5G Antenna Research Articles

IEEE Access Special Section: Antenna and Propagation for 5G and Beyond

5G is not just the next evolution of 4G technology; it is a paradigm shift. “5G and beyond” will enable bandwidth in excess of 100s of Mb/s with a latency of less than 1 ms, in addition to providing connectivity to billions of devices. The verticals of 5G and beyond are not limited to smart transportation, industrial IoT, eHealth, smart cities, and entertainment services, transforming the way humanity lives, works, and engages with its environment.

Design of a Twelve-Port MIMO Antenna System for Multi-Mode 4G/5G Smartphone Applications Based on Characteristic Mode Analysis

This paper presents a twelve-port multiple-input multiple-output (MIMO) antenna system for multi-mode 4G/5G smartphone applications. Characteristic mode analysis (CMA) is used to illustrate the operation principle and optimize the geometrical structure of the antenna system. The proposed MIMO antenna system consists of a 4G antenna module and a 5G antenna module. The 4G antenna module is a 2 × 2 MIMO antenna array capable of covering the LTE700/2500/3400, GSM850/900, DCS, PCS, UTMS, 2.4-GHz WLAN, and 3.5-GHz WiMAX, which consists of two symmetrical antenna elements, and uses protruded ground to improve the isolation between the two adjacent 4G module antenna elements. The 5G antenna module is a 10×10 MIMO antenna array composed of ten identical monopole antennas and operates at the bands of 3.31 3.70 GHz and 4.46 5.40 GHz, covering the 3.5-GHz band (3.4 3.6 GHz) and 4.9-GHz band (4.8 5.0GHz) for 5G applications. The proposed antenna is fabricated, and the experimental results agree with the simulated results well. The calculated envelope coefficient correlation is lower than 0.5, indicating that the diversity performance meets the need of the MIMO antenna system. All the features make the antenna suitable for multi-mode 4G/5G smartphone applications.

Wideband Asymmetric Coplanar Strip Fed Antennas With Pattern Diversity for mmWave 5G Base Stations

A compact asymmetric coplanar strip (ACS)-fed mmWave 5G antenna with 6.5-7.5 dBi end-fire gain is presented in this paper. The proposed antenna is wideband, operating from 26–32 GHz with fractional bandwidth of 20.7%. The proposed single element antenna has dimensions of $6 \times 10$ mm2 demonstrating small physical and electrical footprint. The antenna achieves 1-dB gain bandwidth of 20.7% which demonstrates pattern integrity over whole operating band. The reported antenna also achieves reasonable gain for the available aperture. In order to achieve pattern diversity, a shared ground compact two-port antenna topology is next presented for beam switching at ±30°. In addition to this, a quasi-stacked beam switching module integrated with low cost 3D-printed scaffolding with wide angular coverage is proposed with adequate technical justification.

Compact Metamaterial Based $4\times4$ Butler Matrix With Improved Bandwidth for 5G Applications

This paper proposes a novel compact 4 × 4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45° phase shifter on a single FR4 substrate (er = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of -7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of -45°, 135°, -135° and +45° are achieved with a maximum average phase tolerance of 5°. The overall dimension of the BM is 70mm × 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G antenna array beamforming network.

5G evolution promoting innovation of antenna systems

We introduce the basic concept, background, and development of mobile communication systems from the first generation (1G) to the fifth generation (5G) including their antenna systems. We also describe the requirements for 5G networking and optimization of antenna systems, and present the basic principle of three-dimensional array antennas. Weight optimization methods of massive multiple-input multiple-output (MIMO) antennas are proposed and verified. Finally, several ideas are given to solve the problem of power consumption of 5G antenna systems.

