Good Diversity Performance Research Articles

A crossed-polarized four port MIMO antenna for UWB communication

This paper presents a compact, crossed-polarized, ultra-wideband (UWB) four-ports multiple-input-multiple-output (MIMO) printed antenna. The proposed antenna is constructed from four microstrip circular patch elements fed by a 50-Ω microstrip line. Two metamaterial cell elements, in the form of a rectangular concentric double split ring resonator (SRR), are placed at the upper plane of the substrates for bandwidth improvement and isolation enhancement. The ultra-wideband frequency response is achieved using a defective ground plane. Surface current flow between the antenna's four elements is limited to ensure maximum isolation. The four-port MIMO system is designed with orthogonal antenna elements orientation on an FR4 substrate with a loss tangent of 0.02 and an overall size of 30 mm × 30 mm × 1.6 mm. Such orientation resulted in less than −17dB port-to-port isolation and an impedance bandwidth of 148% (3.1–12 GHz). The proposed UWB-MIMO antenna achieved a maximum realized gain of 6.2dBi with an efficiency of 87%. The measured and simulated results are in good agreement over the operating frequency band (3.1–12 GHz). The results also provide overall good diversity performance with the TARC < −10 dB, ECC < 0.001, DG > 9.9, MEG < −3 dB and CCL <0.1. The proposed antenna is well-suited for applications in WLAN, WIMAX and GPRs.

Miniaturized Folded-Slot CubeSat MIMO Antenna Design with Pattern Diversity.

In this paper, a folded slot-based multiple-input–multiple-output (MIMO) antenna design for Cube Satellite (CubeSat) applications is presented for the ultra-high frequency (UHF) band. A unique combination of a reactively loaded meandered slot with a folded structure is presented to achieve the antenna’s miniaturization. The proposed antenna is able to operate over a wide frequency band from 430~510 MHz. Moreover, pattern diversity is achieved by the antenna’s element placement, resulting in good MIMO diversity performance. The four elements are placed on one Unit (1U) for CubeSat dimensions of 100 mm × 100 mm × 100 mm. The miniaturized antenna design with pattern diversity over a wide operating band is well suited for small satellite applications, particularly CubeSats in the UHF band.

Design of Compact Planar Monopole UWB MIMO Antenna with Four Orthogonal Elements and Tapered Fed Configuration for Wireless Diversity Applications

In this paper, we introduce a four-port self-isolated UWB MIMO antenna for diversity applications. First, we have developed a basic radiating element of the proposed antenna in four stages of design, where patches of geometrically different shapes were added at each stage to arrive at the final radiator form. The antenna was designed on an FR-4 substrate with a compact size of 28 × 28 × 1.6 mm3. A tapered microstrip feeding was employed to enhance the antenna’s impedance matching. An orthogonal arrangement of the four radiators was adopted to mitigate the mutual coupling between them, avoiding the use of a separate isolation structure. A prototype was built and measured with a close agreement between the experimental and simulated results. The MIMO antenna performed well in the entire frequency spectrum of 3.1–10.6 GHz, with an isolation better than 20 dB. The measured envelope correlation coefficient (ECC) was less than 0.001, the diversity gain (DG) was greater than 0.99 dB, and the total active reflection coefficient (TARC) was less than −10 dB. The performance of the proposed antenna design was compared with existing designs. The comparison showed that the proposed quad-element UWB MIMO array is compact, has good isolation and diversity performance compared to existing designs, and is well-suited for wireless diversity applications.

Dual-Band Multiple-Element MIMO Antenna System for Next-Generation Smartphones

This work presents a cost-effective multiple-element multiple-input multiple-output (MIMO) antenna system for next-generation smartphones. The proposed antenna system is developed on a 0.8 mm thin FR-4 substrate with a relative permittivity of 4.4, which consists of one main board and two sideboards. The dimensions of the main board and the two side boards are 150 × 75 mm2 and 150 × 6 mm2, respectively. The radiating elements are printed on the sideboards to provide space for other radio frequency (RF) components to be embedded on the main board. The proposed antenna resonates at two distinct allotted 5G bands, i.e., 3.5 GHz and 5.4 GHz, with impedance bandwidths of 200 MHz and 700 MHz, respectively. The isolation between the antenna elements is noted to be &gt;18 dB and &gt;12 dB for the 3.5 GHz and 5.4 GHz frequency bands. In addition, the proposed MIMO antenna provides pattern and spatial diversity characteristics in both bands with good gain and efficiency. Furthermore, the MIMO parameters such as envelope correlation coefficient (ECC), mean effective gain (MEG), and channel capacity (CC) are calculated, and it is observed that the MIMO antenna offers good diversity performance for the bands of interest. A prototype is fabricated and measured to verify the numerical data. The simulated results were discovered to be in excellent agreement with the measured results. It is also observed that the proposed MIMO antenna system holds promising features, and can be utilized for future generations of smartphones.

