Multiple-input Multiple-output Antenna Research Articles

A wideband self‐decoupled multi‐input multi‐output antenna with a high isolation

A wideband MIMO antenna, which consists of two adjacent antenna elements with a very close distance (2 mm or 0.026λ), is suggested to achieve a good isolation by the principle of common mode (CM, in-phase signals) and differential mode (DM, out-of-phase signals) cancelation without using any additional decoupling structure in this article. Compared with its reference design, the measured results demonstrate that the isolation of proposed design can be improved to better than 20 dB in a wider bandwidth of 3.2–5.9 GHz (59%), with S11 and S22 < −10 dB. The experimental efficiency and envelope correlation coefficients are larger than 78% and <0.04 for the proposed design, respectively. The proposed multiple-input multiple-output (MIMO) antenna array, with good isolation and diversity performance, exhibits broad application prospects in the tightly arranged MIMO antennas of 5G mobile devices.

Realization of miniaturized Triple-Band Four-Port stacked MIMO antenna for WLAN applications at 2.9/5.0/5.9 GHz bands

A compact four-port multiple-input multiple-output (MIMO) antenna is realized. The proposed antenna is designed as a stacked microstrip patch antenna that offers triple-band performance at 2.9 GHz, 5.0 GHz, and 5.9 GHz. The proposed antenna is a suitable candidate for WLAN applications covering three distinct bands of IEEE 802.11 protocols. All four ports of the designed antenna are uncorrelated, and a very low mutual coupling of less than –23 dB is obtained. The dimensions of the four-element MIMO are 0.4λ0 × 0.4λ0 × 0.03λ0. The step-by-step evaluation of the proposed antenna is presented in this work. A prototype of the proposed antenna is fabricated, and experimental results are compared with the simulated results. Both simulated and experimental results are found in close agreement.

A novel wearable free‐wideband antenna circularly polarized suited for biotelemetric devices with multiple‐input multiple‐output and high data rate capacity

A small circularly polarized multiple-input multiple-output (MIMO) antenna is demonstrated here as a biometric gadget for consumers. In this article, the authors introduce a structure for antennas that consists of four essential parts that are orthogonally arranged opposite each other. The transmitted signal has around 10 db wideband response at 2.22 GHz, referred to as fractional band-widths (FBW) which is 91.08 achieved when operated in free space. Also included is a 10-db transmitter with a 2.44-GHz band-width, a FBW of 92.56%, and it can be used on wearables on human bodies. The authors have therefore calculated frequency ranges that cover the most important and unlicensed free of cost open-source band-width of 2.4 to 2.48 GHz that is also known as ISM band (industrial, scientific, and medical) range. When operated in free space and in human body proximity of 5 MM, the antenna also operates at 1.3 GHz, which is approximately 54.16% fractional band-width, as well as 1.04 GHz, which is approximately 43.33% fractional band-width. An antenna that is finalized in free-space (or within 5 mm of a human body) has an optimum envelop correlation coefficient (ECC) beneath 0.22 (0.24), and an optimal gain of about 3 dB.

Dual-band reconfigurable EBG loaded circular patch MIMO antenna using defected ground structure (DGS) and PIN diode integrated branch-lines (BLs)

In this work, a reconfigurable dual-band multiple-input–multiple-output (MIMO) antenna (RDMA) for the fifth generation (5G) 3.5 GHz and industrial, scientific and medical (ISM) 5.2 GHz has been reported. The reported antenna uses the partial ground plane defected ground structure (PGP-DGS) technique and the integration of the pin diode integrated branch lines (BLs) to obtain dual-band operation. Also, the intermediate structure, without DGS operates in wideband to narrowband reconfigurable mode. The operating frequency of the antenna can be tuned to other frequencies by changing the DGS and BLs design attributes. A novel mushroom inspired dual-band electronics bandgap structure is developed and characterized using a dispersion diagram. The proposed EBG is then placed between RDMA to obtain isolation better than −25 dB between closely packed (at λ5G/17.14) antenna elements. The proposed antenna has an acceptable realized gain above 2.5 dBi and a stable end-fire radiation pattern with the main lobe at −45∘.

Design of a Millimeter-Wave MIMO Antenna Array for 5G Communication Terminals.

