Proposed Multiple-input Multiple-output Antenna System Research Articles

Side-edge dual-band MIMO antenna system for 5G cellular devices

An eight-element multiple-input multiple-output (MIMO) antenna system is presented for two distinct 5G allocated bands, i.e., 3.5 and 5.2 GHz. The MIMO radiating elements are printed on each side of the mobile phone chassis, having dimensions of 150 × 7 mm2, while the microstrip feeding lines fed through a coaxial connector are printed on the main board, having dimensions of 150 × 75 mm2. The single element of the MIMO antenna system consists of a modified slotted rectangular patch radiator. One slot is composed of a hybrid shape (which consists of both T- and L-shaped patterns), and the second one is a typical inverted L-shaped slot. The placement of slots generated two different current paths, which led to dual-band response at 3.5 and 5.2 GHz. In the MIMO configuration, the arrangement of radiating elements ensures pattern diversity characteristics, which are useful for MIMO systems. Furthermore, the MIMO antenna system offers a minimum isolation of 13.5 and 21.5 dB at 3.5 and 5.2 GHz, respectively. From the results, it is also observed that the radiating elements offer a radiation efficiency of ≥70% at 3.5 GHz, while at 5.2 GHz, the radiation efficiency is noted to be >55% with acceptable gain. A comprehensive analysis of key performance parameters, e.g., envelope correlation coefficient (ECC), mean effective gain (MEG), and channel capacity (CC), was conducted, and it is noted that the proposed MIMO antenna system exhibits an ECC of less than 0.015, MEG of < −3 dB, and CC of 39.5 bps/Hz. In addition, the specific absorption rate (SAR) analysis of the proposed MIMO antenna was conducted and observed a value of 1.35 and 1.05 W/Kg at 3.5 and 5.2 GHz, respectively. To verify the computed results, a prototype of the proposed MIMO antenna was fabricated and subjected to thorough measurements. It was observed that the measured results satisfied the simulated data and aligned excellently with the measured data. Based on the performance of the proposed MIMO antenna, it became evident that the MIMO antenna structure can be used as a potential candidate for future fifth-generation (5G)-enabled smart phones.

Compact eight-element MIMO antenna array for sub 6 GHz Mobile applications

A compact eight-element multiple-input multiple-output (MIMO) antenna array operating at the sub-6-GHz (LTE band 52) for the 5G handheld applications is proposed. The antenna array is realized by employing eight couple-fed slots etched on the ground plane of the MIMO antenna system. The size of the slot radiators excites the required operating bandwidth. A parametric analysis study of the effect of varying the size of the slot radiators on the ground plane is provided to give some insight into the operation of the proposed antenna system. The radiators are excited by 50-Ω strip lines. Rectangular-shaped slits are used as isolation structures to mitigate the mutual coupling effect between elements, resulting in a low Envelope Correlation Coefficient (ECC) of less than 0.1 at the operating bandwidth. The proposed MIMO antenna was fabricated and experimentally validated. The measured and simulated results are in good agreement. Other MIMO performance indicators, such as radiation patterns, Mean Effective Gain (MEG), and the proposed MIMO antenna system’s total efficiencies, are being analyzed. Measurements and simulation results are consistent, which shows that the proposed antenna is a good candidate for 5G applications in the LTE band 52.

Higher Order MIMO Antenna Design Using Capacitively Coupled Meandered Loop Element for 5G Smartphone Applications

In this paper, a compact 10-element multiple-input multiple-output (MIMO) antenna system for fifth generation (5G) wireless communication system is presented. The antenna structure has a T-shaped feeding element and a reduced size capacitively coupled meandered loop radiating element. The proposed MIMO antenna system is operating at 3.5 GHz. The MIMO antenna element is self-isolated and it has a compact size of 13.45×6 mm2. It exhibits very good isolation of more than 15 dB without using any external decoupling structure like a neutralization line or slot technique. Furthermore, performance parameters like total efficiency are around 40-64%, envelope correlation coefficient (ECC) is below 0.02, while gain of all antennas is between 3-3.4dBi. The performance of the proposed MIMO antenna is also verified through the measurement of its fabricated prototype. In this paper, a compact 10-element multiple-input multiple-output (MIMO) antenna system for fifth generation (5G) wireless communication system is presented.