Miniaturization and performance enhancement of super wide band four element MIMO antenna using DNG metamaterial for THz applications

A compact semi-hexagonal-shaped MIMO antenna loaded with a planar SRR (split-ring resonator) structure is presented for Terahertz applications. The single radiating element consists of a semi-hexagonal shape metallic patch loaded with SRR-CC (Split ring Resonator-Connected C shape) metamaterial unit cell to enhance the impedance bandwidth as well as gain of the proposed antenna. The proposed antenna element can be easily extended into two-port and four-port MIMO antenna configurations. Four radiating elements of the proposed antenna are printed on 122.4*122.4 μm2 quartz substrate having a thickness of 10 μm. The radiating elements are placed orthogonally to achieve high isolation and miniaturization in the MIMO system. The proposed antenna exhibits super-wide impedance bandwidth (S11 ≤ − 10 dB) in the range of 0.9–10.1 THz (with fractional bandwidth of 168% at f0 = 5.5 THz) while isolation of antenna is more than 20 dB in the whole operating band. The peak gain of the antenna is 7.51 dBi with more than 95% radiation efficiency in the entire band. The stable radiation pattern, high gain, high radiation efficiency, and good diversity performance of the proposed antenna make it suitable for many THz applications such as breast cancer detection, sugar measurement, drug detection.

Design of a Compact UWB-MIMO Antenna with Isolation Enhancement through Extended Elliptical Ground Plane

This paper deals with the design of a Multiple Input Multiple Output (MIMO) antenna for UWB applications. It is composed of two identical radiating elements (parallel monopoles) symmetrically arranged on a FR-4 substrate. The monopoles are closely spaced (about 0.2 Lambda, center to center). A decoupling mechanism based on vertical extension of the Ground plane with elliptical edges (stub) allows to achieve high isolation (&gt;20 dB). Further, the designed system presents good diversity performance, as the obtained Envelope Correlation Coefficient is less than 0.01. The antenna array is compact (36x30 mm2), with ultra-wide operating frequency range (2.6 to 10.8 GHz). Simulations and measurements demonstrate good agreement. The obtained results make the proposed structure a good candidate for any UWB applications and modern wireless communications systems thanks to its wide frequency band, compactness and performance.

Asymmetrical fed Calendula flower-shaped four-port 5G-NR band (n77, n78, and n79) MIMO antenna with high diversity performance

AbstractThis research reports a four-port multiple-input-multiple-output (MIMO) antenna designed for 5G-NR band applications including n77: 3.30–4.20 GHz, n78: 3.30–3.80 GHz, and n79: 4.40–5.00 GHz. The proposed design is analyzed in two parts, one single-element asymmetrical fed Calendula flower-shaped antenna and the other four-port modified MIMO antenna with the connected ground. The evolution of the MIMO antenna is studied based on the characteristics and optimized single-element antenna. The measured 5G-NR bandwidth offers a very high matching of impedance for MIMO configuration and higher isolation in the same band. The MIMO antenna offers an average peak gain of 3.51 dBi with a radiation efficiency of more than 90%. The radiation patterns plotted at 3.51, 4.00, 4.50, and 5.00 GHz match with almost omni-directional and dipole patterns in H- and E-radiating planes respectively. The MIMO antenna also records good diversity performance (ECC, DG, CCL, MEG, and TARC) in n77, n78, and n79 5G bands.

Eight‐element fifth‐generation multiple‐input multiple‐output antenna designed by modal currents cancelation

An antenna decoupling method based on modal control is proposed in this paper. Different from the previous characteristic mode decoupling methods, which excite one of the characteristic modes from each port, a pair of decoupling modes is excited simultaneously at each port. To validate our method, a head-to-head antenna pair is analyzed and designed. According to the characteristic mode analysis, an inductor-loaded coupled sheet is introduced for the head-to-head antenna pair. Thus, the resonant frequencies of decoupling modes can be tuned individually. To further demonstrate the flexibility of our design, an eight-element multiple-input multiple-output (MIMO) antenna composed of two integrated four-element blocks is designed, fabricated, and measured. The proposed antennas show good impedance matching, isolation, and diversity performance varying from 3.35 to 3.71 GHz. Both simulated and measured results show the 8 × 8 MIMO system can achieve isolations of better than 11.5 dB and envelope correlation coefficients of less than 0.2 of each port.

