A CPW‐fed UWB MIMO antenna with integrated GSM band and dual band notches

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 reduced size dual port MIMO DRA with high isolation for 4G applications

A dual‐port reduced size multiple input multiple output (MIMO) Dielectric Resonator Antenna (DRA) has been studied and proposed. The MIMO antenna consists of a Rectangular Dielectric Resonator antenna, which is fed by two symmetrical feed lines for orthogonal mode excitation. The proposed antenna is suitable for operation over various long term evolution (LTE) bands. A measured bandwidth of 264 MHz for |S₁₁| S‐parameters. Based on these results, it can be concluded that the proposed antenna can be a suitable candidate for MIMO applications. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:495–501, 2015.     

Dielectric resonator based two‐port dual band antenna for MIMO applications

This article investigates a dual band multiple input multiple output (MIMO) cylindrical dielectric resonator antenna (cDRA) for WLAN and WiMAX applications. It consists of two symmetrical orthogonally placed radiators. Each radiator is excited through a narrow rectangular aperture with the help of a microstrip line. For higher mode excitation, the proposed structure uses dual segment DRA which apparently looks like stacked geometry. The aperture fed dielectric resonator works as a feed for upper cDRA to generate higher order mode. The presented radiator covers the band between 3.3‐3.8 GHz and 5‐5.7 GHz. The measured isolation is better than 20 dB in the desired band. The average gain and radiation efficiency achieved for the proposed antenna is 6.0 dBi and 85%, respectively at the operating frequency band. In the proposed geometry, broadside radiation patterns are achieved by exciting HEM_11δ and HEM_12δ modes in a stacked geometry. Different MIMO performance parameters (ECC, DG, MEG, and CCL) are also estimated and analyzed. The prototype of proposed antenna is fabricated and tested. The measured outcomes are in good accord with the simulated one.     

High isolation two‐port compact MIMO fractal antenna with Wi‐Max and X‐band suppression characteristics

This article features about an ultra‐wideband (UWB)‐multiple‐input multiple‐output (MIMO) antenna that exhibits the potentials of good port isolation and dual‐band suppression. The proposed antenna model consists of a unique fractal‐shaped radiating patch, a common ground interface leading to the incorporation of an intuitive approach; parasitic inverted neutralization stubs, which is located at the central co‐ordinate axis system, protruded vertically, where its extension is twisted with a motive of enhancing the port isolation. In addition to that, contiguous notches are implemented to achieve band‐notching at WiMAX (3.35‐4.45 GHz) and X‐band (9‐10 GHz). The total electrical area of UWB MIMO antenna is 0.179(λ₀)² at 2.25 GHz. To rationalize the counterparts of MIMO and band‐notching, diversity performance is studied through the electromagnetic (EM) solver and the corresponding circuit analysis is pursued through a electronic design automation (EDA) solver. The prototype has been fabricated, measured, and agreed well with the simulated results. The feasibility of proposed antenna model is considered to be quite optimum, with due consideration of its outcomes from applications point‐of‐view.     

Reduced mutual coupling of compact MIMO antenna designed for WLAN and WiMAX applications

This communication describes a simple compact wide band multiple input multiple output (MIMO) antenna for Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The proposed antenna is integrated with an electromagnetic band gap (EBG) structure which is used to reduce the mutual coupling between the ports. The structure is excited by a line feed mechanism and investigated experimentally. The antenna covers the frequency range from 2.01 to 3.92 GHz with the corresponding fractional bandwidth of 64.42%. It fulfills the bandwidth requirements of WLAN (2.35‐2.5 GHz) and WiMAX (3.2‐3.85 GHz) bands where minimum port isolation is obtained around 29 dB throughout the entire application band. The proposed MIMO antenna has very low envelope correlation co‐efficient (ECC < 0.01) and high diversity gain (DG > 9.8). It also has very low channel capacity loss (CCL) which is found to be less than 0.2 Bit/s/Hz. The simulation results are compared with the measurement outcomes and found a good agreement between them.     

