A dual‐band antenna design for MIMO LTE applications with reduced ground effects

A dual‐band planar long term evolution (LTE) antenna design is initially proposed. The size of this proposed antenna is 40 mm × 15 mm × 0.8 mm, and its structure is meticulously designed to achieve reduce ground effects, so that the ground plane size can be altered without affecting the antenna's performance. The 6‐dB impedance bandwidths of both lower and upper operating bands of proposed antenna are 13.1% (695–790 MHz) and 37.6% (2200–3120 MHz), respectively. Minimum radiation efficiencies of up to 56% are also exhibited within the three LTE bands (LTE 700/2300/2600 MHz). This proposed antenna is later used as a two‐antenna multiple input multiple output (MIMO) system for laptop computer application, and because of its reduced ground effects, good envelope correlation coefficient (ECC) of less than 0.14 and 0.0022 are measured across the lower and upper operating bands, respectively. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:80–87, 2016.     

Design of a dual‐band MIMO dielectric resonator antenna with high port isolation for WiMAX and WLAN applications

A novel dual‐band MIMO dielectric resonator antenna with high port isolation for WiMAX and WLAN applications is designed and investigated. The proposed antenna operates at 3.5 and 5.25 GHz bands. High port isolation is achieved using hybrid feeding mechanism that excites two orthogonal modes at each frequency bands. The measured impedance bandwidth of the proposed antenna covers the entire WiMAX (3.4–3.7) GHz and WLAN (5.15–5.35) GHz bands. The scalable behavior along with the frequency ratio of the antenna has also been investigated in this work. The measured isolation between antenna ports is ?52 dB at the lower band and ?46 dB at the upper band, respectively. Envelope correlation coefficient, diversity gain and mean effective gain have also been investigated. Moreover, measured results are in good agreement with the simulated ones.     

A metamaterial hepta‐band antenna for wireless applications with specific absorption rate reduction

Present article embodies the design and analysis of slotted circular shape metamaterial loaded multiband antenna for wireless applications with declination of SAR. The electrical dimension is 0.260 λ × 0.253 λ × 0.0059 λ (35 × 34 × 0.8 mm³) of proposed design, at lower frequency of 2.23 GHz. The antenna consists of circular shape rectangular slot as the radiation element loaded with metamaterial split ring resonator (SRR) and two parallel rectangular stubs, etched rectangular single complementary split‐ring resonator (CSRR) and reclined T‐shaped slot as ground plane. Antenna achieves hepta bands for wireless standards WLAN (2.4/5.0/5.8 GHz), WiMAX (3.5 GHz), radio frequency identification (RFID) services (3.0 GHz), Upper X band (11.8 GHz—for space communication) and Lower K_U band (13.1 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The SRR is responsible for creating an additional resonating mode for wireless application as well as provide the declination in SAR about 13.3%. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

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.     

Compact C‐shaped MIMO diversity antenna for quad band applications with hexagonal stub for isolation improvement

A compact MIMO antenna was proposed in this article. The designed antenna is compact in size with dimensions of 20 × 34 × 1.6 mm. In this proposed antenna model the patch consisting of two counter facing C‐shaped elements facing each other in which a hexagonal ring attached to a strip line which is placed in between the two C‐shaped patch acts as the stub. The novelty of the antenna elements lies isolation improvement by using the ground stub with the use of circular ring resonator. The proposed antenna operates in four bands in which 2.66 to 3.60 GHz (Wi‐Max, Wi‐Fi), 4.52 to 5.78 GHz (WLAN), 6.59 to 7.40 GHz (satellite communication), and 9.55 to 10.91 GHz and having bandwidth of 0.94, 1.26, 0.81, and 1.36 GHz at four bands. The envelope correlation coefficient is ECC ≤ 0.3 and diversity gain > 9.8 dB for the operating bands of antenna proposed. This antenna can work in the bands of Wi‐Max, Wi‐Fi, WLAN, satellite communication in X‐band and for radio location, and astronomy applications.     

A thin‐layer dielectric and metamaterial unit‐cell stack loaded miniaturized SRR‐based antenna for triple narrow band 4G‐LTE applications

This article presents the design of a miniaturized dual‐band antenna for long‐term evolution (LTE) application is presented. In the basic antenna design, split ring resonator was loaded in the radiating plane of the patch and frequency of resonance was further modified with the help of E‐shaped stub. The antenna has been fabricated using FR‐4 substrate and the measured dual bands at 2.11 and 2.665 GHz are found in a close match with the simulated data. By placing a thin dielectric resonator of permittivity ε _r = 10.2 and thickness of 1.27 mm, two closely spaced narrow bands are obtained at 2.217 and 2.28 GHz. A novel metamaterial unit‐cell having near‐zero refractive index is designed and mounted above the dielectric resonator. This stack configuration generates triple narrow frequency band in the LTE 2 GHz spectrum range. The overall size of the proposed antenna is 20 × 25 mm².     