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.

Compact ultra-wideband pattern diversity antenna for body-centric communications

AbstractThis paper presents a pattern diversity UWB antenna for Wireless Body Area Network (WBAN) communications. Pattern diversity antenna comprises two antenna elements with directional and omnidirectional patterns suitable for off-body and on-body communications respectively. Several broad-banding techniques such as Co-Planar waveguide, parasitic patches, and cavity resonant techniques are incorporated in microstrip antenna to achieve an ultra-wideband of 7.5 GHz (3.1 to 10.6 GHz) with a directional pattern. Monopole radiator topology is utilized to achieve a UWB frequency range of 2.6–10.6 GHz with an omnidirectional pattern. Pattern diversity is achieved using an orthogonal arrangement of the antenna elements in a compact size of 40 mm × 34 mm, maintaining the isolation &gt;20 dB between the antennas. Gain varies from 2.2 to 4.6 dBi and 2.5 to 7.5 dBi for omnidirectional and directional antenna respectively. The simulated radiation efficiency for the directional antenna and the omnidirectional antenna are 74–86% and 52–66.5% respectively. The proposed design provides a good diversity performance in the entire UWB bandwidth with ECC&lt;0.1 and a diversity gain of approximately 10 dB. SAR impact evaluated under various conditions is found to be &lt;1.6 W/Kg for 1 gram of tissue.

A Four-Port CSRR-Loaded Dual-Band MIMO Antenna With Suppressed Higher Order Modes

In this paper, we propose a compact four-port dual-band MIMO antenna with suppressed higher order modes (HOMs). First, complementary split ring resonator (CSRR) loading is used on a square microstrip antenna to achieve simultaneous miniaturization and dual-band response. Next, the HOMs in the proposed CSRR loaded MIMO configuration are analysed using equivalent circuit model as well as surface current distribution plots. By placing a single shorting post close to antenna center line, these HOMs of the four-port dual-band MIMO antenna are then suppressed, while maintaining satisfactory mutual coupling (<−11 dB) and impedance matching (<−15 dB) performance in the operating band. Furthermore, simulated and measured values of total active reflection coefficient ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TARC</i> ), envelop correlation coefficient ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ECC</i> ) and channel capacity loss ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CCL</i> ) are within the desired levels of −10 dB, 0.5 and 0.5 bits/s/Hz respectively, signifying good diversity performance of the proposed MIMO antenna.

A four port circularly polarized printed multiple‐input multiple‐output antenna with enhanced isolation

SummaryIn this article, a four‐port circularly polarized printed multiple‐input multiple‐output (MIMO) antenna is designed to cover Wi‐Fi/WLAN (5 GHz), Wi‐MAX (3.4–3.6), and C band applications, which consists of four trapezoidal shaped patches with microstrip feed. To achieve high isolation between the ports, the antenna elements are located orthogonally to each other. The antenna elements are separated by placing diagonal lines to further enhance the port isolation. Circular polarization is achieved by modifying the ground plane and trimming the edges of the trapezoidal patch. The proposed MIMO antenna works between 3.2 and 6.2 GHz and has a 63.83% impedance bandwidth (IBW) for S11 ≤ −10 dB. It also offers a good diversity performance with envelope correlation coefficient (ECC) &lt; 0.04 and diversity gain of ≈10 dB. The antenna is fabricated on a low‐cost FR4 material with 1.6 mm thickness and has dimensions of 50 mm × 50 mm. This article also clarifies some of the prior literature's misconceptions about MIMO antenna metrics. The measured results show that the proposed MIMO antenna is circularly polarized, has a similar IBW, and axial ratio bandwidth (ARBW) to the simulated results, and has &gt;25‐dB isolation.

An ultra‐wideband multiple‐input multiple‐output antenna with dual band‐notched characteristics

In this paper, an ultra-wideband multiple-input multiple-output antenna with dual band-notched characteristics is proposed. The radiating element is an octagonal structure using a tapered microstrip line to feed. A multimode resonator is introduced on one side of the microstrip feed line to achieve dual band-notched characteristics, which eliminates the interference of wireless local area network band and X satellite communication frequency band. By using a diamond-shaped defect ground structure and extending a parasitic branch at the centre axis of the ground, the mutual coupling of the antenna is reduced to −20 dB. The proposed antenna has a compact size of 30 × 35 × 0.8 mm3. The measured results are in good agreement with the simulation results. The proposed antenna covers 3.1–10.6 GHz with dual notched-band characteristics and the mutual coupling below −20 dB. The antenna has a good diversity performance as the envelope correlation coefficient <0.03. The antenna is suitable for ultra-wideband communications.