This paper presents a design of multiple input multiple output (MIMO) antenna array for 5G millimeter-wave (mm-wave) communication systems. The proposed MIMO configuration consists of a two antenna arrays combination. Each antenna array consists of four elements which are arranged in an even manner, while two arrays are then assembled with a 90-degree shift with respect to each other. The substrate used is a 0.254 mm thick Rogers RT5880 with a dielectric constant of 2.2 and loss tangent of 0.0009, correspondingly. The proposed MIMO antenna array covers the 37 GHz frequency band, dedicated for 5G millimeter-wave communication applications. The proposed antenna element yields a gain of 6.84 dB, which is enhanced up to 12.8 dB by adopting a four elements array configuration. The proposed MIMO antenna array performance metrics, such as envelope correlation coefficient (ECC) and diversity gain (DG), are observed, which are found to be under the standard threshold. More than 85% of the radiation efficiency of the proposed MIMO antenna array is observed to be within the desired operating frequency band. All the proposed designs are simulated in computer simulation technology (CST) software. Furthermore, the measurements are carried out for the proposed MIMO antenna array, where a good agreement with simulated results is observed. Thus, the proposed design can be a potential candidate for 5G millimeter-wave communication systems.

Performance of Dense Wireless Networks in 5G and beyond Using Stochastic Geometry

Device density in cellular networks is expected to increase considerably in the near future. Accordingly, the access point (AP) will be equipped with massive multiple-input multiple-output (mMIMO) antennas, using collimated millimeter-wave (mmW) and sub-THz communications, and increasing the bandwidth to accommodate the growing data rate demands. In this scenario, interference plays a critical role and, if not characterized and mitigated properly, might limit the performances of the network. In this context, this paper derives the statistical properties of the aggregated interference power for a cellular network equipping a mMIMO cylindrical array. The proposed statistical model considers the link blockage and other network parameters such as antenna configuration and device density. The findings show that the characteristic function (CF) of the aggregated interference power can be regarded as a weighted mixture of two alpha-stable distributions. Furthermore, by analyzing the service probability, it is found that there is an optimal configuration of the array depending on the AP height and device density. The proposed statistical model can be part of the design of dense networks providing valuable insights for optimal network deployment and resource management and scheduling.

Metasurface Superstrate-based MIMO Patch Antennas with Reduced Mutual Coupling for 5G Communications

Multiple-input multiple-output (MIMO) systems have several advantages, such as providing high capacity, spatial diversity, etc. MIMO antennas suffer with high mutual coupling (m-coupling) between the ports. In this paper, the metasurface with negative permeability (MNG) is designed and utilized for m-coupling reduction of a two-port rectangular microstrip MIMO antenna (Antenna 1). Two metasurface superstrate-based MIMO antennas with reduced m-coupling for fifth generation (5G) are proposed. The first design (Antenna 2) is constructed using a single metasurface superstrate suspended above the two-port MIMO microstrip antenna. The second design (Antenna 3) is constructed using a double metasurface superstrate layers suspended above the two-port MIMO microstrip antenna. Both metasurface-based MIMO antennas achieve significant m-coupling reduction over the entire bandwidth. The edge-to-edge separation between the two patches is 0.29λ0. The proposed Antenna 3 obtains the reduced m-coupling of −44 dB along with the wide bandwidth of 5.92−6.2 GHz and a maximum gain of 6.79 dB. The proposed antennas are suitable for extended sub-6 GHz 5G applications with the operating frequency band of 5.9–6.1 GHz.

A Compact Planar Monopole UWB MIMO Antenna Design with Increased Isolation for Diversity Applications

A compact planar multiple input multiple output (MIMO) antenna with four elements spanning the ultra-wideband (UWB) is proposed for diversity applications. The unit cells are positioned orthogonally to lower the mutual coupling by replicating the single antenna three times. A 35 × 35 × 1.6 mm3 UWB MIMO antenna is provided with a 50-Ω impedance microstrip line on a 1.6-mm thick FR4 substrate. In the radiator and ground plane, some modifications are made to achieve the operating limits of this antenna between the frequencies of 3.1-10.6 GHz, thereby covering the entire frequency spectrum of the UWB with compact size. We conclude from the calculated results that the proposed antenna has high performance characteristics appropriate for UWB wireless indoor communication and diversity applications with compact size.

Optimized Super-Wideband MIMO Antenna with High Isolation for IoT Applications.