A Novel Shaped Four Port MIMO Antenna for Wireless Communication

This paper presents a compact novel shaped micro strip line fed four element Multiple Input Multiple Output (MIMO) antenna for wireless application at 2.4 GHz. Four vertically oriented identical rectangular patch antennas are used to form a hollow cylinder of rectangular cross section. The direction of radiation of each antenna is thus oriented at 900 with respect to its two adjacent antennas providing good isolation between adjacent antennas in this compact MIMO system. Each antenna element has the dimensions of 0.30λx0.38λx0.012λ. The whole MIMO antenna has the outer dimensions of 0.38λx0.38λx0.30λ. The uniqueness of the proposed MIMO antenna is that the inner space of the hollow cylindrical structure can be used for hosting the associated signal processing unit of the whole system. Performance parameters of the proposed MIMO antenna are investigated using Computer Simulation Technology (CST). Envelope Correlation Coefficient (ECC) less than 0.033 and almost 10dB Diversity Gain (DG) are obtained at 2.4 GHz for this simple and compact antenna system. Ratio of Mean Effective Gain (MEG) of any two antennas is less than 0.02dB. Performance parameters of the proposed MIMO antenna system are compared with similar types of antennas found in recent literature.

Circularly polarized three-element MIMO antenna with diversity and polarization reconfigurability techniques

This paper proposes a circularly polarized (CP) three-element multiple-input multiple-output (MIMO) antenna system with diversity and polarization reconfigurability techniques for wireless local-area network (WLAN) applications. The proposed MIMO antenna system employs two CP antennas with endfire characteristics and a broadside slot antenna. The polarization reconfigurability technique is achieved using pin diodes in all three antenna elements. Additionally, the three antennas have distinct directional radiation patterns, improving the MIMO antenna system's diversity performance. The three-element MIMO antenna system is fabricated for validation, and antenna parameters are measured. For all the states, the proposed antenna provides good antenna characteristics for the WLAN frequency band (5.15 GHz − 5.35 GHz). The three-element MIMO antenna exhibits good port-to-port isolation, and MIMO parameters like total active reflection coefficient (TARC), channel capacity loss (CCL), envelope correlation coefficient (ECC) and diversity gain (DG) are within the acceptable range.

A multi-band MIMO antenna system with coupled-fed modified rectangular patch elements for 5G systems

A four-port multiple input multiple output (MIMO) antenna system constructed of four compact dual-band (38/60 GHz) microstrip patch antennas is proposed for 5G mobile applications. Each individual element is optimized to achieve the desired performance of the overall MIMO system. Numerical and experimental investigations are achieved to assess the performance of both the single-element antenna and the four-port MIMO antenna system. It is shown that the simulation results agree with the experimental measurements, and both show good performance of the proposed MIMO antenna system. The bandwidths achieved around 38 GHz and 60 GHz are about 2 GHz and 3.2 GHz, respectively. The performance of the MIMO antenna system including the return loss at each antenna port and the coupling coefficients between the different ports are investigated. The radiation patterns produced when each port is excited alone are shown to be suitable for spatial diversity scheme. They have a high radiation efficiency exhibited by a balloon-like shaped radiation pattern for both the upper and lower frequency bands. It is shown that the envelope correlation coefficient (ECC) and the diversity gain (DG) are suitable for performance for the targeted 5G bands.

A Compact mmWave MIMO Antenna for Future Wireless Networks

This article presents a four-element multiple-input multiple-output (MIMO) antenna design for next-generation millimeter-wave (mmWave) communication systems. The single antenna element of the MIMO systems consists of a T-shaped and plow-shaped patch radiator designed on an ultra-thin Rogers RT/Duroid 5880 substrate. The dimensions of the single antenna are 10 × 12 mm2. The MIMO system is designed by placing four elements in a polarization diversity configuration whose overall dimensions are 24 × 24 mm2. From the measured results, it is observed that the MIMO antenna provides 9.23 GHz impedance bandwidth ranging from 22.43 to 31.66 GHz. In addition, without the utilization of any decoupling network, a minimum isolation of 25 dB is achieved between adjacent MIMO elements. Furthermore, the proposed MIMO antenna system is fabricated, and it is noted that the simulated results are in good agreement with the measured results. Through the achieved results, it can be said that the proposed MIMO antenna system can be used in 5G mmWave radio frequency (RF) front-ends.

