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.

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 0.85λ0 × 0.85λ0 × 0.038λ0. The antenna exhibits a wideband operational bandwidth from 3.27 to 3.82 GHz for |S11| < −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 × 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 1.75λ0 × 1.75λ0 × 0.038λ0. The proposed 4 port (2×2) 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.

This article presents the design and realization of a compact ultra‐wideband (UWB) antenna with on‐demand WLAN band‐rejection. The antenna consists of a simple truncated rectangular patch with a U‐slot and a partial ground plane, which are both patterned on Taconic TLY‐5 substrate (εr = 2.2). The lower corners of the patch are truncated with a semicircle to realize wideband characteristic, while the notch is obtained by etching a U‐slot on the radiating patch. The proposed antenna outperforms the existing UWB antennas owing to its compact size, radiation stability, and very wide impedance bandwidth. Simulated and measured results show that the novel antenna has a very wide operating bandwidth of 2.9‐23.5 GHz with a VSWR <2, and a notch band from 4.9 to 6.1 GHz to reject IEEE 802.11a and HIPERLAN/2 frequency band. The antenna offers promising performances including moderate gain (Gmax = 6.1 dB), nearly omnidirectional stable radiation patterns, and a compact overall size of 13 × 22 × 0.8 mm3. Besides of the other advantages, this antenna design presents mechanical robustness, easy integration into circuit boards, and excellent low‐cost mass production suitability.

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This article presents a millimeter‐wave (mmWave) microstrip patch antenna (MPA) with a vertically coupled split ring metaplate (VCSRM). The narrow bandwidth and low gain of MPA are improved using VCSRM by periodically arranging split rings on the front and backsides of a dielectric slab. Numerical and experimental results show that the proposed antenna attains good radiation pattern, a high gain of 11.94 dBi, and a measured fractional bandwidth covering 26.58 to 29.31 GHz (9.77%). The gain of the antenna is increased by 5.35 dBi and the bandwidth is improved by 3.87% when compared to MPA without VCSRM. Thus, the proposed antenna with a small size of 18 × 22 mm2 is suitable for mmWave applications.