A compact, low profile, multiple-input–multiple-output (MIMO) diversity antenna with super-wideband (SWB) characteristics has been proposed. The proposed antenna comprises four symmetric monopole-radiating elements printed on low-cost FR4 substrate with the slotted ground plane. The single antenna of a monopole structure and a quad-port MIMO antenna, with the dimensions of 30 × 20 mm2 and 60 × 55 mm2, respectively, are ideal for IoT and high-speed data applications. The proposed MIMO antenna has a high diversity gain and low envelope correlation coefficient (ECC) within the frequency range. Simulated results demonstrate the performance of the MIMO-SWB antenna, which operates from 2.3 to 23 GHz, with a high isolation level over 20 dB in the achieved frequency band. Moreover, the proposed MIMO antenna has been investigated with mirror fashion and orthogonal structure. Both structures provide similar results except for mutual coupling performance. The orthogonal adjustment for high isolation achieves better results with the proposed model. Further, the prototype of the proposed antenna is fabricated and measured effectively. Simulated and measured results show good agreement for super-wideband applications.

Leveraging frequency agility of an MIMO antenna cluster with a transmitter IC

AbstractThis paper presents the prototype demonstration where an integrated transmitter circuit drives a mobile handset terminal antenna in order to provide frequency tunability and multiple input multiple output (MIMO) operation across the 0.5–4.5 GHz frequency range. The transmitter implementation incorporates on-chip weighted signal generation, i.e. amplitude and phase scaling to provide sufficient MIMO performance in the low band (700–960 MHz) and in the high band (1.5–4.5 GHz). In the transmitter, two antenna elements are used for MIMO operation in the low band and another two in the high band. The transmitter integrated circuit (IC) is fabricated in a 28 nm bulk CMOS technology with an active on-chip area of 0.2 mm$^2$. A custom antenna measurement procedure is proposed here in order to support and verify active antenna measurements with transmitter IC. A measurement procedure for the transmitter system comprising the transmitter IC and four antenna clusters is developed and discussed in comparison with traditional passive antenna measurements. The measurement results demonstrate that the transmitter IC driving the antenna clusters provides total antenna efficiency of $-6.5$ dB to $-1.5$ dB, and envelope correlation coefficient below 0.4 across the designated frequency bands. The results indicate that the implemented transmitter IC successfully tunes frequency response of the antenna clusters, and enhances the MIMO operation of such mobile antennas.

Design of a tri‐band multiple input multiple output antenna with high isolation for 5G applications

A novel tri-band multiple input multiple output (MIMO) antenna with high-isolation is proposed in this article. The proposed tri-band MIMO antenna consists of two tri-band monopole antennas placed symmetrically. Due to the ground surface wave, a defected ground structure (DGS) is etched to extend the ground surface current and reduce the port-to-port coupling. Then two ground branches are loaded on the ground plane as a reflector that inhibit and reflect the coupling between the two parasitic elements. In order to suppress the space surface waves, a novel non-connected neutralization structure is loaded on the microstrip line of two monopole antenna elements. As a result, the quite good isolation and impedance matching are obtained by generating different resonance at different frequency of the structure. Finally, the proposed tri-band MIMO antenna with the decoupling structure achieves 5G tri-band of 2.5–2.7, 3.26–3.83, and 4.73–4.97 GHz (S11&S22 < −10 dB, S12 & S21 < −25 dB). The results show that the proposed tri-band MIMO antenna can cover the whole 5G bands (sub-6 GHz) and has good isolation characteristic, which can well meet the 5G applications.

MIMO antenna performance with isolator

AbstractIn this article, the effect of an isolator in a multiple‐input multiple‐output (MIMO) antenna is analyzed in terms of its efficiency and isolation. An isolator is frequently utilized in MIMO antennas; however, the use of an isolator can aggravate the bandwidth or efficiency performance even though its isolation performance is improved. To develop a way of applying an isolator without sacrificing the bandwidth or efficiency performance, it is important to note that the characteristic modes excited by the MIMO antenna are related to the performance of the isolator. Two MIMO antenna systems using different ground characteristic modes are implemented to analyze the effect of the isolator. Via the isolator, both MIMO antennas achieved improved isolation, but the reference antenna underwent severe bandwidth degradation and efficiency degradation (from 31.81% to 16.69%), whereas the proposed antenna had relatively smaller reductions in bandwidth and efficiency (from 53.14% to 46.87%).