Wireless 5G Radiofrequency Technology — An Overview of Small Cell Exposures, Standards and Science

5G small cell antenna systems are among the latest technologies that support wireless communications by the transmission of radiofrequency (RF) signals. Coded RF signals in the range of 0.6 to 47 GHz from fixed small cell antennas supplement wireless communications from 3G and 4G wireless systems. This paper describes the propagation of RF signals from a pole-mounted 5G antenna and how the signal strength declines with distance for a representative installation operating at 39 GHz. The far field exposure from the antenna is compared to those from multiple natural and man-made RF sources. In the United States, RF exposure standards are issued by the Federal Communications Commission. We review the history and derivation of these standards in relation to other national and international standard-setting bodies. Some have raised concern as to whether sufficient health and safety studies have been performed on RF from 5G systems, but the commonality of RF frequencies up to 300 GHz enables health agencies and standard-setting bodies to assess the potential for effects across this frequency spectrum. A 5G RF signal does not have a different mode of action than a lower frequency communication signal; both involve tissue heating at sufficient field strengths. The key difference for 5G frequencies above 6 GHz is that the body's electrical properties better limit energy deposition to a shallow depth, largely confined to superficial layers of the skin. Research to date has not provided a reliable scientific basis to conclude that RF communication signals at 5G or other frequencies will cause or contribute to adverse health effects.

Common-Aperture Sub-6 GHz and Millimeter-Wave 5G Antenna System

The realization of a common-aperture (or shared-aperture) 5G antenna system is proposed for compact and integrated wireless devices. As a combination of a dipole and tapered slots, an integrated antenna design, which operates at multi-bands, i.e. sub-6 GHz at 3.6 GHz and mm-wave at 28 GHz, is validated. The antenna design procedure starts with a dipole operating at 3.6 GHz, which is fed by a modified balun consisting of a tapered slot and a microstrip line. Here, the tapered slot has a dual feature, i.e., it is used to excite the dipole at 3.6 GHz and works as a tapered slot antenna at 28 GHz. Only a single feeder is optimized and used for both structures making the design unique and provides an extremely large frequency ratio. Moreover, the dipole's arms are utilized as an antenna footprint for two tapered slot mm-wave arrays, making the dipole dual-functional. The tapered slot antenna and the mm-wave arrays are optimized in a way that the main beams point at different directions. By this configuration, the design is able to cover an angle of 120° of space in θ-direction. As a proof of concept, a prototype is fabricated on Rogers RO-5880 with an overall size of 75 × 25 × 0.254 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The simulated and measured results confirm the validity of the proposed concept.

Design of substrate integrated waveguide to improve antenna performances for 5G mobile communication application

In this paper, a new design of substrate integrated waveguide was developed to improve the gain performance of microstrip antennas for 5G antenna applications. The antenna and substrate integrated waveguide ware designed at the frequency 28 GHz millimeter-wave band. The design of substrate integrated waveguide was developed by design an H-slot structure without a gap in the substrate layer to provide better matching impedance and reduce the loss of surface wave microstrip antenna. This study was conducted with a research and development approach through the calculation of the H-slot structure on substrate integrated waveguide and simulated by using antenna design software simulation. The numerical result shows that the new design approach for the H-slot structure without gap model was improved antenna gain and antenna size. This result has shown significant improvement compared to the circular antenna design without substrate integrated waveguide.

Performance Comparison of Evolutionary Algorithms in the Design of a Hand-Pump Shape Microstrip Antenna for 5G Applications

In this work, a single element hand-pump shape microstrip patch antenna working at 3.4 GHz–3.8 GHz for future 5G applications is proposed. The overall dimensions of the proposed antenna are 34 mm × 28 mm × 1.6 mm. In order to obtain the desired bandwidth, three rectangular slots are etched from the radiating element along with the utilization of the defected ground structure. To optimize the geometrical parameters of the proposed antenna, performance comparison of various optimization techniques viz. Particle Swarm Optimization, Bat algorithm, Differential Evolution, and Artificial Bee Colony algorithm are presented. The performance of the antenna is analyzed with the help of S-parameter, gain, and radiation efficiency. The proposed antenna is resonant at 3.6 GHz with an impedance bandwidth of 400 MHz and the radiation efficiency of 74 %, which is quite appropriate for a single element 5G antenna. Further, the suggested antenna is fabricated and experimentally tested for the validation of results.

