The excessive use of digital platforms with rapidly increasing users in the wireless domain enforces communication systems to provide information with high data rates, high reliability and strong ...transmission connection quality. Wireless systems with single antenna elements are not able to accomplish the desired needs. Therefore, multiple-input multiple-output (MIMO) antennas are getting more attention in modern high-speed communication systems and play an essential part in the current generation of wireless technology. However, along with their ability to significantly increase channel capacity, it is a challenge to achieve an optimal isolation in a compact size for fifth-generation (5G) terminals. Portable devices, automobiles, handheld gadgets, smart phones, wireless sensors, radio frequency identification and other applications use MIMO antenna systems. In this review paper, the fundamentals of MIMO antennas, the performance parameters of MIMO antennas, and different design approaches and methodologies are discussed to realize the three most commonly used MIMO antennas, i.e., ultra-wideband (UWB), dual-band and circularly polarized antennas. The recent MIMO antenna design approaches with UWB, dual band and circularly polarized characteristics are compared in terms of their isolation techniques, gain, efficiency, envelope correlation coefficient (ECC) and channel capacity loss (CCL). This paper is very helpful to design suitable MIMO antennas applicable in UWB systems, satellite communication systems, GSM, Bluetooth, WiMAX, WLAN and many more. The issues with MIMO antenna systems in the indoor environment along with possible solutions to improve their performance are discussed. The paper also focuses on the applications of MIMO characteristics for future sixth-generation (6G) technology.
Abstract This paper presents a novel, dual-band, four-port multi-input–multi-output (MIMO) antenna for 28/38 GHz millimeter wave 5G wearable applications. In the proposed work, we have used a novel ...design approach to get the dual-band behavior from a MIMO design with a small footprint of 18 × 8.5 × 0.25 mm 3 . For this purpose, each MIMO element is designed as a composite form of a circular and elliptical structure connected with a narrow strip and fed by a tapered feedline. The peak realized gains and total efficiencies of the antenna, evaluated in free space, are 4.15 dBi, 7.73 dBi and 80.13%, 85.44% at 28 GHz and 38 GHz frequencies, respectively. To appraise the thorough behavior of the MIMO antenna, we have evaluated all the parameters of the antenna: Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Mean Effective Gain (MEG), Channel Capacity Loss (CCL), and Total Active Reflection Coefficient (TARC), and found them satisfactory. Channel capacity of the antenna at SNR = 20 dB is found to be 21.61 bps/Hz. For wearable applications, the proposed 4-port MIMO antenna is designed on a flexible Rogers 3003 substrate, and the performance is checked by evaluating bending analysis. The safety of the antenna is verified by analyzing the 1 g/10 g SAR at 28/38 GHz and the corresponding average SAR values are 0.11/0.08 W/kg and 0.05/0.04 W/kg, respectively. All the average SAR values for the proposed MIMO antenna are within the acceptable limits according to FCC/ICNIRP standards.
A novel design of 2 × 2 multiple‐input‐multiple‐output (MIMO) antenna is reported for ultra‐wideband applications. The neutralization line is implemented to minimize the mutual coupling between the ...radiating patches. The overall dimension of the designed antenna is 21 × 34 × 1.6 mm3. This antenna covers the measured bandwidth of 95.0% (3.52‐9.89 GHz) with better isolation (≤−22 dB) over the entire operating frequency band. The measured gain varies from 3.08 to 5.12 dBi over the entire band. The various antenna parameters such as S‐parameters, gain, efficiency, envelope correlation coefficient, mean effective gain, channel capacity loss, total active reflection coefficient, and radiation patterns are calculated and corresponding results are validated with the measured results.
In this article, a modified loop-based ingestible capsule antenna is presented with a small footprint of π × (3.5) 2 × 17 mm 3 for a wireless ultrawideband (UWB) endoscopy system. In a homogeneous ...muscle phantom, the proposed capsule antenna exhibits a frequency band ranging from 0.560 to 10.6 GHz. The in-vivo measurement is carried out by implanting the capsule antenna inside the stomach of the Wistar rat. |S 11 | results are compared when the capsule antenna is placed in a homogeneous phantom model and inside minced pork. The capsule antenna performance in the different organs of the digestive tract is studied using a 3-D human body voxel using CST Microwave studio simulator. The omnidirectional radiation patterns of the proposed design ensure that it is a suitable candidate for endoscopy communication. This antenna is applicable for ISM (Industrial, Scientific, and Medical) 0.915 GHz, WMTS (Wireless Medical Telemetry Services) 1.4 GHz, ISM 2.45 GHz, and 3.1-10.6 GHz (UWB) frequency range.