Isolation enhancement in dual-band MIMO antenna by using metamaterial and slot structures for WLAN applications

A dual-band multiple-input multiple-output (MIMO) antenna with enhanced isolation operating in 2.35–2.50 GHz and 5.13–5.88 GHz bands is investigated and presented. The proposed antenna system is deformed from two inverted-F antennas, and the distance between the antenna elements is only 0.104 (—wavelength of 2.4 GHz). To enhance isolation and reduce mutual coupling, the metamaterial and slot structures are efficiently and innovatively designed on the ground plane for two bands. Both decoupling methods effectively improve the antenna isolation, with metamaterials acting on the lower band and slots acting on the higher band. The mutual coupling at 2.4 GHz and 5.5 GHz is reduced by 15.24 dB and 8.19 dB, respectively. Then, the optimized MIMO antenna can cover both 2.4 GHz and 5 GHz wireless local area network (WLAN) bands, and has the advantages of wideband, compact size, good radiation, enhanced isolation, and low envelope correlation coefficient. The measured results agree with the simulated results, which shows that the proposed MIMO antenna system has potential application value in WLAN system.

MmWave Four-Element MIMO Antenna for Future 5G Systems

This paper presents an S-shape four-port Multiple Input Multiple Output (MIMO) wideband mmWave antenna with bandwidth of 25 GHz to 39 GHz. The antenna is designed on 0.254 mm ultra-thin RO5880 with permittivity of 2.3. The dimensions of proposed S-shape antenna are 10 × 12 mm for single element and 24 × 24 mm for four-port MIMO configuration. A decoupling network is introduced to further compress mutual coupling among MIMO elements. The peak gain achieved is 7.1 dBi and MIMO assembly delivers diversity scheme. The proposed MIMO antenna is fabricated, and simulated results are found to be in excellent agreement with simulations. Through the results obtained, the proposed MIMO antenna system can be considered as a potential candidate for future mmWave devices.

Three‐port circularly polarized MIMO antenna for WLAN application with pattern and polarization diversity

AbstractIn this article, a three‐port circularly polarized (CP) multiple‐input multiple‐output (MIMO) antenna for wireless local area network (WLAN) application with pattern and polarization diversity is proposed. The proposed MIMO antenna system comprises of a broadside CP antenna element with a T‐shaped slot and two endfire CP antenna elements. Good impedance bandwidth of 16.9% and 5.5% are achieved by the broadside CP antenna and endfire CP antenna, respectively, and their corresponding axial ratio (AR) bandwidth is 7% and 10.47%. The isolation between the different antenna elements is better than 20 dB, and the polarization purity for all CP antenna is more than 25 dB along with the maximum radiation.

Frequency reconfigurable Yagi‐like MIMO antenna system with a wideband reflector

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based on a single-layer geometry unlike complex multi-layer reflectors used in the literature. It improves the front-to-back ratio between 5 and 17 dB in the entire frequency range covering 2.5–4.5 GHz. The proposed reconfigurable MIMO antenna system covers the LTE and WiMAX bands with a minimum measured bandwidth of 200 MHz per covered bands. The frequency reconfigurability is achieved by reactively loading the slot loop with varactor diodes. The overall size of the proposed antenna system is 40 × 100 × 0.76 mm 3 , making it suitable for tablet handheld devices and access points. It has a maximum measured peak gain of 5 dBi and total measured radiation efficiency of 78%. The proposed MIMO antenna system has port isolation of > 10 dB within the entire band of operation. The radiation patterns are isolated in space from each other and ensure very low envelope correlation coefficient.

A Compact and Straightforward Self-Decoupled MIMO Antenna System for 5G Applications

This study investigates a compact and straightforward self-decoupled $2\times 2$ multiple-input multiple-output (MIMO) antenna set and its applications for current and future 5G terminal devices. The proposed self-decoupled MIMO antennas include a popularly used loop antenna and a compact loop-type ground-radiation antenna without utilizing any supplementary decoupling structures or undergoing complex tuning process. It is revealed that the loop antenna and the ground-radiation antenna can be modeled as an electric-current element and a magnetic-current element, respectively. This orthogonality allows the self-decoupled characteristic of the proposed MIMO antennas even though the antenna elements are tightly arranged and collocated together. An $8\times 8$ MIMO antenna system is further demonstrated for 5G MIMO applications, where both simulation and measurement are conducted to validate the feasibility of the proposed technique. It is concluded that the proposed MIMO antenna system is a smart way to generate high isolation and low correlation characteristics while having advantages of low profile and easy fabrication so that it can be recognized as a promising candidate for 5G applications.