Dual-Band Folded Monopole MIMO Antennas with Enhanced Isolation

In this paper, a compact dual-band multiple-input multiple-output (MIMO) diversity antenna is proposed. Each of the two MIMO antennas consists of two folded strips working as radiating elements that are fed by a microstrip line. The antennas operate in three WLAN bands: ISM 2.45 GHz, 5.25 GHz, and ISM 5.775 GHz. To improve the isolation at WLAN (2.4–2.48 GHz), two L-shaped slots are etched in the ground plane while a U-shaped slot is cut in the ground plane to enhance isolation at WLAN (5.15–5.35 GHz and 5.725–5.825 GHz). Three slots on the substrate between radiating patches are also employed for an extra reduction in the mutual coupling at 2.45 GHz. The antenna performance was examined by simulation employing CST Microwave Studio Software. The proposed antenna offers minimum isolation of more than 19.5 dB, a low envelope correlation coefficient (ECC) of less than 0.0016, and good radiation efficiency (∼∼80%) through the operating frequency bands. The antenna is compact, thin, and suitable for portable devices.

A compact two elements MIMO antenna for 5G communication

This study presents a simple, miniaturized, and low-profile multiple-input multiple-output (MIMO) antenna operating at 29 GHz with reduced mutual coupling between the antenna elements for futuristic 5G communication. The proposed design employs two radiating elements with slits in the radiators to produce high isolation among the antenna radiators. The MIMO antenna maintains a compact structure of 11.4 × 5.3 mm2, which is the smallest size compared to previous 5G antennas. Roger’s 4350B laminate was employed as a substrate material. At 29 GHz, low mutual coupling of − 36 dB, low envelope correlation coefficient (ECC < 0.001), and high diversity gain (DG > 9.8 dB) are achieved. The proposed design is examined in terms of the S-parameters, diversity gain, radiation pattern, and envelope correlation. Compared to the straight antenna element, an improvement of − 20 dB is observed in the isolation for both the simulated and measured results.

Design of Low-Profile Compact MIMO Antenna on a Single Radiating Patch Using Simple and Systematic Characteristic Modes Method

This article designs a class of low-profile compact multiple-input–multiple-output (MIMO) antennas on a single radiating patch using simple and systematic characteristic modes (CMs) method. Rather than using conventional method of radiation pattern and polarization diversities, this work demonstrates that by taking advantage of a proper superposition of some even/odd modes, it is able to generate similar radiation pattern and polarization no matter which port is excited. It is also found that port isolation and impedance matching are dependent on not only operating modes but also input couplings. The proposed CMs method consists of three main steps. First, adjust desired even and odd modes to be equal in resonant frequency (ResF). Second, suppress unwanted modes without affecting desired ones. Lastly, determine feeding positions to obtain proper input couplings. In this way, satisfactory port isolation and impedance matching could be achieved simultaneously and quickly, getting rid of complicated decoupling structures and time-consuming optimization. To exemplify how the proposed CMs method works, two MIMO antennas are successfully designed by just using simple slots and shorting pins. A prototype for the proposed four-port MIMO antenna is fabricated and measured for validation.

Minimally Coupled Two-Element MIMO Antenna with Dual Band (28/38 GHz) for 5G Wireless Communications

This paper presents a dual-band 28/38 GHz two elements multiple-input multiple-output (MIMO) antenna with high isolation for 5G applications. The suggested antenna is a monopole with rectangular and triangle stubs added to the patch and a partial ground plane to achieve the dual band’s behavior. Two elements of the suggested antenna are combined and placed orthogonally to achieve the high isolation features of the MIMO configuration at 28/38 GHz. The MIMO configuration has a size of 27.65 times 12 times 0.273 mm3. The suggested MIMO prototype is fabricated and tested. The tested results achieved dual frequency bands with S11 lower than − 10 dB within two frequency bands (26–30 GHz and 36–41.5 GHz) and S21 lower than − 20 dB through the two operated bands. The suggested antenna has semi-omnidirectional radiation patterns in both planes. As well, its measured peak gain is 5.2 dBi and 5.3 dBi at the two operated frequency bands, respectively. Also, the MIMO parameters are extracted to validate the simulated results. The simulated and tested results have a good matching within the two operating bands which suggests the proposed structure be utilized in 5G communications.

