending mm-wave 5G applications. Moreover, the peak gain attained for the operating frequency band is 8.3 dBi. Additionally, to obtain high isolation between antenna elements, the polarization diversity is employed between the adjacent radiators, resulting in a low Envelope Correlation Coefficient (ECC). Other MIMO performance metrics such as the Channel Capacity Loss (CCL), Mean Effective Gain (MEG), and Diversity gain (DG) of the proposed structure are analyzed, and the results indicate the suitability of the design as a potential contender for imminent mm-wave 5G MIMO applications.

This paper presents a metasurface-based single-layer low-profile circularly polarized (CP) antenna with the wideband operation and its multiple-input multiple-output (MIMO) configuration for fifth-generation (5G) communication systems. The antenna consists of a truncated corner patch and a metasurface (MS) of a $2\times2$ periodic square metallic plates. The distinguishing feature of this design is that all the radiating elements (radiator and MS) are printed on the single-layer of the dielectric substrate, which ensures the low-profile and low-cost features of the antenna while maintaining high gain and wideband characteristics. The wideband CP radiations are realized by exploiting surface-waves along the MS and its radiation mechanism is explained in detail. The single-layer antenna geometry has an overall compact size of $1.0\lambda _{0} \times 1.0\lambda _{0} \times 0.04\lambda _{0}$ . Simulated and measured results show that the single-layer metasurface antenna has a wide 10 dB impedance bandwidth of 23.4 % (24.5 – 31 GHz) (23.4 %) and overlapping 3-dB axial ratio bandwidth of 16.8 % (25 – 29.6 GHz). The antenna also offers stable radiation patterns with a high radiation efficiency (>95%) and a flat gain of 11 dBic. Moreover, a 4-port ( $2\times2$ ) MIMO antenna is designed using the proposed design by placing each element perpendicular to each other. Without a dedicated decoupling structure, the MIMO antenna shows an excellent diversity performance in terms of isolation between antenna elements, envelope correlation coefficient, and channel capacity loss. Most importantly, the operational bandwidth of the antenna covers the millimeter-wave (mm-wave) band (25 – 29.5 GHz) assigned for 5G communication. These features of the proposed antenna system make it a suitable candidate for 5G smart devices and sensors.

This paper presents, the design and the realization of a low-profile, compact, and broadband circularly polarized (CP) Fabry-Perot resonant antenna using a single superstrate for fifth-generation (5G) wireless multiple-input-multiple-output (MIMO) applications. The antenna consists of a corner cut patch with a diagonal slot and a superstrate. The individual resonances of the corner cut patch and patch with diagonal slot are overlapped to improve the intrinsic narrow impedance and axial ratio (AR) bandwidths of the single-fed patch antennas. A half-wavelength spaced superstrate having a half-wavelength thickness is employed as a partially reflecting surface (PRS) for high gain and wide AR as well as impedance bandwidths. The design procedure and mechanisms of the PRS are discussed in detail through the equivalent circuit and ray tracing analysis. Simulated and measured results show that the proposed antennas have a wide operational bandwidth of 25 – 33 GHz (27.6 %) for |S11| <-10 dB with a stable gain achieving a maximum value of 14.1 dBi, and a wide 3-dB AR bandwidth ranging from 26 – 31.3 GHz (17 %). This operational bandwidth of the antenna covers the proposed entire global 5G mmWave spectrum (26 – 29.5 GHz). Moreover, a 2 × 2 MIMO antenna is designed using the proposed antenna in such a way that the polarization diversity of the adjacent radiator is exploited, resulting in high isolation between antenna elements and low envelope correlation coefficient, which makes it a suitable candidate for future 5G MIMO applications.

