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.
This article presents a coplanar waveguide fed global system for mobile communications band integrated ultra wide band (UWB) multiple input multiple output (MIMO) antenna with single and dual notch ...band characteristics. The novelty of the antenna lies in its design as all the unit cells of the proposed UWB MIMO antenna structure are orthogonal to each other therefore the additional isolation elements responsible for achieving high isolation are not required consequently making proposed antenna design simple and easy to fabricate. In this context, 2 MIMO systems have been designed. The first MIMO system is consisting of a dual port antenna whereas the second MIMO system is a printed quad port antenna; further single and dual notch band are achieved in the proposed multi‐port MIMO antenna. The antenna shows pattern diversity throughout the impedance bandwidth range. The gain of the antenna varies from 4 to 8.48 dBi. The 2 band notches are achieved at 4.8 and 7.7 GHz in the UWB range. The proposed antenna is fabricated and it is found measured results are in good agreement with simulated results.
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.
A highly compact and broadband antenna suitable for a prosthetic device to restore vision in the blind is presented. By embedding three straight sections of meandered microstrip patch line at the ...feed point, the proposed antenna gives three separate bands at 2.45, 4.2, and 5.8 GHz. The square patch loop is etched in the centre for miniaturisation. Three U-shaped patch stubs are utilised for frequency tuning. Three bands are merged together by adopting two square annular rings in the ground to obtain a wider bandwidth (2–8 GHz) incorporating unlicensed industrial, scientific and medical (ISM) and UWB bands.
A novel compact self‐similar fractal UWB MIMO antenna Gurjar, Rohit; Upadhyay, Dharmendra K.; Kanaujia, Binod K. ...
International journal of RF and microwave computer-aided engineering,
March 2019, 2019-03-00, 20190301, Volume:
29, Issue:
3
Journal Article
Peer reviewed
Open access
A novel compact self‐similar fractal ultra‐wideband (UWB) multiple‐input‐multiple‐output (MIMO) antenna is presented. This fractal geometry is designed by using iterated function system (IFS). ...Self‐similar fractal geometry is used here to achieve miniaturization and wideband performance. The self‐similarity dimension of proposed fractal geometry is 1.79, which is a fractional dimension. The antenna consists of two novel self‐similar fractal monopole‐antenna elements and their metallic area is minimized by 29.68% at second iteration. A ground stub of T‐shape with vertical slot enhances isolation and impedance bandwidth of proposed MIMO antenna. This antenna has a compact dimension of 24 × 32 mm2 and impedance bandwidth (S11 < −10 dB) of 9.4 GHz ranging from 3.1 to 12.5 GHz with an isolation better than 16 dB. The various diversity performance parameters are also determined. There is good agreement between measured and simulated results, which confirms that the proposed antenna is acceptable for UWB applications.
In this letter, a simple compact dual-polarized ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna is presented with the circularly polarized band for WiMAX (5.5 GHz) and WLAN (5, 5.2 ...GHz) applications. The antenna parameters such as reflection coefficient, diversity performance, gain, axial ratio, and isolation have been studied on a fabricated prototype of the proposed antenna. The 3 dB axial-ratio bandwidth (ARBW) of 34.38% along with isolation between two ports has been achieved by introducing a rectangular vertical arm (I-parameter) in the ground plane. To enhance the isolation and -10 dB impedance bandwidth, L-shaped radiators have been incorporated in the rectangular feeds. The -10 dB impedance bandwidth of the proposed antenna is 112.05% with isolation >17 dB. The envelope correlation coefficient is less than 0.01 (using S-parameter) and less than 0.15 (using far-field radiation pattern) in the entire operational bandwidth. The gain of the proposed antenna varies from 1.2 to 4.9 dBi. The performance of the proposed antenna makes it a suitable candidate for use in portable UWB applications as well as in wireless communication systems.
In this work, a novel Ultra-wideband-Multi-Input-Multi-Output Antenna Sensor (UMAS) probe is designed for the detection of the malignant cells in the breast. The Sensor probe has four radiating ...elements and it is operated within the 2.8 GHz to 20 GHz ultra-wide band range. Isolation between the radiating element is more than 20 dB. Further, three kinds of the breast phantoms (i.e. normal phantom, phantom with single and multiple tumors) are fabricated using tissue mimicking material. The electrical characteristics of the malignant cells are different from non-malignant cells of the breast. The S-parameter and Specific Absorption Rate (SAR) analysis are best approaches to detect the malignant cells in the breast. The UMAS sensing probe is embedded on the phantoms and S-parameters of the probe are recorded from the Vector Network Analyzer (VNA). Measured S-parameters of the probe for normal and malignant phantoms are differ from each other. The statistical machine learning concept of Principal Component Analysis (PCA) is also applied on the measured S-Parameters. Which exhibits clear detection of normal and malignant breast phantoms. Further verification is done by using Simulation based specific absorption rate (SAR) study of the phantom models for tumor detection. The obtained maximum SAR results are well differentiating the normal phantom.
In this article, a low‐profile bowtie shaped planar antenna loaded with long wire is designed, analyzed, and fabricated, which is fed by microstrip line and presented with and without metallic ...reflector. It consists of a planar long‐wire antenna, which is designed at 27 GHz and terminated with the input impedance of a planar bowtie shaped element supported by defected ground structure. This terminating element works as a load resistance for long wire. Furthermore, two‐element antenna arrays with proposed bowtie structure is designed, analyzed, and presented. Design equations of proposed structure are presented along with the various aspects including return loss, gain, and radiation characteristics. Proposed antenna is working within the frequency band ranging from 27 to 29 GHz and may be used for 5G wireless applications as it offers high gain within the operating frequency. Simulated results are validated by measured results of fabricated prototypes.
A hexa-band branch line coupler (BLC) and Wilkinson power divider (WPD) for long term evolution (LTE) 0.7 GHz, LTE 1.7 GHz, LTE 2.6 GHz, 3.9 GHz, public safety band (PSB) 4.9 GHz, and wireless local ...area network (WLAN) 5.8 GHz frequencies have been proposed, designed, implemented, and analyzed in this brief. To realize the proposed BLC and WPD a hexa-band quarter wave transmission line (TL) with complete derivation for a hexa-band operation has been introduced. A good performance for the BLC/WPD has been achieved over all the six bands with maximum 0.42/0.21 dB amplitude imbalance and 4.81°/0.9° phase deviation. Compared to the most of the existing BLCs/WPDs, the proposed BLC/WPD has simpler design structure and, compact size than the existing hexa and quad-band BLCs/WPDs.
A quad‐port planar multiple‐input‐multiple‐output (MIMO) antenna possessing super‐wideband (SWB) operational features and triple‐band rejection characteristics is designed. The proposed MIMO ...configuration consists of four modified‐elliptical‐self‐complementary‐antenna (MESCA) elements, which are excited by tapered co‐planar waveguide (TCPW) feed lines. A radiator‐matched complementary slot is present in the ground conductor patch of each MESCA element. The proposed MIMO antenna exhibits a bandwidth ratio of 36:1 (|S11| < −10 dB; 0.97‐35 GHz). Further, a step‐like slit‐resonator is etched in the radiator to eliminate interferences at 3.5 GHz. A hexagonal shaped complementary split ring resonator (CSRR) is also loaded on the MESCA radiator to remove interferences at 5.5 and 8.5 GHz. The MIMO antenna is fabricated on FR‐4 substrate of size 63 × 63 mm2 and experimental results are found in good agreement with the simulated results. The MIMO antenna exhibits inter‐element isolation >17 dB and envelope correlation coefficient (ECC) <0.01 at all the four ports.
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