Low profile four‐port super‐wideband multiple‐input‐multiple‐output antenna with triple band rejection characteristics

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.     

A compact six port antenna for better spectrum utilization efficiency in cognitive radio applications

In this article, a novel six port antenna for better spectrum utilization efficiency in cognitive radio (CR) applications is presented. In this six port antenna system, an ultra‐wideband (UWB) sensing antenna and five wideband/narrowband (NB) antennas are integrated on the same substrate in a compact area of 1134 mm² . Antenna associated with port 1, which is meant for sensing, has ?10 dB reflection coefficient bandwidth of 3 to 11 GHz and the antennas associated with ports 2, 3, 4, 5, and 6 have ?10 dB reflection coefficient bandwidths of 3.6 to 5.8 GHz (single band), 2.9 to 3.6 GHz and 5.4 to 7.98 GHz (dual band), 7.95 to 8.38 GHz and 9 to 9.85 GHz (dual band), 8.38 to 9 GHz (single band) and 9.7 to 10.7 GHz (single band), respectively. Minimum isolation of 20 dB is attained between UWB sensing antenna and any narrowband/wideband antenna except between the antennas associated with ports 1 and 2 where minimum isolation of 12 dB is achieved over the operating bandwidth of UWB sensing antenna. Moreover, among all wideband/narrowband antennas, isolation of less than 15 dB is achieved. More importantly, the narrowband and wideband antennas meant for communication cover all frequency bands in UWB and a good match between the simulated and measured results is noticed.     

A dual‐feed MIMO antenna pair with one shared radiator and two isolated ports for fifth generation mobile communication band

In this article, a pair of unsymmetrical dual‐feed antennas with one shared radiator and two isolated ports is proposed for multiple‐input‐multiple‐output (MIMO) systems. The proposed antenna pair achieves high isolation between the two ports by properly adjusting the distance between the two feeding ports and the position and length of shorting strips on the radiator. The antenna has simple structure and covers the 3.3‐3.7 GHz band, which could meet the demand of future 5G applications. The measured results show that antenna has good impedance matching (better than 10 dB return loss) and high port isolation (better than 20 dB isolation) from 3.35 to 3.65 GHz. The total efficiencies are above 55% and the envelope correlation coefficient is <0.1, which is sufficient for MIMO applications.     

Circularly polarized V‐shaped dielectric resonator antenna

In this article, a probe fed V‐shaped dielectric resonator antenna (DRA) loaded with circular patches, is proposed for X band applications. A prototype was fabricated to validate the results. Circular polarization is achieved by the geometry of DRA integrated with the circular patches on its surface. These circular patches behave as a monopole antenna. To achieve circular polarization two orthogonal fields have been excited in the DRA, which are in time phase quadrature. Due to the symmetry of design, it shows dual polarization, both Left Hand Circular Polarization (LHCP) and Right Hand Circular Polarization (RHCP), in two orthogonal directions. The fabricated prototype exhibits wide impedance bandwidth of 7.85‐10.1 GHz (25%) and circular polarization (CP) Bandwidth (BW) of 8.35‐8.7 GHz (4%). Maximum measured gain of 4.8 dBi has been obtained in comparison with the simulated gain of 5.6 dBi. Applications of the proposed antenna include satellite communication, telemetry tracking and control, Synthetic aperture radar (SAR), weather radar, and military radar in X band. Directional CP performance is useful in designing a smart antenna and multiple input multiple output (MIMO) antenna.     