Broadband planar antenna array for future 5G communication standards

This study presents a 5G antenna array for millimetre-wave communications. Overall size of the proposed antenna array is 40 × 15 mm 2 , and operates in a measured 23.76-42.15 GHz frequency range. A planar four-way feed network has been designed, optimised and used to excite the antenna array elements. The single element of the array is spiral monopole surrounded by a boundary of vias with extended ground plane in an inverted U-shaped manner. Hexagonal parasitic patches have been introduced at the backside to enhance impedance performance of the antenna element. Peak gain of the proposed antenna array is 11.5 dBi with radiation efficiency more than 83% in its entire operating band. The antenna gives a narrow beam-width of as low as 10.1°. Single element and its 1 × 4 array have been fabricated using standard printed circuit board (PCB) process. Measured results show excellent compliance with the simulated design objectives. The antenna is low cost, low profile with simple design and is capable of being deployed in future 5G communication mobile networks.

SLL attenuation-based thinned antenna design for next-generation communications

Among the hot issues of the Fifth Generation (5G), developing by the Third Generation Partnership Project (3GPP), advanced antenna design significantly improves the wireless communication qualities. However, limited number of researches have been published on how the smarter antenna design satisfies the 5G antenna design requirements. Hence, in this paper, we have shown that effective antenna designing techniques achieve substantial antenna performance enhancements that are essential input for the current and next-generation communication engineering. First, the excitation weights of the individual array elements are optimized to obtain enhanced antenna performances including reduced side lobe level (SLL), high directivity, reduced power consumption, and flexible radiation pattern. Then, a novel SLL attenuation technique is introduced to further reduce the SLL, power wastage, and interference. In general, the proposed technique of radiation pattern synthesis has resulted in to much better SLL reduction, directivity improvement, power wastage and interference reduction.

3D Multi-Beam and Null Synthesis by Phase-Only Control for 5G Antenna Arrays

This paper presents an iterative algorithm for the synthesis of the three-dimensional (3D) radiation pattern generated by an antenna array of arbitrary geometry. The algorithm is conceived to operate in fifth-generation (5G) millimeter-wave scenarios, thus enabling the support of multi-user mobile streaming and massive peer-to-peer communications, which require the possibility to synthesize 3D patterns with wide null regions and multiple main beams. Moreover, the proposed solution adopts a phase-only control approach to reduce the complexity of the feeding network and is characterized by a low computational cost, thanks to the closed-form expressions derived to estimate the phase of each element at the generic iteration. These expressions are obtained from the minimization of a weighted cost function that includes all the necessary constraints. To finally check its versatility in a 5G environment, the developed method is validated by numerical examples involving planar and conformal arrays, considering desired patterns with different numbers of main beams and nulls.

Millimetre-Wave Bow-Tie Reconfigurable Antenna for 5G Applications

In order to keep pace with the growing research and development on next-generation reconfigurable 5G wireless devices, this research presents a new design of flexible and low-cost 5G antenna. Instead of a conventional design, two identical back to back bow-tie antenna elements have been used on the same side of the Polyethylene terephthalate (PET) substrate with a dielectric permittivity of 3.2, loss tangent of 0.022, and a thickness of 135μm. The proposed coplanar waveguide (CPW) fed antenna is fabricated by inkjet printing using silver nanoparticles ink. The designed single element antenna is of dimensions 18.5 mm x 9.4 mm. The proposed antenna shows that it operates over a 24.2-31.5 GHz (26% fractional bandwidth, FBW) range with a return loss of 10 dB or less. The solo-element exhibits an average 5dB peak gain within the entire frequency spectrum and 99.34% of radiation efficiency with the consistent radiation pattern. The fabricated antenna was tested under different bending conditions and showed satisfactory performance. Based on the mentioned attractive results and reconfigurable characteristics of the PET substrates, the proposed antenna was found to be suitable for the 5G flexible, conformal, and body-centric applications.

Single Ring Slot-Based Antennas for Metal-Rimmed 4G/5G Smartphones

In this paper, multiband antennas based on a single ring slot are proposed for 4G/5G smartphone applications. The basic structure of the antenna is consisted of a large metal ground and an unbroken metal rim, in which a single 2 mm-wide ring slots is realized between the metal ground and rim. Here, a reconfigurable 4G antenna (820–960 and 1710–2690 MHz) is initially devised by loading multiple grounded stubs and a simple dc controlling circuit with varactor diode into the upper section of the ring slot. To further cover the sub-6 GHz spectrum (3400–3600 MHz) for future 5G communications, a four-element multi-input multi-output (MIMO) slot antennas configuration is designed by utilizing the lower section of the ring slot. A prototype antenna was fabricated, and good agreement is shown between the measured and simulated results. Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and compact structure, the proposed antenna design is attractive for 4G/5G smartphones.

