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.     

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.     

Compact triple‐band stacked monopole antenna for USB dongle applications

In this article, a novel compact triple‐band stacked monopole antenna for USB dongle applications is proposed. The antenna consists of an e‐shaped monopole connected directly to the feedline and a square patch‐shaped monopole at another layer connected to feedline by a metallic pin. The e‐shaped monopole is used to obtain WLAN band (2.4‐2.48 GHz) and WiMAX band (3.4‐3.69 GHz). On the other hand, square patch‐shaped monopole is introduced to get WLAN bands (5.15‐5.35 and 5.725‐5.825 GHz) and WiMAX band (5.25‐5.85 GHz). The antenna is compact with the dimension of 17 × 13 mm².     

A miniaturized multi‐wideband Quasi‐Yagi MIMO antenna system

A multi‐band directional multiple‐input–multiple‐output (MIMO) antenna system is presented based on a rectangular loop excited Quasi‐Yagi configuration. A 64% reduction in size is obtained using a rectangular meandered element as well as a small ground plane. The proposed two‐element MIMO antenna system covers the Telemetry L‐band and several LTE/WLAN bands. It has a wide measured bandwidth of 689 MHz (1.897–2.586 GHz) in the desired band centered at 2 GHz, and a measured bandwidth of more than 168 MHz across rest of the bands. The MIMO antenna system has a total size of 45 × 120 × 0.76 mm³, with a single element size of 55 × 60 × 0.76 mm³. The non‐desired back‐lobe radiation which is obtained using a small ground plane, is significantly reduced by using a novel defected ground structure (DGS) as compared with the complex techniques present in literature. The proposed DGS provides a high measured front‐to‐back ratio of 14 dB at 2 GHz and 11 dB in other bands. A maximum measured realized gain of 5.8 dBi is obtained in the desired band using a single parasitic director element. The proposed MIMO antenna system has a minimum measured radiation efficiency of 70%, isolation of 12 dB, and envelope correlation coefficient of 0.098 within all bands which ensures very good MIMO performance.     

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.     

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.     

Dual‐band and enhanced‐isolation MIMO antenna with L‐shaped meta‐rim extended ground stubs for 5G mobile handsets

A novel compact planar dual‐band multiple input multiple output (MIMO) antenna with four radiating elements for 5G mobile communication is proposed. Each radiating element has a planar folded monopole, which is surrounded by L‐shaped meta‐rim extended ground stubs. The compact folded arms act as the main radiating elements, while combined with the L‐shaped meta‐rim stubs, the proposed antenna forms multiple resonances so as to achieve dual‐band coverage. The simulated and measured results show that the proposed antenna has two wide bands of ?6 dB return loss, consisting of 1.6 to 3.6 and 4.1 to 6.1 GHz, respectively. Without any additional isolation structure between the elements, the isolation for the proposed 2 × 2 MIMO antenna in both desired bands can be achieved better than 12 dB. The measured results show that the proposed MIMO antenna with good performance, that is, stable radiation patterns, high efficiencies, low specific absorption ratio (SAR) to human tissues, is suitable for WLAN/LTE, 4G and future 5G mobile phone applications.     

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 WLAN band‐notched compact four element UWB MIMO antenna

A compact four‐element multiple‐input‐multiple‐output (MIMO) antenna for ultra‐wideband (UWB) applications with WLAN band‐notched characteristics is proposed here. The proposed antenna has been designed to operate from 2 to 12 GHz while reject the frequencies between 4.9 to 6.4 GHz. The four antenna elements are placed orthogonal to attain the polarization diversity and high isolation. A thin stub connected to the ground plane is deployed as a LC notch filter to accomplish the rejected WLAN band in each antenna element. The mutual coupling between the adjacent elements is at least 17 dB while it has low indoor and outdoor envelop correlation (<0.45) and high gain with compact size of two boards, each measuring 50 × 25 mm². To validate the concept, the prototype antenna is manufactured and measured. The comparison of the simulation results showed good agreement with the measured results. The low‐profile design and compact size of the proposed MIMO antenna make it a good candidate for diversity applications desired in portable devices operating in the UWB region.     

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 sub‐6 GHz 5G‐multiple‐input‐multiple‐output antenna system with enhanced isolation

A compact two‐element multiple‐input‐multiple‐output (MIMO) antenna system with improved impedance matching and isolation is presented for future sub‐6 GHz 5G applications. The two identical tapered microstrip line fed modified rhombus‐shaped radiating elements are placed in the same orientation at a compact substrate area of 0.24λ₀ × 0.42λ₀ (where, λ₀ at 3.6 GHz) on a shared rectangular ground. A remodeled T‐shaped ground stub is placed between a pair of radiating element to achieve improved impedance bandwidth and isolation. Further, a split U‐shaped stub connected to center of each radiating element to achieve the desired resonant frequency of 3.6 GHz. The proposed antenna covers a ?10 dB operating band of 3.34 to 3.87 GHz (530 MHz) with more than 20 dB isolation between a pair of elements. MIMO performances are also analyzed and experimentally validated. The measured performances of a prototype are found in good agreement with simulated performances. Further, the simulation study is carried out to see the effect of housing and extended ground plane on two‐element MIMO antenna for practical application. An idea of realization of 12‐element MIMO is also studied using the proposed two‐element MIMO antenna.     