Design and fabrication of a new high gain multilayer negative refractive index metamaterial antenna for X‐band applications

This article presents the design of a planar high gain and wideband antenna using a negative refractive index multilayer superstrate in the X‐band. This meta‐antenna is composed of a four‐layer superstrate placed on a conventional patch antenna. The structure resonates at a frequency of 9.4 GHz. Each layer of the metamaterial superstrate consists of a 7 × 7 array of electric‐field‐coupled resonators, with a negative refractive index of 8.66 to 11.83 GHz. The number of layers and the separation of superstrate layers are simulated and optimized. This metamaterial lens has significantly increased the gain of the patch antenna to 17.1 dBi. Measurements and simulation results proved about 10 dB improvement of the gain.     

A compact wide band textile MIMO antenna with very low mutual coupling for wearable applications

This communication presents a compact wide band wearable MIMO antenna with very low mutual coupling (VLMC). The proposed antenna is composed of Jeans material. Two “I” shaped stubs are connected in series and are employed on the ground plane between the two patches separated by 0.048 λ to increase isolation characteristics of the antenna‐port. The antenna covers frequency spectrum from 1.83 GHz to 8 GHz (about 125.5%) where the minimum port isolation of about 22 dB at 2.4 GHz and maximum of about 53 dB at 5.92 GHz are obtained. The envelope correlation coefficient (ECC) of the MIMO antenna is obtained to be less than 0.01 with a higher diversity gain (DG > 9.6) throughout the whole operating band. The proposed MIMO antenna is cost effective and works over a wide frequency band of WLAN (2.4‐2.484 GHz/5.15‐5.35 GHz/5.72‐5.825 GHz), WiMAX (3.2‐3.85 GHz) and C‐band downlink‐uplink (3.7‐4.2 GHz/5.925‐6.425 GHz) applications. Simulation results are in well agreement with the measurement results.     

A low‐profile dual port UWB‐MIMO/diversity antenna with band rejection ability

A band notched ultra‐wideband (UWB) antenna is presented in this article as a good prospect for multiple‐input multiple‐output (MIMO)/diversity application. The proposed MIMO antenna is constituted of two modified rectangle‐shaped patch antenna elements. A stepped stub is extended from the modified ground plane as a decoupling element between the radiators to realize a good isolation level between them. A band rejection response is obtained by connecting an open resonant stub to each of the radiators. The simulated prototype is fabricated and tested for verification. Results reveal that the proposed prototype provides a 10 dB return loss bandwidth from 3.08 to 10.98 GHz with band notch characteristics from 4.98 to 5.96 GHz, and a good port isolation level (S₂₁ ≤ 20). Diversity performances are ensured in terms of total active reflection coefficient, envelope correlation coefficient (<0.013 except notch band), diversity gain (≈9.51 dB), mean effective gain ratio (≈1), and channel capacity loss (≤0.35 bps/HZ except notch band). It evidences that the presented band notched UWB antenna can be a good prospective for MIMO/diversity applications.     

Compact multiband planar monopole antenna for Bluetooth,LTE, and reconfigurable UWB applications including X‐band and Ku‐band wireless communications

In this article, a small‐printed Bluetooth/LTE/UWB/X‐band/Ku‐band monopole antenna with high rejection triple band‐notch is presented. Notched bands include WiMAX (IEEE802.16 3.30‐3.80 GHz), WLAN IEEE802.11a/h/j/n (5.15‐5.35 GHz, 5.25‐5.35 GHz, 5.47‐5.725 GHz, and 5.725‐5.825 GHz), and downlink satellite system (7.1‐7.9 GHz). By including inverted T‐shaped stub and etching two C‐shaped slots on the radiating patch, triple band‐notch function is obtained with measured high band rejection (VSWR = 14.59 at 3.69 GHz, VSWR = 39.40 at 5.42 GHz, and VSWR = 6.43 at 7.57 GHz) and covers a UWB useable fractional bandwidth of 157.75% (2.285‐19.35 GHz = 17.065 GHz). Reconfigurable characteristics are obtained using PIN diodes, which control the individual notched bands. Proposed antenna is printed on Rogers RT/duroid5880 substrate with compact dimensions of 20 × 22 mm². Proposed antenna finds its applications for Bluetooth, LTE, UWB, other multiple wireless applications for close range radar (8‐12 GHz) in X‐band, and satellite communication in Ku‐Band with omnidirectional pattern in H‐plane.     