Integrated Millimeter-Wave Wideband End-Fire 5G Beam Steerable Array and Low-Frequency 4G LTE Antenna in Mobile Terminals

In this paper, a novel technique of collocating a millimeter-wave end-fire 5G beam steerable array antenna with a low-frequency planar inverted-F antenna (PIFA) is presented. In this technique, the low-frequency antenna can be transparent by using some grating strips between the low- and high-frequency antennas. A quad-element mm-wave array with end-fire radiation patterns operating in 22–31 GHz is integrated with a dual-band low-frequency PIFA in a mobile terminal. The novelty of this paper is the collocation of a high-frequency end-fire 5G antenna array with an old-generation low-frequency antenna, such as 4G in small space in the mobile terminal, without interfering with the radiation pattern and impedance matching of both low- and high-frequency antennas. The proposed 5G antenna covers 22–31 GHz and can scan ±50° with the scan loss of better than 3 dB. The coverage efficiency of the proposed mm-wave 5G antenna is better than 50% and 80% for a minimum gain of 4 and 0 dBi in 22–31 GHz, respectively. The gain of the high-frequency antenna array is better than 9.5 dBi at 28 GHz. The low-frequency antenna covers some practical 4G LTE bands from 740–960 MHz and 1.7–2.2 GHz bands. The measured results in both low and high frequencies agree well with the simulations.

Design of Dual Band 5G Antenna Array with SAR Analysis for Future Mobile Handsets

This paper presents the design and specific absorption rate (SAR) analysis of the dual band antenna array for the future fifth generation (5G) mobile communication. The proposed antenna array operates in the Ka-band, at 28 and 38 GHz frequency bands. Roggers-5880 is used as a substrate having relative permittivity, thickness and loss tangent of 2.2, 0.254 mm and 0.0009 respectively in the proposed antenna array design. The main lobe gain of the single element 5G antenna is 7.71 and 7.73 dB at 28 and 38 GHz resonance frequencies correspondingly. As the gain requirement for 5G mobile communication system is 12 dB, thus 2 × 2 and 1 × 4 antenna arrays are designed to achieve the desired gain. The 2 × 2 antenna array yields a bore side gain of 12.3 and 15 dB, while 1 × 4 antenna array gives a bore side gain of 12.5 and 12.1 dB at 28 at 38 GHz frequency bands correspondingly. The dual band antenna (single element, antenna arrays) matched with a VSWR < 1.16 in the two frequency bands. All the simulations are carried out using computer simulation technology software. The SAR analysis averaged over 10 g of tissue of the proposed dual band 2 × 2 antenna array has been carried out on the head of human body using X-finite difference time domain electromagnetic simulation software, giving a safer limit of 0.37 and 1.34 W/kg < 2 W/kg according to the European IEC Standard at 28 and 38 GHz frequency bands correspondingly. The proposed antenna array is a suitable contender for the future 5G mobile handheld devices.

Sub-6GHz 4G/5G Conformal Glasses Antennas

The difficulty of antenna design applied to glasses is that the structure of glasses is too single, and the space available for antenna design is greatly limited. In this background, the integrated design of 4G antennas and 5G antennas applied to glasses is proposed in this paper. The most important highlight of this design is that it makes full use of the limited three-dimensional space structure provided by glasses and achieves the perfect combination of the antenna and glasses in the physical structure. Specifically, two antennas for 4G communication are arranged on two glasses frames, and four antennas for 5G communication are arranged on two glasses legs. In this way, we can make full use of the space provided by the glasses to design antennas and ensure that there is a certain distance between the 4G antennas and 5G antennas so that the performance of both 4G antennas and 5G antennas can be guaranteed. The 4G antenna consists of a loop structure printed on the frame and leg of the glasses and a parasitic branch strip printed on the front of the leg of the glasses. The resonance modes of the 4G antenna are mainly loop, monopole, and dipole modes, which can cover two 4G bands of 0.824-0.96 GHz and 1.71-2.69 GHz. Each 5G antenna mainly comes from the open slot mode etched on the metal ground surface of an FR4 substrate of the glasses leg. In addition, the slot antennas operate in two 5G bands of 3.3-3.6 GHz and 4.8-5.0 GHz. Finally, the glasses and the antennas are fabricated based on FR4 substrates and measured. The measured results show that the proposed antennas perform well and have the potential to be used in 4G/5G communications through glasses.