Millimeter‐wave antenna with wide‐scan angle radiation characteristics for MIMO applications

A three‐element quasi Yagi‐Uda antenna array with printed metamaterial surface generated from the array of uniplanar capacitively loaded loop (CLL) unit‐cells printed on the substrate operating in the band 25‐30 GHz is proposed. The metamaterial surface is configured to provide a high‐refractive index to tilt the electromagnetic (EM) beam from the two dipole antennas placed opposite to each other. The metamaterial region focuses the rays from the dipole antenna and hence increases the gain of the individual antennas by about 5 dBi. The antenna elements are printed on a 10 mil substrate with a center to center separation of about 0.5 λ ₀ at 28 GHz. The three‐element antenna covers 25‐30 GHz band with measured return loss of 10 dB and isolation greater than 15 dB between all the three ports. The measured gain of about 11 dBi is achieved for all the antenna elements. The three antenna elements radiate in three different directions and cover a radiation scan angle of 64°.     

A compact dual‐band zeroth‐order resonator antenna loaded with meander line inductor

A novel zeroth‐order resonator (ZOR) meta‐material (MTM) antenna with dual‐band is suggested using compound right/left handed transmission line as MTM. In this article, suggested antenna consists of patch through series gap, two meander line inductors, and two circular stubs. The MTM antenna is compact in size which shows dual‐band properties with first band centered at 2.47 GHz (2.05‐2.89 GHz) and second band is centered at 5.9 GHz (3.70‐8.10 GHz) with impedance bandwidth of (S₁₁ < ? 10 dB) 34.69% and 72.45%, respectively. At ZOR mode (2.35 GHz), the suggested antenna has overall dimension of 0.197λ_o × 0.07λ_o × 0.011λ_o with gain of 1.65 dB for ZOR band and 3.35 dB for first positive order resonator band which covers the applications like Bluetooth (2.4 GHZ), TV/Radio/Data (3.700‐6.425 GHz), WLAN (5‐5.16 GHz), C band frequencies (5.15‐5.35, 5.47‐5.725, or 5.725‐5.875 GHz) and satellite communication (7.25‐7.9 GHz). The radiation patterns of suggested structure are steady during the operating band for which sample antenna has been fabricated and confirmed experimentally. It exhibits novel omnidirectional radiation characteristics in phi = 0° plane with lower cross‐polarization values.     

Ultra‐wideband slot antenna for wireless communication systems

In this article, a new ultra‐wideband rectangular‐slot antenna is proposed and developed for multiband wireless communication systems. The radiating slot is fed by a microstrip line with a microstrip fork‐shaped tuning stub. The frequency characteristic and radiation performance of the proposed antenna are successfully optimized, and a prototype is fabricated and tested. The measured results show that the impedance bandwidth can cover the band from 1.85 to 6.1 GHz with return loss of better than 10 dB, and the corresponding radiation displays omnidirectional patterns across the interested bands. With these frequencies, the proposed structure is especially suitable for applications in wireless communication systems, where a single antenna is needed to operate simultaneously at different bands, such as PCS (1.85–1.99 GHz), UMTS (1.92–2.17 GHz) and all WLAN bands (2.4–2.48 GHz and IEEE802.11a WLAN applications at 5.15–5.35 GHz and 5.725–5.825 GHz). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Compact microstrip antennas with very wide ARBW and triple circularly polarized bands

This article presents two compact circularly polarized microstrip antennas with a very wide 3 dB axial ratio bandwidth and triple circularly polarized bands. A hexagonal stub (circular polarization element) along with tuning element in the ground plane is used for achieving wide 3 dB ARBW in antenna‐1, while a novel approach of using a parasitic strip around the circular polarization element is used in antenna‐2 for introducing band elimination notches in the circularly polarized band of antenna‐1. The antenna‐1 has a ?10 dB impedance bandwidth of 12.34% (3.8‐4.3 GHz), 84.02% (4.9‐12 GHz), and 3 dB ARBW of 79.94% (4.9‐10.9 GHz). The antenna‐2 displays circularly polarized band elimination notch characteristics with ?10 dB impedance bandwidth of 24.80% (3.85‐4.94 GHz), 31.72% (6.1‐8.4 GHz), 25.35% (9.3‐12 GHz), and 3 dB ARBW of 4.84% (4.63‐4.86 GHz), 19.08% (6.02‐7.29 GHz), and 5.7% (9.54‐10.1 GHz). Both the antennas are designed and fabricated on FR4 substrate of dimension (0.52 × 0.52 × 0.04)λ₀ at a frequency of 7.9 GHz.     