In this article, a microstrip line fed 2‐port circularly polarized multiple‐input‐multiple‐output (MIMO) antenna is designed and fabricated. A novel ground structure and radiating patches are used to ...achieve the circularly polarized radiated field by the MIMO antenna. To improve the isolation between two ports, a meandered U‐shaped narrow metallic strip is placed between the asymmetric Z‐shaped radiating elements. The proposed MIMO design demonstrates the impedance bandwidth (S11 ≤ −10 dB) of 90.94% (3.04‐8.11 GHz). The axial ratio bandwidth ≤3 dB is found to be 32.10% (4.42‐6.11 GHz). The diversity parameters such as envelope correlation coefficient, diversity gain, mean effective gain, total active reflection coefficient and channel capacity loss are also calculated to make the proposed design more reliable for 5G applications. This antenna is made compact and small which carries the dimension 24 × 24 × 1.6 mm3. The entire investigation is first modeled using the simulation software CST Microwave Studio and then verified with the measured results.
This paper proposes a dual-band two-port multiple-input-multiple-output (MIMO) antenna system for intra-heart communication for future dual-chamber leadless cardiac transcatheter pacing (TCP) systems ...on Internet of things (IoT) environment. The MIMO antenna is designed and miniaturized using a fractal approach with Minkowski island geometry. The fractal-based antenna design has a footprint of 3 mm × 6.6 mm × 0.254 mm, with an inter-element isolation of 24 dB and 18 dB in the 2.45 GHz and 5.8 GHz (ISM) bands, respectively. This is the first time a dual-chamber pacing system is proposed using a dual-band two-port MIMO antenna integrated TCP in the 2.45 GHz/5.8 GHz bands by placing two leadless TCP systems at an 80 mm distance and analyzing data transfer between them with different cases of the cardiac cycle. The proposed MIMO communication system can withstand more losses than the other reported works. Patient safety is also ensured by analyzing the specific absorption rate of the antenna system, which is within the range defined by the Federal Communications Commission.
A compact dual band 2 × 2 multiple-input-multiple-output (MIMO) antenna with dimension 46 × 30 × 1.6 mm
3
is reported. The designed CPW-fed MIMO antenna structure consists of swastika shaped slot in ...the rectangular patch. A T-shaped narrow conducting strip is used in ground plane to improve the isolation between the two radiating elements. The measured lower and upper frequency bandwidths are respectively 64.96% (1.85–3.63 GHz) and 44.36% (5.07–7.96 GHz), along with the corresponding isolation
≤
-
17.21 dB and
≤
-
22.42 dB. The measured realized gain changes from 1.14 to 4.12 dBi (lower band) and from 1.42 to 4.78 dBi (upper band) and the radiation efficiency is found over 72% for both the frequency bands. The antenna diversity parameters alongwith the radiation patterns are also investigated. Initially, the antenna is modelled using CST Microwave studio and the optimized design is fabricated and measured for validity of results.
A miniaturized half cut coalesced kite shaped printed antenna is presented for the ultrawide band (UWB) characteristics. The proposed design bears a compact and small physical dimension of 25 (L) × 9 ...(W) × 1.6 (h) mm3. This structure produces higher impedance bandwidth as compared to the corresponding full structure of the antenna design. The variation of ground plane dimension is studied to get the optimized results of the antenna. The measured impedance bandwidth (return loss <10 dB) of the proposed antenna is found to be 16.12 GHz in the frequency range 1.02 to 17.14 GHz. The average measured gain for this design is 3.12 dBi for the entire band of operation. The far field radiation patterns are also presented at 1.18, 3.1, 6.85, and 10.6 GHz. The antenna performances are first analyzed by the CST Microwave Studio, the simulation software based on finite integration technology (FIT) and then the optimized structure is fabricated for the measurements. The proposed design structure reveals the recent state of art by using the half cut technique which not only miniaturizes the size but also covers the whole UWB range to be used for many wireless systems.
In this paper, a scarecrow-shaped ultrawideband (UWB) antenna is presented using CPW and microstrip line feeding. The physical dimensions of the proposed antennas are
25
×
20
×
1.6
mm
3
, in which ...the modification in the ground is made by etching two half-circle and square slots symmetrical with respect to center feed line. The measured impedance bandwidth (return loss
<
10
dB
) obtained for CPW-fed antenna is 147.13% (2.51–16.48 GHz), and for microstrip-line-fed antenna it is 139.88% (2.86–16.17 GHz). Various antenna parameters for both the designs are calculated, such as gain, radiation pattern and group delay which are quite acceptable for UWB applications. The proposed designs are first simulated by the CST Microwave Studio, and optimized designs are fabricated. The simulated and measured results are compared for the validation of the design.
In this paper, two different radiating structures fed with modified L-probe, are reported using a circuit theory concept. The proposed antennas are operating in wireless local area network (WLAN) and ...universal mobile telecommunications system (UMTS) frequency bands. In the first design, an E-shaped patch is studied to increase the bandwidth. It is observed that the bandwidth is directly proportional to notch dimensions. In the second design, E-shaped patch is modified to reduce the antenna size up to 30% with high bandwidth. In the first design, measured bandwidth and gain achieved are 32.68% (1.92–2.67 GHz) and 8.43 dBi while in second design it is 34.19% (1.94–2.74 GHz) and 8.39 dBi, respectively. Radiation patterns for both the antennas are symmetrical and broadside in nature. The proposed antennas are fabricated and measured results compare well with the theoretical and simulated results.