Phase Transition Analysis for Covariance-Based Massive Random Access With Massive MIMO

This paper considers a massive random access problem in which a large number of sporadically active devices wish to communicate with a base station (BS) equipped with massive multiple-input multiple-output (MIMO) antennas. Each device is preassigned a unique signature sequence, and the BS identifies the active devices by detecting which sequences are transmitted. This device activity detection problem can be formulated as a maximum likelihood estimation (MLE) problem for which the sample covariance matrix of the received signal is a sufficient statistic. The goal of this paper is to characterize the feasible set of problem parameters under which this covariance based approach is able to successfully recover the device activities in the massive MIMO regime. Through an analysis of the asymptotic behaviors of MLE via its associated Fisher information matrix, this paper derives a necessary and sufficient condition on the Fisher information matrix to ensure a vanishing probability of detection error as the number of antennas goes to infinity, based on which a numerical phase transition analysis is obtained. This condition is also examined from a perspective of covariance matching, which relates the phase transition analysis to a recently derived scaling law. Further, we provide a characterization of the distribution of the estimation error in MLE, based on which the error probabilities in device activity detection can be accurately predicted. Finally, this paper studies a random access scheme with joint device activity and data detection and analyzes its performance in a similar way.

Low-SAR Four-Antenna MIMO Array for 5G Mobile Phones Based on the Theory of Characteristic Modes of Composite PEC-Lossy Dielectric Structures

A low-specific absorption rate (SAR) four-antenna multiple-input–multiple-output (MIMO) antenna array is designed for fifth-generation (5G) mobile phones based on the theory of characteristic modes (TCM) of the composite perfect electric conductor (PEC) and lossy dielectric structures. First, the TCM of composite PEC-lossy dielectric structures is reviewed briefly. Then, the application of the theory for low-SAR antenna design is demonstrated through a four-antenna MIMO antenna array. Finally, the proposed MIMO array is fabricated, and its performance is measured. Its −10 dB impedance bandwidth can cover the desired frequency band from 3.4 to 3.6 GHz. The isolations between different antenna elements are higher than 15.4 dB. Their total efficiencies range from 81.3% to 89.9%. The envelope correlation coefficient (ECC) is lower than 0.07. The 10 g spatial-average body SAR corresponding to the situation that four antennas simultaneously radiate is 0.47 W/kg. Compared with the state-of-the-art 5G MIMO antenna arrays, the proposed MIMO antenna array has the lowest peak SAR value, satisfactory efficiency, isolation, and ECC. This article provides a general methodology for the design of low-SAR mobile phone antennas.

Optimum polarization configuration of planar circular patch MIMO antenna

Multiple Input Multiple Output (MIMO) is a key technology that plays an important role in achieving the 5G requirement due to its capability to increase channel capacity. However, the increase of channel capacity is influenced by several aspects such as mutual coupling. Many methods are done to decrease the mutual coupling effect such as polarization arrangement of the MIMO antennas. This study on the polarization arrangement of a circular patch MIMO antenna at 3.5 GHz was performed. Four elements of the MIMO antenna are arranged with several polarization configurations both in Co-Polarization and Cross-Polarization. Both simulation and measurement results showed that MIMO with Co-Polarization has a slightly wider bandwidth equal to 295.25 MHz compared to Cross-Polarization with a bandwidth of 274.63 MHz, due to better return loss performed by the former. However, from the mutual coupling perspective, it is observed that MIMO with Cross-Polarization can reduce the mutual coupling from -17.6676dB into -22.462 dB compared to Co-Polarization with the same element distance.

New MIMO Antenna with Filtration for the Future Multiuser Systems in Satellite Communications

This paper emphasizes the function of the split ring resonator (SRR) within the design of ultra-wideband (UWB) antennas. We presented an antenna that belongs to the category of UWB antenna with two rejected bands based on square SRR. At first, we presented a UWB antenna. This antenna is designed to operate in the band 2.3–11.5 GHz. Then, with the integration of two SRR cells, we were capable of filtering the bands 3.7–3.9 GHz and 8.7–8.9 GHz without losing the UWB characteristics outside these rejected bands. Next, to ensure the proper performance of the MIMO system, we studied the use of metamaterials in the design of MIMO (Multiple-Input Multiple-Output) antennas for miniaturization and antenna performance.