Compact dual wide‐band four/eight elements MIMO antenna for WLAN applications

A compact four and eight elements multiple‐input‐multiple‐output (MIMO) antenna designed for WLAN applications is presented in this article. The antenna operates in IEEE 802.11b/g WLAN (2.4 GHz), IEEE 802.11 ac/n WLAN (5.2 and 5.8 GHz) and WiMAX (5.8 GHz) bands. The resonated mode of the antenna is achieved by two unequal Reverse‐L shaped, line‐shaped slots on top and parasitic element on the ground layer. The single antenna provides wide bandwidth of about 29% (2.3‐3.1 GHz) in lower and 22% (4.9‐6.1 GHz) in the upper band. The compactness of the single element antenna is found about 95% with respect to the patch and 61% in overall dimension. Thereafter an investigation is carried out to design two, four, and eight elements MIMO antennas. All of the multi‐element structures provide compact configuration and cover entire WLAN frequency ranges (2.4‐2.48 and 5.15‐5.85 GHz). The dimension of the proposed eight element MIMO antenna is 102 × 52 × 1.6 mm³. It covers the frequency (measured) from 2.4 to 3.1 GHz and 5 to 6.1 GHz. The diversity performance of the proposed MIMO antenna is also assessed in terms of the envelope correlation coefficient (ECC), diversity gain (DG), and total active reflection co‐efficient (TARC). The ECC is found <0.5 whereas the DG >9.0 is obtained for the desired bands.     

Design of a compact protrudent‐shaped ultra‐wideband multiple‐input‐multiple‐output/diversity antenna with band‐rejection capability

In this endeavor, a new multiple‐input‐multiple‐output antenna with a sharp rejection at wireless local area network (WLAN) band is designed and practically examined for portable wireless ultra‐wideband applications. The intended diversity antenna possess a small size of 15 mm × 26 mm and two inverted L‐strip are loaded over the conventional rectangular patch antenna to form protrudent‐shaped radiator that acts as a radiating element. The sharp band‐rejection capability at WLAN is established by incising the L‐shaped slits at the decoupling structure. More than ?21 dB isolation is accomplished for the complete working band (ie, 2.87 ‐17 GHz). Degradation in the antenna efficiency at the center frequency of band rejection corroborates the good interference rejection capability. The working capabilities of the intended antenna are tested by using the isolation between the ports, total efficiency, gain, envelope correlation coefficient, radiation pattern, mean effective gain, and total active reflection coefficient.     

Modified ground with 50 Ω step fed WLAN notch 2 × 2 MIMO UWB antenna

In this research paper, an optimized 2 × 2 MIMO UWB antenna (antenna‐E) with half circled radiators as well as 50 Ω step fed has been introduced. The proposed UWB MIMO antenna has been evolved from recent peer published papers that provide WLAN notch (5.15‐5.85GHz), ultra wide band width (3.1‐10.6 GHz) and again a very good isolation (?20 dB) also maintained. In this paper the evolutions have been derived from antenna‐A to antenna‐E. The Ultra wide band is achieved by using step feed line, cutting a metal strip on a partial ground plane, a rectangular slot underneath the feed line of each radiator in antenna‐E. A high isolation (?20 dB) is obtained by introducing two inverted Г shaped stubs in the ground plane. Both antenna‐D and antenna‐E maintain high isolation (?20 dB). But antenna‐E performs better isolation compared to antenna‐D. The notch at WLAN band (5.15‐5.85GHz) is achieved by etching rectangular C‐shaped slot on the both the radiators. In antenna‐E two radiators are placed horizontally where as in antenna‐D two radiators placed orthogonally. It has been observed that the dimension of final outcome (antenna‐E) is reduced by 33% compared to antenna‐D without compromising the overall performance of the antenna.     

Offset planar MIMO antenna for omnidirectional radiation patterns

An offset quad element multi‐band planar MIMO antenna with omnidirectional radiation patterns is proposed for nonline of site (NLOS) communication on low‐cost FR‐4 dielectric substrate for 4G and future technologies. A 1 × 2 power divider arm results in dual beam and enhances diversity parameters and omnidirectional radiation patterns. Moreover, the MIMO antenna limits the proximity/coupling effects using a T‐shaped isolator and achieves more than 12.4 dB of isolation between the radiating ports. The proposed design covers WLAN/WiMAX bands with gain and radiation efficiency of more than 2.6 dBi and 71%, respectively, in 2:1 VSWR bands of bandwidths 16.39% (2.24‐2.64 GHz) and 7.88% (3.41‐3.69 GHz). The ?10 dB impedance bandwidth is more than 280 MHz in each band. An ECC level of ≤ 0.01 has been achieved in the whole band.     

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.