Isolation enhanced compact dual-band quad-element MIMO antenna with simple parasitic decoupling elements

In this work, a simple parasitic decoupling structure integrated compact dual-band quad-element Multiple-Input Multiple-Output (MIMO) configuration with improved isolation is proposed for 3.5 and 5.8 GHz bands of Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) applications. The lower and higher frequency bands accomplish an impedance bandwidth of 400 MHz (3.35 – 3.75 GHz) and 450 MHz (5.6 – 6.05 GHz), respectively. A slot integrated curve-shaped compact (11 × 20 mm2) dual-band monopole antenna is explored to implement the proposed compact MIMO configuration. A parasitic decoupling structure comprising T and inverted L-shaped thin metal strips is introduced between the orthogonally placed antenna elements. It exhibits dual stopband characteristics to enhance the isolation significantly at the targeted frequency bands despite the compact footprint (34 × 34 mm2) of the MIMO geometry.The optimized decoupling structure improves the isolation between the elements by 31.5 and 32 dB in the lower and higher bands than the MIMO geometry without decoupling elements. The antenna provides good radiation characteristics with peak gains of 4.18 and 3.62 dBi within the bands. The computed diversity metrics, such as envelope correlation coefficient (< 0.01), diversity gain (> 9.93 dB), mean effective gain ratio (-0.13 to 0.16 dB), channel capacity loss (< 0.4 b/s/Hz), and total active reflection coefficient (< -10 dB), ensures good diversity performance. The fair agreement between the simulated results using HFSS EM solver and the measured results on the fabricated prototype validated the proposed MIMO configuration.

A Planar Printed Four-Element Pattern Diversity MIMO Antenna Based on Novel Quasi-Yagi Elements

In this paper, a new planar printed quasi-Yagi antenna with compact size and wide bandwidth is presented for a multiple-input-multiple-output (MIMO) antenna system. Antenna element consists of a rectangular driven monopole, a strip director, and a coplanar ground shorted reflector. A planar rectangular monopole is used for the first time as a driven element instead of a dipole to avoid the implementation complexity of BALUN as it can be fed directly by an unbalanced coaxial feed. It has been shown that the antenna element has an impedance bandwidth (|S 11| < −10 dB) of 60.5% ranging from 1.59 to 2.97 GHz. Based on this element, a four-element pattern diversity MIMO antenna is proposed. By utilizing the ground of one element as a reflector for the successive element, a compact size of 109 mm × 109 mm (0.54λ 0 × 0.54λ 0 at 1.5 GHz) has been obtained. Measured bandwidth of 65.9% (1.5–2.97 GHz) with minimum isolation of 13 dB has been achieved. The measured directional patterns and an average gain of 4 dBi, remain stable in the operating band with cross-polarization levels less than −25 dB. The envelope correlation coefficient and channel capacity loss show good diversity performance.

A single-layer compact four-element quasi-Yagi MIMO antenna design for super-wideband response

In this article, a new configuration of a multiple-input-multiple-output (MIMO) antenna system for super-wideband response is presented. The proposed antenna consists of four microstrip line-fed compact 3-elements quasi-Yagi antennas placed perpendicularly to each other. Each element has a bow-tie-driven monopole element over a finite ground plane backed by a flared truncated ground reflector and a diamond-shaped director. The end-fire radiation pattern over the wider bandwidth has been achieved using a bow-tie monopole-driven element. The measured impedance bandwidth (for |S11| ≤ −10 dB) is from 1.37 to 16 GHz (168.5% at 8.68 GHz mid-frequency), and port isolation is better than 16 dB with a common ground plane. The measured gain and efficiency variations are between 3.5 and 5.4 dBi and 56–90%, respectively. These characteristics are in good agreement with theoretical results. The calculated envelope correlation coefficient and capacity loss are less than 0.01 and 0.25 bit/s/Hz, respectively, over the entire operating band. The overall size of the proposed MIMO antenna is 110 × 110 × 1.6 mm3. The novelty of the proposed antenna system is the four directive beams and good diversity performance over super-wide bandwidth with a simple single-layer compact design, which makes it a promising candidate for large-capacity and high-speed communication systems.