This work presents a 4-element multiple-input multiple-output (MIMO) antenna with a single layered metasurface array for fifth generation (5G) millimeter-Wave (mm-Wave) communication systems. Each MIMO antenna element is composed of a 1×2 array with a corporate feed network. Moreover, a metasurface array structure consisting of 9×6 Circular Split Ring (CSR) shaped cells is employed to improve the gain and isolation between the MIMO antenna elements. The proposed antenna system is realized using 0.787 mm thick Rogers RT Duroid 5880 substrate. The performance of the antenna is investigated in terms of s-parameters, radiation characteristics, and MIMO parameters. The antenna operates at the mm-Wave frequency band ranging from 24.55 to 26.5 GHz. The incorporation of the metasurface layer enhanced the gain thus attaining a peak measured gain of 10.27 dBi. Additionally, isolation is also improved by 5dB after the employment of metasurface. The investigation of MIMO performance metrics such as Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Channel Capacity Loss (CCL), and Mean Effective Gain (MEG) exhibits good antenna characteristics. The demonstrated radiation properties of the proposed antenna ascertain its suitability for the forthcoming 5G communication systems.

This paper presents the design and realization of a metasurface-based low-profile wideband Circularly Polarized (CP) patch antenna with high performance for Fifth-generation (5G) communication systems. The antenna consists of a modified patch, sandwiched between an array of 4 x 4 symmetrical square ring Metasurface (MTS) and a ground plane. Initially, the intrinsic narrow bandwidth of the conventional patch antenna is increased using a diagonal rectangular slot. For further performance enhancement, the additional resonances and CP radiations are achieved for wideband operation in terms of impedance and Axial Ratio (AR) by effective excitation of surface waves propagating along the MTS. The stacking of MTS on the modified patch without any air gap resulted in an overall compact size of 1.1λ0x 1.1λ0 x 0.093λ0. Simulated and measured results show that the MTS-based antenna offers a wide impedance bandwidth ranging from 24 - 34.1 GHz (34.7%) for |S11| <; -10 with a maximum gain of 11 dBic and a 3-dB AR bandwidth of 24.1 - 29.5 GHz (20.1 %). Moreover, the proposed antenna has a smooth gain response with a small variation in its gain (9.5 - 11 dBic) and a stable left-hand CP radiation in the desired frequency range. The operating bandwidth of this antenna is covering the proposed entire global millimeter-wave spectrum (24.2 - 29.5 GHz) for 5G communication systems.

In this paper, a metasurface-based multiple-input multiple-output (MIMO) antenna with high isolation between antenna elements is presented. The main patch radiator is sandwiched between a metasurface and a ground plane to achieve performance enhancement. The fabricated single element antenna has a compact size of $0.85\lambda _{0} \times 0.85\lambda _{0} \times 0.038\lambda _{0}$ . The antenna exhibits a wideband operational bandwidth from 3.27 to 3.82 GHz for $\vert \text{S}_{11}\vert < -10$ , which corresponds to a fractional bandwidth of 15.5%. Moreover, stable radiation patterns with a peak gain of 8.1 dBi are also achieved across the operating band. The proposed single element antenna is characterized for $2 \times 2$ MIMO system by translating each antenna element orthogonal to each other. A decoupling structure consisting of slots and metallic strip with shorting pins is used to improve the isolation between the MIMO elements. The shorting pins connect the metallic strips (located between MIMO elements) on the metasurface and ground plane. These slots on ground plane and shorting pins affect the electromagnetic field distribution and consequently reduce the mutual coupling. The fabricated MIMO antenna has a compact size of $1.75\lambda _{0}\times 1.75\lambda _{0} \times 0.038\lambda _{0}$ . The proposed 4 port ( $2\times 2$ ) MIMO antenna provides 15.9% of 10 dB impedance bandwidth from 3.3 to 3.87 GHz with a peak gain of 8.72 dBi. Moreover, the proposed MIMO antenna offers excellent diversity performance, isolation between antenna elements is very high (>32dB), ECC is lower than 0.001, and diversity gain is 9.99 dB very close to the ideal value of 10dB. Owing to these features, the proposed MIMO antenna can be a good candidate for 5G Sub-6 GHz (n78 band) smart devices and sensors.