Eight-Port Metamaterial Loaded UWB-MIMO Antenna System for 3D System-in-Package Applications

In this article, an eight-element ultra-wideband (UWB) Multiple-Input-Multiple Output (MIMO) antenna system is proposed for 3D non-planar applications. The proposed UWB-MIMO antenna is installed around a polystyrene block in the 3D-octagonal arrangement. The eight radiating elements are placed on the sides of the octagonal polystyrene block with top and bottom surfaces left open. The single antenna element consists of a modified Y-shaped radiating patch, epsilon-negative (ENG) metamaterial, and a partial ground plane. A modified pie-shaped decoupling structure is deployed at the back-side of the radiating patch to improve the isolation among array elements. Each antenna element is printed on a low-cost FR-4 substrate with dimensions of 28 mm $\times23$ mm with coverage of the whole UWB spectrum from 3.1 to 10.6 GHz frequency band. The eight-port UWB-MIMO antenna system consists of symmetric and non-symmetric array configurations. Simulated and measured MIMO performance parameters i.e. Channel Capacity Loss (CCL) < 0.35, Envelope Correlation Coefficient (ECC) < 0.0025 and Total Active Reflection Coefficient (TARC) < −11 dB are in acceptable limits for both symmetric and non-symmetric configurations. The proposed MIMO antenna system is suitable for 3D system-in-package, indoor localization systems, and wireless personal area network applications in industries where multiple machines are connected to a central server wirelessly through such kinds of antennas in a rich scattering 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.

Multiband MIMO Microwave and Millimeter Antenna System Employing Dual-Function Tapered Slot Structure

A single-layered multiple-input multiple-output (MIMO) antenna system is presented for future wireless devices operating at WLAN (2.45 GHz, 5.2 GHz), 4G LTE (2.6 GHz) and 5G (24 GHz, 28 GHz) bands. The design consists of a dual-band four-element monopole MIMO antenna system that covers the 2.45 GHz and 5.2 GHz bands. A decoupling mechanism is designed in the ground plane based on a tapered slot. This tapered slot has a dual function, working both as a decoupling structure ( $\lambda _{0}/4$ long) at 2.45 GHz and as a tapered slot antenna ( $3\lambda _{0}$ long) at 28 GHz when excited by a proper feeder. The proposed MIMO antenna system is designed on an RO-5880 substrate with overall dimensions of $104$ mm $\times 104$ mm $\times 0.51$ mm. The measured results show that the presented design covers two low-frequency bands (from 2.40 GHz to 5.1 GHz, from 5.1 GHz to 5.6 GHz) with a peak gain of 5 dBi and one high-frequency band (from 23 GHz to 30 GHz) with a peak gain of 11 dBi. The minimum measured isolation between the two antennas is more than 16 dB, while the maximum envelope correlation coefficient value is less than 0.16 showing good MIMO characteristics.

Novel double-side EBG based mutual coupling reduction for compact quad port UWB MIMO antenna

In this article, novel compact quad-port double-side Multiple-input-multiple- output (MIMO) antenna designed with Electromagnetic Band Gap (EBG) structure to improve isolation for Ultra Wide Band (UWB) applications. The presented MIMO configuration comprises four polygon shape radiating elements and partial slotted EBG stub ground structure. Both sides of the FR4 substrate are symmetrical, each side consisting of two radiators, and one partial ground plane is related with the other two components attached on the opposite side. The EBG decoupling structures are used on both the front and the back side of the board to diminish the correlation coupling among the radiators. The proposed MIMO antenna performance has also been studied regarding impedance bandwidth, current distribution, radiation model, envelope correlation coefficient (ECC), peak gain and TARC. The proposed MIMO antenna system has an impedance bandwidth of 3.1–11 GHz, peak gain of 2.5–6.8 dBi and less than 0.004 ECC. Furthermore, the proposed MIMO antenna shows UWB bandwidth, an almost omnidirectional radiation pattern, high isolation, uniform gain, and multi-polarization. The proposed double-sided MIMO antenna was tested in an indoor environment using NI USRP to verify performance in real time.