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.     

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.     

Carbon fiber‐based deca‐port multiple‐input‐multiple‐output antenna with pattern diversity and high inter‐element isolation

In this article, a deca‐port carbon fiber‐based multiple‐input‐multiple‐output (MIMO) antenna with pattern diversity is presented. The radiating elements of the proposed antenna consist of low cost, light weight, environmental friendly graphite material. The 10 radiating elements of the MIMO antenna are arranged in a group of two (termed as sub‐MIMO structure), in a cubical manner to cover all the propagating directions. Furthermore, the two carbon fiber‐based radiating elements of the sub‐MIMO structure are placed in an orthogonal arrangement to generate different radiation patterns. The antenna exhibits high inter‐element isolation and low envelope correlation coefficient due to orthogonal placement of the radiating elements. The antenna is fabricated and the measured results confirm that the proposed MIMO/diversity antenna may be useful for vehicle‐to‐network applications. The MIMO performance parameters such as diversity gain, total active reflection coefficient, mean effective gain, channel capacity loss are evaluated and found within suitable limits. The three‐dimensional pattern diversity helps to communicate in all directions.     

A tiny EBG‐based structure multiband MIMO antenna with high isolation for LTE/WLAN and C/X bands applications

This article proposes a compact multiple‐input multiple‐output (MIMO) antenna with the electromagnetic band gap (EBG) structures for mobile terminals. The proposed MIMO antenna is composed of two radiation patches in which diagonal and folded microstrip lines are utilized to control the frequency bands. The radiation patch, one EBG structure and a rectangular‐shaped ground plane are etched on both sides of the antenna. The EBG structures have been employed for reducing the mutual coupling between the antenna elements. As a result of the effect of these structures, the mutual coupling between the two elements is reduced by less than ?30 dB. The proposed antenna is implemented on an FR4 substrate with dimensions 20 × 10 × 1 mm³. According to measured results, frequency ranges of 2.2 to 3.6 GHz and 5.1 to 5.9 GHz with S₁₁ < ?10 dB and also 3.7 to 5 GHz and 8 to 12 GHz with S₂₂ < ?10 dB have been obtained. Moreover, measured S₁₂ and S₂₁ with values of less than ?30 dB for both Ports have been realized. Additionally, the envelope correlation and radiation efficiency of the purposed antenna are less than 0.09 and more than 82%, respectively.     

Multiband multiple‐input multiple‐output antenna with high isolation for future 5G smartphone applications

A multiband high‐isolation multiple‐input multiple‐output (MIMO) antenna using balanced mode and coupled neutralization line (NL) is presented in this article. The balanced modes of dipole and loop antennas, which leads to good isolation intrinsically are used for the 8 × 8 MIMO in the LTE bands 42 (3400‐3600 MHz)/Chinese 5G band (3300‐3400 and 3400‐3600 MHz). The unbalanced mode of loop antennas, which optimized by decoupling structure are designed for the 4 × 4 MIMO in the LTE band 40 (2300‐2400 MHz). Therefore, the eight‐antenna array is formed by four dipole elements and four loop elements. The simulated and measured results show that the proposed antenna can cover 2300 to 2400 and 3300 to 3600 MHz, with reflection coefficient better than ?6 dB and isolation higher than 15 dB. Good radiation performance and low envelope correlation coefficient can also be obtained. Specific absorption rate of user's hand is also discussed in this article.     

A planar triple band four element antenna system with polarization and pattern diversity for LTE/WLAN/DSRC applications

This paper presents a low profile, triple band antenna system for LTE/WLAN/DSRC applications. It consists of four coplanar waveguide (CPW) fed printed inverted F antennas (PIFAs), each loaded with folded slot antenna (FSA) and folded resonator (FR). The loading of FSA and FR is responsible for the triple band property. An independent/semi‐independent control of each band is observed. Each radiating element is aligned perpendicularly to its adjacent element to employ polarization and pattern diversity. This helps in sustaining a good isolation level in between them without using any additional decoupling networks. The antenna has been fabricated and measured to validate the simulated results. Measurement reveals three 10 dB return loss bandwidths in the ranges 2.47‐2.62 GHz, 3.39‐3.64 GHz, and 5.74‐6.25 GHz, respectively. The isolation levels between the radiators are more than 20 dB at all three operating bands. Respective peak gains are 3.8 dB, 4.5 dB, and 5.3 dB. To gratify the requirement of the diversity performance, some essential attributes like Total Active Reflection Coefficient (TARC), Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Mean Effective Gain (MEG), and Channel Capacity Loss (CCL) are also evaluated.     

