A 12-port antenna array operating in the long term evolution (LTE) band 42 (3400–3600 MHz), LTE band 43 (3600–3800 MHz), and LTE band 46 (5150–5925 MHz) for 5G massive multiple-input multiple-output (MIMO) applications in mobile handsets is presented. The proposed MIMO antenna is composed of three different antenna element types, namely, inverted $\pi $ -shaped antenna, longer inverted L-shaped open slot antenna, and shorter inverted L-shaped open slot antenna. In total, eight antenna elements are used for the $8 \times 8$ MIMO in LTE bands 42/43, and six antenna elements are designed for the $6 \times 6$ MIMO in LTE band 46. The proposed antenna was simulated, and a prototype was fabricated and tested. The measured results show that the LTE bands 42/43/46 are satisfied with reflection coefficient better than −6 dB, isolation lower than −12 dB, and total efficiencies of higher than 40%. In addition to that, the proposed antenna array has also shown good MIMO performances with an envelope correlation coefficient lower than 0.15, and ergodic channel capacities higher than 34 and 26.5 b/s/Hz in the LTE bands 42/43 and LTE band 46, respectively. The hand phantom effects are also investigated, and the results show that the proposed antenna array can still exhibit good radiation and MIMO performances when operating under data mode and read mode conditions.

12-Port 5G Massive MIMO Antenna Array in Sub-6GHz Mobile Handset for LTE Bands 42/43/46 Applications

This article presents a wideband orthogonal-mode dual-antenna pair with a shared radiator for fifth-generation (5G) multiple-input multiple-output (MIMO) metal-rimmed smartphones. The wideband decoupling property of the dual-antenna pair is realized by the combination of the orthogonal monopole/dipole modes in the lower band and the orthogonal slot/open-slot modes in the higher band. With the orthogonal-mode design scheme, the dual-antenna pair shows a wide impedance bandwidth of 3.3–5.0 GHz and a high isolation of more than 21.0 dB across the entire band without using any external decoupling structures. By arranging four such dual-antenna pairs at two side edges of the smartphone, an $8 \times 8$ MIMO system is fulfilled. Both the simulation and measurement results show that the proposed $8 \times 8$ MIMO system could offer an isolation of better than 12.0 dB and an envelope correlation coefficient of lower than 0.11 between all ports. The measured average antenna efficiencies are 74.7% and 57.8% for the two antenna elements of the dual-antenna pair. We portend that the proposed design scheme, with merits of shared radiator, wide bandwidth, and metal rim compatibility, has the potential for the application of future 5G smartphones.

Wideband 5G MIMO Antenna With Integrated Orthogonal-Mode Dual-Antenna Pairs for Metal-Rimmed Smartphones

The intensive research in the fifth generation (5G) technology is a clear indication of technological revolution to meet the ever-increasing demand and needs for high speed communication as well as Internet of Thing (IoT) based applications. The timely upgradation in 5G technology standards is released by third generation partnership project (3GPP) which enables the researchers to refine the research objectives and contribute towards the development. The 5G technology will be supported by not only smartphones but also different IoT devices to provide different services like smart building, smart city, and many more which will require a 5G antenna with low latency, low path loss, and stable radiation pattern. This paper provides a comprehensive study of different antenna designs considering various 5G antenna design aspects like compactness, efficiency, isolation, etc. This review paper elaborates the state-of-the-art research on the different types of antennas with their performance enhancement techniques for 5G technology in recent years. Also, this paper precisely covers 5G specifications and categorization of antennas followed by a comparative analysis of different antenna designs. Till now, many 5G antenna designs have been proposed by the different researchers, but an exhaustive review of different types of 5G antenna with their performance enhancement method is not yet done. So, in this paper, we have attempted to explore the different types of 5G antenna designs, their performance enhancement techniques, comparison, and future breakthroughs in a holistic way.

