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 × 2 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 1.0λ0 × 1.0λ0 × 0.04λ0. 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 × 2) 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 broadband circularly polarized (CP) Fabry-Perot resonant antenna using a single superstrate for the fifth-generation (5G) wireless multipleinput-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 |S 11 | < −10 dB with a stable gain achieving a maximum value of 14.1 dBiC 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 millimeter wave (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.INDEX TERMS Fifth-generation (5G), millimeter wave, MIMO antenna, Fabry-Perot resonant antenna.

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 × 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 1.1λ 0 × 1.1λ 0 × 0.093λ 0. Simulated and measured results show that the MTS-based antenna offers a wide impedance bandwidth ranging from 24-34.1 GHz (34.7%) for |S 11 | < −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. INDEX TERMS Metasurface-based antenna, circular polarization, 5G technology, millimeter-wave.

This paper presents the design and realization of a compact ultra-wideband (UWB) antenna with a rectangular notch wireless area network (WLAN) band that has controllable notched bandwidth and center frequency. The UWB characteristics of the antenna are achieved by truncating the lower ends of the rectangular microstrip patch, and the notch characteristics are obtained by using electromagnetic bandgap (EBG) structures. EBGs consist of two rectangular metallic conductors loaded on the back of the radiator, which is connected to the patch by shorting pins. A rectangular notch at the WLAN band with high selectivity is realized by tuning the individual resonant frequencies of the EBGs and merging them. Furthermore, the results show that the bandwidth and frequency of the rectangular notch band could be controlled according to the on-demand rejection band applications. In the demonstration, the rectangular notch band was shifted to X-band satellite communication by tuning the EBG parameters. The simulated and measured results show that the proposed antenna has an operational bandwidth from 3.1–12.5 GHz for |S11| < -10 with a rectangular notch band from 5–6 GHz, thus rejecting WLAN band signals. The antenna also has additional advantages: the overall size of the compact antenna is 16 × 25 × 1.52 mm3 and it has stable gain and radiation patterns.