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 planar frequency reconfigurable multiple‐input‐multiple‐output antenna with pattern and polarization diversity characteristics for WiFi and WiMAX standards

A compact planar frequency reconfigurable dual‐band multiple‐input‐multiple‐output (MIMO) antenna with high isolation and pattern/polarization diversity characteristics is presented in this article for WiFi and WiMAX standards. The MIMO configuration incorporates two symmetrically placed identical antenna elements and covers overall size of 24 mm × 24 mm × 0.762 mm. Reconfiguration of each antenna element is achieved by using a PIN diode which allows antennas to switch from state‐1 (2.3‐2.4 GHz and 4.6‐5.5 GHz) to state‐2 (3.3‐3.5 GHz and 4.6‐5.5 GHz). In state‐1, the configuration offers isolation ≥18 dB and 20 dB in lower band (LB) and upper band (UB) respectively; whereas, in state‐2, isolation ≥21 dB and 20 dB in LB and UB respectively is achieved. The same decoupling circuit provides high isolation in dual‐band of two states, which makes overall size of the proposed design further compact. The antennas are characterized in terms of envelope correlation coefficient, radiation pattern, gain, and efficiency. From measured and simulated results, it is verified that the proposed frequency reconfigurable dual‐band multi‐standard MIMO antenna design shows desirable performance in both operating bands of each state and compact size of the design makes it suitable for small form factor devices used in future wireless communication systems.     

Dual‐band circularly polarized MIMO DRA for sub‐6 GHz applications

In this article, a dual‐band circularly polarized multiple‐input‐multiple‐output (MIMO) dielectric resonator antenna (DRA) is proposed for 3.5 and 5.5 GHz bands, both being located under 6 GHz. Known as sub‐6 (or as mid‐band), they provide good coverage and capacity in the newly targeted fifth‐generation (5G) systems. The proposed structure consists of two ring DRAs (RDRAs) etched on a 0.8 mm thick RT Duroid substrate. Measured impedance bandwidths in broadside direction are 3.1‐3.75 GHz (19%) and 5.3‐5.6 GHz (9.4%) and circular polarization (CP) bandwidths are 3.425‐3.6 GHz (5%) and 5.45‐5.55 GHz (2%), respectively. CP is achieved by exciting HE modes using two probes placed orthogonaly to each other, that is, at an azimuthal angular distance of 90^° . Varying the lengths of the probe allows achieving the necessary time‐phase quadrature between modes. Comparison between recent multiband circularly polarized MIMO DRAs and proposed prototype has revealed that CP bandwidth in both bands is one of the highlighting advantages of the present configuration.     

Complementary meander‐line‐inspired dielectric resonator multiple‐input‐multiple‐output antenna for dual‐band applications

The communication presents a simple dielectric resonator (DR) multiple‐input‐multiple‐output (MIMO) dual‐band antenna. It utilizes two “I”‐shaped DR elements to construct an “I”‐shaped DR array antenna (IDRAA) for MIMO applications. The ground plane of the antenna is defected by two spiral complementary meander lines and two circular ground slots. In the configuration, two “I”‐shaped DR elements are placed with a separation of 0.098λ. The antenna covers dual‐band frequency spectra from 3.46 to 5.37 GHz (43.26%) and from 5.89 to 6.49 GHz (9.7%). It ensures the C‐band downlink (3.7‐4.2 GHz), uplink (5.925‐6.425 GHz), and WiMAX (5.15‐5.35 GHz) frequency bands. Each DR element is excited with a 50‐Ω microstrip line feed with aperture‐coupling mechanism. The antenna offers very high port isolation of around 18.5 and 20 dB in the lower band and upper band, respectively. The proposed structure is suitable to operate in the MIMO system because of its very nominal envelope correlation coefficient (<0.015) and high diversity gain (>9.8). The MIMO antenna provides very good mean effective gain value (±0.35 dB) and low channel capacity loss (<0.35 bit/s/Hz) throughout the entire operating bands. Simulated and measured results are in good agreement and they approve the suitability of the proposed IDRAA for C‐band uplink and downlink applications and WiMAX band applications.     