MIMO Antenna System for Multi-Band Millimeter-Wave 5G and Wideband 4G Mobile Communications

A multiple-input multiple-output (MIMO) antenna system is proposed for fifth generation (5G) and fourth generation (4G) mobile communication. The design meets all of the requirements of both 5G and 4G antennas using only a single structure. Since 5G will work at millimeter-wave (mm-Wave), the proposed design serves triple bands at mm-Wave (28, 37 and 39 GHz) for 5G in addition to 2 GHz band (1.8–2.6) for 4G. Each MIMO element consists of a slot-based antenna, fed by two microstrip feeders for the 5G and 4G bands. The design works as a tapered slot antenna at mm-Wave offering end-fire radiation for 5G and works as an open-ended slot antenna for a 2 GHz band offering omni-direction radiation for 4G. The slot antenna type used in the proposed design produces wide bandwidths for the 5G and 4G. The overall volume of each MIMO antenna element is $0.21\times 0.10 \times 0.003\,\,\lambda ^{3}$ , where $\lambda $ is the wavelength of the lowest operating frequency. As a proof of concept, a prototype is developed and tested. The measured results show a wide impedance bandwidth of $|S_{11}| −10 dB covering the band 27.5–40 GHz for 5G, and impedance bandwidth of $|S_{11}| −6 dB covering the band 1.8–2.6 GHz for 4G.

Wideband MIMO Antenna Systems Based on Coupled-Loop Antenna for 5G N77/N78/N79 Applications in Mobile Terminals

A wideband 8-antenna multiple-input and multiple-output (MIMO) system that can cover 3.3-5.0 GHz is proposed for the 5G new radio N77/N78/N79 application in mobile phones. The wide bandwidth of the MIMO antenna system is obtained by the proposed coupled-loop antenna, which has three coupling sections located separately at its top central and two sides. Due to this special arrangement, the coupled-loop antenna can support three resonance modes of loop antenna: 0.5λ, 0.75λ, and 1.0λ modes. The distinctive feature of the proposed coupled-loop antenna design is that it can excite the 0.75λ modes, which has not been reported before. The wide bandwidth is obtained by the combination of the three resonance modes. To evaluate the performance of the proposed 8 × 8 MIMO antenna system, the antenna isolation, envelope correlation coefficient (ECC), and channel capacity (CC) are all investigated. Antenna prototypes for an 8-antenna MIMO system located along the edge of mobile phones are fabricated and measured, and; quite good agreements between simulation and measurement are obtained.

An Integrated Antenna System for 4G and Millimeter-Wave 5G Future Handheld Devices

In this work, an integrated antenna system with Defected Ground Structure (DGS) is presented for Fourth Generation (4G) and millimeter (mm)-wave Fifth Generation (5G) wireless applications and handheld devices. The proposed design with overall dimensions of 110 mm × 75 mm is modeled on 0.508 mm thick Rogers RT/Duroid 5880 substrate. Radiating structure consists of antenna arrays excited by the T-shape 1 × 2 power divider/combiner. Dual bands for 4G centered at 3.8 GHz and 5.5 GHz are attained, whereas the 10-dB impedance bandwidth of 24.4 - 29.3 GHz is achieved for the 5G antenna array. In addition, a peak gain of 5.41 dBi is demonstrated across the operating bandwidth of the 4G antenna array. Similarly, for the 5G mm-wave configuration the attained peak gain is 10.29 dBi. Moreover, significant isolation is obtained between the two antenna modules ensuring efficient dual-frequency band operation using a single integrated solution. To endorse the concept, antenna prototype is fabricated and far-field measurements are procured. Simulated and measured results exhibit coherence. Also the proposed design is investigated for the beam steering capability of the mm-wave 5G antenna array using CST®MWS®. The demonstrated structure offers various advantages including compactness, wide bandwidth, high gain, and planar configuration. Hence, the attained radiation characteristics prove the suitability of the proposed design for the current and future wireless handheld devices.