Investigation on decoupling of wide band wearable multiple‐input multiple‐output antenna elements using microstrip neutralization line

An investigation to enhance the decoupling between the elements of a compact wide band multiple-input multiple-output (MIMO) antenna is presented in this communication. A microstrip neutralization line (NL) is designed on the top of antenna surface to enhance the port isolation. The geometry is embedded on a jeans material to be apposite for the on-body wearable applications. The antenna covers the frequency spectra from 3.14 to 9.73 GHz (around 102.4%) and fulfills the bandwidth requirements of WiMAX (3.2-3.8 GHz), WLAN (5.15-5.35/5.72-5.85 GHz), C band downlink-uplink (3.7-4.2/5.9-6.425 GHz), downlink defense (7.2-7.7 GHz), and ITU (8-8.5 GHz) bands. The port isolation is found to be more than 32 dB over the whole application bands. The antenna is appraised in a rich scattering environment with very minimal envelope correlation coefficient (ECC < 0.12) and great amount of diversity gain (DG > 9.8). The proposed MIMO antenna system is able to achieve the channel capacity loss (CCL) of less than 0.2 BPS/Hz throughout the whole operating band. The proposed structure is etched on an area of 30 × 50 mm2. The simulated and measured performances of the proposed antenna are in well-matched state.

Compact Four-Element MIMO Antenna System for 5G Laptops

This paper presents a compact dual-band four-element multiple-input multiple-output (MIMO) antenna system for the fifth-generation (5G) laptops with a large display-to-body ratio. The four antenna elements, each being a three-dimensional inverted-F antenna (IFA) of the same structure and size, are constructed on the same T-cross-sectioned substrate, the vertical part of which is embedded in the $1\times64$ mm2 clearance area created from the upper edge of the display ground plane. They are configured into two dual-antenna units. Within each unit, the two IFAs are arranged to be skew-symmetric with respect to the display ground plane, and their short-circuit points are brought close to each other to achieve the so-called short-circuit decoupling. In addition, the two units are mirror imaged of each other with a small gap in between and are connected by two decoupling chip inductors to form a high-isolation four-element MIMO antenna system. In the operating bands of 3300–3600 and 4800–5000 MHz required by 5G, the measured isolation is larger than 10 dB, and the measured antenna efficiency is beyond 35 %, both being large enough for practical applications. In particular, the proposed MIMO antenna system has a profile height of only 1.4 mm, which is very small, making it suitable for laptops with a large display-to-body ratio.

Printed millimeter-wave MIMO-based slot antenna arrays for 5G networks

In this work, a broadband millimeter-wave (mm-wave) multiple-input–multiple-output (MIMO) antenna system for upcoming fifth generation (5G) networks is presented. The MIMO antenna system is two ports and realized using two antenna arrays, aligned in opposite directions. Each array consist of three elements in each, as each element is a simple recognized printed wide-slot antenna proximity excited by microstrip line with a widened tuning stub; manipulated for operating in the Ka-band, which includes the 28 and 38 GHz bands, as potential candidates for 5G communications. An electromagnetic band-gap (EBG) reflector is placed behind the antenna structure toward the feeding network to decrease the backward radiation and improve the front-to-back (F/B) ratio. Results show that the proposed MIMO antenna system with EBG reflector provides wideband impedance bandwidth >27 GHz (from 22.5 to >50 GHz) and good radiation characteristics with a total realized gain up to 11.5 and 10.9 dBi at the two frequencies of interest, respectively. The envelope correlation coefficient (ECC) and diversity gain (DG) were evaluated and showed good MIMO performance. These remarkable features with the benefits of design simplicity and easily expansion to large-scale antenna system make the proposed design suitable for mm-wave communications.

Two‐element printed PIFA‐MIMO antenna system for WiMAX and WLAN applications

In this study, a printed dual-band multiple-input multiple-output (MIMO) antenna is presented for Worldwide Interoperability for Microwave Access (WiMAX) and wireless local area network (WLAN) applications. Two symmetric printed inverted-F antennas (PIFAs) are considered here as radiators. One of the open-circuited radiating arms of the PIFA is loaded with a folded resonator to achieve dual-band characteristics. Two symmetric stepped `L'-shaped open ground slots have been introduced to enhance the isolation at the lower operating band. This also realises diagonal orthogonal radiation patterns of the antenna elements a results low correlation between them. Measurement reveals that the proposed MIMO antenna system has two 10 dB return loss bandwidths in the ranges of 2.6-3.08 and 5.48-6.12 GHz with isolation >21 dB over the operating bands. Respective gains are 2.5 and 3.48 dBi at the lower and upper resonant frequencies, respectively. Promising diversity performances are also investigated in terms of different MIMO parameters (total active reflection coefficient, envelope correlation coefficient, diversity gain, mean effective gain, and channel capacity loss), which are found within their acceptable range. Furthermore, the characteristics of the antenna have been investigated in the presence of a large ground plane, USB connector, and housing to ensure the applicability of the proposed antenna in handheld wireless devices.