Dual‐functional QM SIW cavity integrating two‐element MIMO antenna and second‐order bandpass filter

A quarter‐mode (QM) substrate‐integrated‐waveguide (SIW) cavity is designed as a dual‐functional component. By etching three slots, four sub‐cavities are formed and then two of them with the same size are individually fed by a coaxial port. Three resonating frequencies are excited in the single QM SIW cavity. One of them can radiate cavity energy input by these ports into free space, implying a two‐element multiple‐input‐multiple‐output (MIMO) antenna, whereas the other two can transmit energy from one port to the other port, indicating a second‐order bandpass filter. Moreover, antenna isolation and filter bandwidth can be adjusted to a certain degree. A prototype with the overall size of 0.40λ₀ × 0.40λ₀ × 0.02λ₀ has been fabricated. The integrated bandpass filter demonstrates the measured center frequency of 3.8 GHz and operating bandwidth of 32 MHz while the integrated MIMO antenna exhibits the frequency of 3.4 GHz, bandwidth of 67 MHz, port isolation of 18.0 dB, radiation gain of 4.0 dBi, and envelope correlation coefficient of 0.25.     

Ultra‐compact 4‐port DR antenna for multi‐input multi‐output standards

Here, an ultra‐compact Multi‐Input‐Multi‐Output (MIMO) antenna system is presented for Wireless Local Area Network (WLAN) applications. The proposed antenna compactness approach is based on using Cylindrical‐Dielectric‐Resonator‐Antenna (CDRA) symmetry with the help of image theory to achieve the best size reduction of the resonators and maintain the resonance frequency of the original CDRA. The electric/magnetic walls approach is utilized to miniaturize the size by exploring the symmetry and antisymmetry of the resonant mode. First, a CDRA for MIMO system is designed and tested in terms of return loss and radiation efficiency. Then, two configurations of MIMO‐Antennas (two and four ports) are examined by using the same substrate size. The 2‐port‐MIMO antenna is built from two half‐CDRs (HCDRs) facing each other. Similarly, four‐quarter‐CDRs (QCDRs) are created to form a 4‐port MIMO antenna system. As a result, a 75% size reduction is achieved (size of 30 × 30 × 7.62 mm³). The measured impedance bandwidth for the 4‐port MIMO antenna is 5.4% (5.4‐5.7 GHz), with more than 15 dB isolation levels. Proper levels of Envelope Correlation Coefficients (ECCs) are also achieved (1 × 10^?2‐4 × 10^?2), with a channel capacity loss (CCL) of 0.04 bits/S/Hz. The proposed MIMO antennas are suitable for compact wireless communication systems.     

CSRR‐loaded T‐shaped MIMO antenna for 5G cellular networks and vehicular communications

This article proposes a multiple input multiple output (MIMO) antenna for 5G‐based vehicular communication applications. The designed MIMO antenna consist of two element iterated T‐shape antenna with defected ground structure (DGS) and split ring resonator. The antenna providing reflection coefficient S₁₁ s₁₁ ≤10 dB and bandwidth of 6.3 and 3.96 GHz over the frequency range of 26.83 to 33.13 GHz and 34.17 to 38.13 GHz, respectively. For the suitable future vehicular millimetric wave communications, this antenna achieved resonant frequencies at 28, 33, and 37 GHz. The designed antenna has achieved peak gain of 7.11 dB in operating band. It is fabricated on 12 x 25.4 x 0.8 mm³ Rogers RT duroid 5880 substrate with dielectric constant (ε_r) of 2.2. The antenna is placed on vehicle in virtual environmental using ANSYS SAVANT tool and the simulated results are showing good matching with the measured results of proposed MIMO antenna.     

A‐shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

In this article, a new A‐shaped dielectric resonator antenna (DRA) excited by a conformal strip is proposed for wideband applications. The wide bandwidth is achieved by combining two adjacent modes that is, TM₁₀₁ and TM₁₀₃. The experimental results demonstrate that the proposed DRA offers an impedance bandwidth (for S11?10 dB) of 59.7% (3.24‐6.0 GHz), covering IEEE 802.11 and U‐NII bands. The antenna provides a fairly stable radiation pattern with the gain ranging from 5.29 to 7 dBi across the operating bandwidth. A dual‐element multiple‐input multiple‐output (MIMO) system is also realized using the proposed wideband DRA. The impedance bandwidth of the dual‐element MIMO antenna is 59.2% and 60.9% for Port1 and Port2, respectively and the isolation between the ports is better than 20 dB across the bandwidth. For Port1, the gain of the MIMO antenna ranging from 6.03 to 7.45 dBi is obtained across the bandwidth. Furthermore, the diversity performance of the MIMO antenna is found to be good with envelope correlation coefficient below 0.003 over the operating band. The proposed antenna could be the potential candidate for worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN) and lower European UWB frequency band (3.4‐5.0 GHz) applications.     