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Fifth Generation Antennas: A Comprehensive Review of Design and Performance Enhancement Techniques

A design of an ultra-wideband eight-port multiple-input multiple-output (MIMO) antenna array in a smartphone with an open-slot metal frame for fifth-generation (5G) communications is presented. Each element is fed by a microstrip line with a tuning stub, consisting of a U-slot on the ground plane and an open slot on the metal frame. Each slot element on the ground only occupies an area of 15 x3 mm. The antenna array can operate in 3.3-6 GHz (S
 11
 <; -6 dB) that is ultra-wide bandwidth for the future 5G communications. The antenna array is manufactured and measured. Measured antenna isolation is higher than 11 dB without any decoupling structures applied. Moreover, measured radiation patterns, antenna efficiencies, and envelop correlation coefficients are also given in this paper. High agreement between the measured and simulated results is obtained, which means that the proposed antenna is promising in engineering application.

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Ultra-Wideband 8-Port MIMO Antenna Array for 5G Metal-Frame Smartphones

For the first time, zero-ground-clearance dual antenna pair with high isolation and balanced high performance is proposed. A T-shaped monopole intersects with a T-shaped slot that is etched on a large ground edge, constituting the CPW-fed dual antenna pair. By exploiting the odd and even modes of the CPW structure, two orthogonal characteristic modes including the in-phase current and monopole modes can be excited, generating high port isolation. Both modes are unbalanced mode, which means that the ground currents can be fully excited, so the two antennas are with balanced high performance. A sub-6 GHz antenna pair that occupies a footprint of $15\times 7$ mm2 ( $0.18\,\,\lambda \,\times 0.08\,\,\lambda$ ) is analyzed and the simulated results show an isolation of better than −24 dB and an envelope correlation coefficient (ECC) of lower than 0.0016, −6 dB bandwidths of 230 and 240 MHz, and average efficiencies of 57.9% and 57.4%. A four-antenna multiple-input multiple-output (MIMO) array is fabricated and measured to verify the feasibility. The measured isolations and ECCs of the two modes are, respectively, better than −20.0 dB and 0.04, −6 dB bandwidths are 230 MHz/240 MHz and 220 MHz/230 MHz, and average efficiencies are 54.5%/50.2% and 49.9%/48.6%. The proposed dual antenna pair exhibits a great potential for 5G MIMO smartphone application.

Orthogonally Polarized Dual Antenna Pair With High Isolation and Balanced High Performance for 5G MIMO Smartphone

An octa-band antenna for 5.7-in mobile phones with the size of 80 mm × 6 mm × 5.8 mm is proposed and studied. The proposed antenna is composed of a coupled line, a monopole branch, and a ground branch. By using the 0.25-, 0.5-, and 0.75-wavelength modes, the lower band (704-960 MHz) and the higher band (1710-2690 MHz) are covered. The working mechanism is analyzed based on the S-parameters and the surface current distributions. The attractive merits of the proposed antenna are that the nonground portion height is only 6 mm and any lumped element is not used. A prototype of the proposed antenna is fabricated and measured. The measured -6 dB impedance bandwidths are 350 MHz (0.67-1.02 GHz) and 1.27 GHz (1.65-2.92 GHz) at the lower and higher bands, respectively, which can cover the LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS, LTE2300, and LTE2500 bands. The measured patterns, gains, and efficiencies are presented.

An Octa-band Monopole Antenna With a Small Nonground Portion Height for LTE/WLAN Mobile Phones

This letter presents a compact eight-band monopole antenna whose size is 70 mm × 7 mm × 6 mm for LTE metal-frame mobile phones. The mainly radiating part of the proposed antenna is the metal frame. There are three gaps with the same size of 1 mm in the frame, and these gaps divide the antenna into two parts. Besides, a match circuit is used to enlarge the bandwidth and make the lower band matched. The advantage of the proposed antenna is that eight bands can be covered with a metal frame under the condition of only a 7 mm ground clearance. A prototype is manufactured and tested. The measured –6 dB impedance bandwidths are 375 MHz (0.675–1.05 GHz) and 1.2 GHz (1.6–2.8 GHz). The LTE700, GSM850, GSM900, GSM1800, GSM1900, UMTS, LTE2300, and LTE2500 bands are covered. The measured efficiencies are 52.7%–78.7% at the lower band and 45.6%–81% at the higher band. The measured gains are 0–2.1 dBi at the lower band and 1.6–3.6 dBi at the higher band.