A dual‐polarized cross‐dipole antenna with wide beam and high isolation for base station

In this paper, a dual‐polarized cross‐dipole antenna with wide beam and high isolation is designed and analyzed for base station. The proposed antenna consists of two planar cross dipoles with four square patches, two L‐shaped microstrip lines, two ground plates, four parasitic patches, and a reflector. The square patches are placed between the center of cross dipoles to couple with L‐shaped microstrip lines. By introducing the parasitic patches, the wide beam can be realized. The measured results show that the proposed antenna achieves an impedance bandwidth (|S₁₁| < ?10 dB) of about 18.7% (1.9‐2.35 GHz) and an isolation better than 30 dB. A measured gain of 5.7 dBi and a half‐power beamwidth over 120° at the center frequency are obtained. Furthermore, the size of the proposed antenna is only 0.5λ₀ × 0.5λ₀ × 0.22λ₀ (λ₀ is wavelength at the center frequency).     

A hexa‐band dual‐sense circularly polarized antenna for WLAN/Wi‐MAX/SDARS and C‐band applications

In this article, a compact single fed hexa‐band circularly polarized (CP) monopole antenna using split ring resonators (SRRs) on the partial ground plane is designed and experimentally investigated. The loaded SRR elements generate multiple circularly polarized bands along with a reduction in antenna size. The multiband can be controlled by changing the configuration of SRRs and their position on the ground plane without altering the monopole radiator. To illustrate the CP mechanism and multiband operation of the proposed configuration, the surface current density has been studied. The antenna is fabricated on RT Duroid 5880 substrate of permittivity 2.2 with a total size of 47 × 40 × 1.57 mm³. Compared with the existing antenna designs, the proposed structure is compact and demonstrates improved multiband performance with circular polarization.     

Three‐dimensional cylindrical design multiple‐input‐multiple‐output/diversity antenna with high isolation for wireless communication applications

In this article, a three‐port nonplanar multiple‐input‐multiple‐output/diversity antenna with very high isolation between the radiating elements is presented. To realize diversity from the proposed three‐dimensional (3‐D) antenna configuration, three monopole radiating elements are arranged at an angle of 120°. The isolation between the radiators is enhanced by using a multilayered cylindrical decoupling structure and defected ground structure (DGS). The DGS reduces the coupling due to surface waves while the cylindrical decoupling structure reduces the coupling due to space waves. The proposed antenna offers consistent pervasive connectivity in the wireless communication environment due to its 3‐D geometry with multiple radiating elements and good diversity performance. The prototype is fabricated and measured result shows that more than 42 dB isolation is obtained at the center frequency 1.45 GHz. An increment of 1.2 dBi in the antenna gain is also achieved by using DGS and decoupling structure arrangement. The proposed antenna can be easily placed inside the cylindrical housing or it can be integrated with the existing electronics chip, thus nullifying the requirement for dedicated location in the system.     

Design and analysis of on-demand reconfigurable WiMAX/WLAN high isolation 2 × 2 MIMO antenna oriented adjacent/orthogonally for imaging applications in UWB-X band

In this reported work, two dual notched bands from 3.39 GHz to 3.92 GHz and from 4.43 GHz to 5.48 GHz for the WiMAX band (3.3–3.8 GHz) and for (lower) WLAN band (5.15–5.35 GHz) MIMO antenna with adjacent/orthogonal orientations has been investigated. Also, the proposed antenna is capable of controlling these notched bands whenever the need for power saving arises by reconfiguring them using PIN diodes. The issue of isolation between the radiating elements has been overcome by placing the radiating structures in the adjacent and orthogonal arrangement. The proposed antenna is characterized proving an average gain of 4.15/4.37 dBi and maximum radiation efficiency of 91/87% for adjacent/orthogonal orientation. The proposed antenna also shows good agreement with simulated and measured impedance bandwidth, diversity performances in terms of ECC, DG, TARC, and CCL for which values are well below the permissible range.