Design of a compact triple band antenna with independent frequency tuning for MIMO applications

In this article, a planar, low profile microstrip line‐fed triple band multiple input multiple output (MIMO) antenna is presented for WiMax (2.5/3.5/5.5 GHz)/WLAN (2.4/3.6/5.8 GHz) applications simultaneously. The single element of the MIMO antenna consists of (i) a rectangular split ring resonator (SRR), (ii) a stepped impedance resonator (SIR) inside the SRR and (iii) a slot on the SIR. Each of the resonators generates its own individual band and each band is independently tunable. The antenna exhibits three operating bands at 2.35‐2.85 GHz, 3.25‐3.90 GHz and 5.45‐5.65 GHz. Four antenna elements are used to design the proposed MIMO antenna. The simulated results are observed and reported in terms of S‐parameters, gain, radiation patterns, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL) and total active reflection coefficient. ECC and CCL are within the acceptable range defined for 4G and 5G application standards. To validate the simulation results a prototype structure is fabricated and the measured results are compared with those obtained from the simulation.     

Wide‐bandwidth multifrequency circularly polarized monopole antenna for wireless communication applications

In this article, wideband circularly polarized monopole antennas with multiresonating frequencies are presented for Bluetooth, WLAN, WiMAX, and X‐band applications. The designed antennas have dimensions of 50 × 35 × 1.6 mm³. Two different substrates (FR4‐epoxy and PTFE) are used for fabricating the antennas. The antennas consist of corner truncated I‐shaped and C‐shaped strips excited by a 50 Ω microstrip feed line. The parametric analyses are performed with the help of Ansoft HFSS V.11 EM simulator. Both antennas have been fabricated and measured. The measured percentage bandwidth of the antenna made by FR4 substrate is 31.32% (centered at 1.66 GHz), and 64.85% (centered at 5.69 GHz). The percentage bandwidth of antenna made by PTFE substrate is 20.57% (centered 2.43 GHz) and 68.74% (centered at 7.39 GHz). In addition to that, there exists 3 dB AR bandwidth for LHCP of about 1050 MHz for 5.2 GHz WLAN‐band. The reflection coefficient, radiation patterns, and the gains of both the antennas are studied in detail. It is found that the measured and simulated results are in good agreement.     

Dual‐polarized textile‐based two/four element MIMO antenna with improved isolation for dual wideband application

This article presents the designs of dual‐polarized dual wideband textile‐based two and four elements multiple‐input multiple‐output (MIMO) antennas for WLAN (IEEE 802.11a/b/g/c/n) and WiMAX (IEEE 802.16d) applications. These MIMO antennas cover the frequency spectra from 1.5 to 3.8 GHz (87% bandwidth) and 4.1 to 6.1 GHz (40% bandwidth). The characterization of the textile jeans substrate is determined experimentally using a vector network analyzer and dielectric assessment kit. These antennas provide near about 70% radiation efficiency with around 4 dBi peak gain in desired frequency ranges. The diversity performance is improved noticeably by printing meandered line structures on both planes. The proposed MIMO structure has a very low envelop correlation coefficient (ECC) <0.1 and high diversity gain (DG) >9.9. The Medium effective gain (MEG) also lies within a satisfactory value of ±3 dB. The two elements MIMO Antennas provide linear polarization at all desired frequency band while the four‐element antenna provides circular polarization at 2.4 GHz and linear polarization at 5.2 and 5.8 GHz application bands. The antenna also depicts good performance in wearable condition with safe specific absorption rate < 1.6 W/kg in all desired frequencies.