Eight-Band Antenna With A Small Ground Clearance for LTE Metal-Frame Mobile Phone Applications

This letter presents a wideband/multiband quad-antenna system for 4G/5G/GPS metal-frame mobile phones. The quad-antenna system has two kinds of antenna elements and four antenna elements. The merit of the proposed antenna system is that a quad-antenna system is achieved under the condition of metal frame, and without using any decoupling structure, the desired bands for 4G/5G/GPS are covered. A prototype was fabricated and measured. For the first kind of antenna elements (including two antenna elements), the bands of 698–960, 1710–2690, and 3400–3600 MHz are covered, and the LTE700/GSM850/GSM900/GSM1800/GSM1900/LTE2300/LTE2500/3.5 GHz bands all are covered. For the second kind of antenna elements (including two antenna elements), the bands of 1440–2690 and 3400–3600 MHz are covered, and the GPS, GSM1800/GSM1900/LTE2300/LTE2500/3.5 GHz bands are covered. The measured isolations are bigger than 10 dB. The measured efficiencies are bigger than 40% at all the working bands. The measured envelope correlation coefficients are very suitable for multiple-input--multiple-output (MIMO) communication systems.

A Quad-Antenna System for 4G/5G/GPS Metal Frame Mobile Phones

This paper presents an eight-band antenna for full-screen metal frame LTE mobile phones with a size of 142 mm $\times79$ mm $\times7.5$ mm. The proposed antenna mainly consists of two monopole branches, a match circuit, and two ground branches. The two monopole branches and the match circuit are used to cover the lower band (698–960 MHz) and part of the higher band (1710–2690 MHz). One of the two ground branches is used to cover the other part of the higher band, and the other is mainly used to make the lower band matched. The merit of the proposed antenna is that eight bands can be realized under the conditions of an only 2 mm ground clearance and a metal frame; it is very suitable for full-screen metal frame mobile phones. A prototype is manufactured and measured. The measured −6 dB impedance bandwidths are 300 MHz (665–965 MHz) at the lower band and 1190 MHz (1610–2800 MHz) at the higher band. The LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, and LTE2500 bands are covered. The measured efficiency is bigger than 42%, so it is practical for mobile phone applications.

Eight-Band Antenna for Full-Screen Metal Frame LTE Mobile Phones

A low-profile microstrip antenna that has a broad impedance bandwidth by exciting three resonant modes is proposed. The proposed antenna mainly consists of a grid-slotted radiation patch, a metal ground, four vertical metal strips, and a vertical grounded balun feeding structure. The TM10, TM12, and antiphase TM22 modes are excited simultaneously. The vertical grounded balun feeding structure is used to avoid etching slot on the metal ground to get a high front-to-back ratio. The four vertical metal strips are introduced to enhance the impedance matching and reduce the sidelobe of the radiation pattern of the antiphase TM22 mode. With a profile of 0.07 λ 0 ( λ 0 is the center operating wavelength in the free space), the measured −15 dB impedance operating band is 3.31–4.31 GHz, and the relative bandwidth is 26.2%. The measured front-to-back ratio is larger than 16 dB, and the sidelobe level is lower than −10 dB. The proposed antenna has a stable broadside radiation performance in the operating band.

Daiwei Huang

Papers

An Octa-band Monopole Antenna With a Small Nonground Portion Height for LTE/WLAN Mobile Phones

Eight-Band Antenna With A Small Ground Clearance for LTE Metal-Frame Mobile Phone Applications

A Quad-Antenna System for 4G/5G/GPS Metal Frame Mobile Phones

Eight-Band Antenna for Full-Screen Metal Frame LTE Mobile Phones

A Broadband Low-Profile Multimode Microstrip Antenna