Four-element pentaband MIMO antenna for multiple wireless application including dual-band circular polarization characteristics

AbstractIn this article, a meander line-shaped pentaband (2.18–2.24, 2.38–2.46, 2.65–2.70, 3.10–3.32, 3.38–3.46 GHz) four-element multiple-input–multiple-output antenna is presented. The proposed antenna is also circularly polarized in two bands (at 2.2 and 2.4 GHz) with dual-polarization like right-handed at port 1 or 3 and left-handed at port 2 or 4, which is widely used for mobile satellite services (MSS) and Internet of Things applications. This antenna is designed and fabricated with compact size 50 × 70 × 1.6 mm3 on the FR-4 substrate with good diversity performance in pentaband. Simulated results of antenna-like return loss, isolation, and parameters-related diversity have also been tested experimentally in a controlled environment, which is within the permissible limit. The designed antenna will be appropriate for MSS, industrial scientific and medical (ISM), broadband radio services and educational broadband services, WiMAX radio location services, and amateur radio services. Meanwhile, specific absorption rate of the designed antenna has been examined in an empirical environment for the Fresnel radiating near-field applications.

Reconfigurable orthogonal quad-port MIMO antenna for DSRC, WLAN, RADAR and Ku-band applications

A novel and compact reconfigurable quad-port orthogonal Multi-Input-Multi-Output (MIMO) antenna is proposed for Dedicated Short Range Communication (DSRC), WLAN, RADAR and Ku-band applications. The proposed MIMO antenna is fabricated on FR-4 substrate of dimensions 40 × 40 × 0.8 mm3. Each element of MIMO antenna has attained different Ku-band frequencies and lower frequency operating band 5.5–9.2 GHz suitable for DSRC, WLAN and RADAR applications is obtained by M-3 element of proposed MIMO antenna for diode ON condition in ground plane. Individual MIMO element is investigated with respect to S-parameters, isolation, current distribution, radiation pattern, gain, radiation efficiency, Total Active Reflection Coefficient (TARC) and diversity performance parameters like Envelope Correlation Coefficient (ECC), Diversity Gain (DG) and Mean Effective Gain (MEG). Overall gain of MIMO antenna ranges between 3.36 and 7.57 dB in operating bands and radiation efficiency ranges between 70.4 and 89.7%. Time domain characteristics are analyzed using group delay with respect to all ports and group delay is less than 1.5 ns. ECC values are below 0.05, DG is very close to 10 and MEGi < −3 dB. The proposed quad-port MIMO antenna exhibits good diversity performance and is validated by comparing computer generated and experimental results.

Miniaturize four‐port UWB‐MIMO antenna with tri‐notched band characteristics

AbstractIn this article, a compact and high performance 4‐port ultra‐wideband multiple‐input multiple‐output antenna is presented. The proposed antenna is designed by using a novel technology which includes integration of four orthogonal octad‐shaped radiators, four D‐shaped ground planes, multi‐stub techniques and slot techniques. The overall size of the design is effectively miniaturized and the ultra‐wideband characteristics are achieved through feed line tapering and by inserting slot in the D‐shape ground structure. Moreover, tri‐band notch characteristics are achieved in the proposed design by embedding L‐shaped stubs in the octad radiating elements. This results in impedance bandwidth of 2.6‐12.2GHz with notched characteristics at bands ranging from 3‐3.7GHz, 5‐6GHz and 7.9‐8.3GHz. In addition, the antenna shows high isolation and good diversity performance in terms of Envelop Correlation coefficient, Diversity gain and Total active reflection coefficient. A good trade‐off of performance has achieved from the proposed design makes it best candidate for wireless communication applications.

Wideband Decoupling of Integrated Slot Antenna Pairs for 5G Smartphones

This communication proposes a wideband decoupling technique to suppress the strong coupling between two extremely closely spaced open-slot antennas and implements a wideband integrated slot antenna pair for fifth-generation (5G) metal-rimmed smartphones. By simply inserting a connecting line between two closely spaced open-slot antennas, a top slot structure can be constituted with odd- and even-mode resonances in the lower and higher bands, respectively, to cancel the original strong mutual coupling. In addition to the decoupling effect, the top slot can also expand the effective radiation aperture of the antenna pair for the bandwidth improvement. The proposed slot antenna pair, with a compact footprint of 28 ×7 ×1.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , shows good impedance matching, isolated and diversity performance across 3.3-5.0 GHz. Then, an 8 ×8 multiple-input multiple-output (MIMO) system, constituted by four sets of slot antenna pairs, is simulated, fabricated, and measured. Both the simulated and experimental results show that the 8 ×8 MIMO system can offer isolations of better than 10.8 dB and envelope correlation coefficients (ECCs) of less than 0.14 between all eight ports across 3.3-5.0 GHz. Also, a total efficiency of 55.0%-83.1% and 52.5%-83.1% is achieved for Ant1 and Ant2, respectively. Featuring wide bandwidth, compact size, high integration level, and metal rim compatibility, we forecast the proposed solution has great potential for future 5G smartphones.