GHz WLAN Band Research Articles

An inverted U‐shaped merged stubs hexa‐band 4‐element MIMO antenna for advanced wireless applications

SummaryA four‐element hexa‐band inverted U‐shaped merged stubs miniaturized Multiple‐Input Multiple‐Output (MIMO) radiator, operating in 2.10–2.17 GHz for 3G (2.17 GHz) band, 2.52–2.60 GHz for 4G (2.5 GHz) band, 3.31–3.46 GHz for 5G (3.4 GHz [n77 and n78]) bands, 3.66–3.72 GHz for 5G (3.7 GHz [n77 and n78]) bands, 4.53–4.62 GHz for 5G (4.5 GHz [n79]) band, and 5.15–6.02 GHz for 5.5 GHz WLAN bands, is developed. The radiator and ground planes comprise of multiple inverted U‐shaped stubs and slots to form the proposed configuration having overall compact dimensions of 62 × 62 × 1.6 mm3. The peak gain and radiation efficiency of the antenna are found to be 1.31 dBi and 77.48% at 2.17 GHz, 0.98 dBi and 63.3% at 2.55 GHz, 2.9 dBi and 71.13% at 3.38GHz, 1.6 dBi and 66.68% at 3.68 GHz, 2.58 dBi and 77% at 4.57 GHz, and 3.27 dBi and 68.68% at 5.52GHz. The arrangement of four antenna elements is orthogonal (rotationally symmetric) to minimize the mutual coupling, and hence, a minimum isolation of more than 15 dB is noted between all the antenna ports. Furthermore, Envelope Correlation‐Coefficient (ECC) in desired bands is lower than 0.012. Channel Capacity‐Loss (CCL) and Diversity‐Gain (DG) are also good with 0.015 bits/s/Hz and 9.96 dB, respectively. The fabricated structure measurement results agree well with simulation outcomes. These facts result that the proposed MIMO structure is a promising module for the usage in WLAN, 4G, and 5G band applications.

A Decoupling method using Split Ring Resonator (SRR) for Tri-band MIMO Antenna for WLAN LTE Band and 5G applications

MIMO antenna design has always been a topic of interest in wireless technology. Although it has many benefits, the key challenge is to minimize mutual coupling between antenna elements. This study presents a decoupling technique between two tri-band antennas for LTE, WLAN, and 5G applications. For 3.5GHz, a monopole is initially created; the other two resonant frequencies are produced by changing the partial ground plane. Then, a MIMO antenna system is created using two tri-band monopoles. The resonators of low band can minimize the mutual coupling for two higher bands by suppressing surface wave propagation. Finally, coupling is reduced in the low band by using a Split Ring Resonator (SRR) to cancel out the original coupling. The reported MIMO antenna spans the 2.4/5.8GHz WLAN and LTE bands, as well as the 3.5 GHz 5G bands, with a mutual coupling of less than -18 dB.

A dual-band MIMO PIFA antenna with a printed rectangular open-ended ring for 5G/WLAN mobile terminal

A dual-band 8 × 8 multiple-input-multiple-output (MIMO) PIFA antenna that operates in the sub-6 GHz spectrum for 5G and WLAN mobile terminals is presented. The eight elements of the MIMO antenna are formed by using an L-slotted PIFA antenna, an L-shaped parasitic element, and a 2D rectangular open-ended ring parasitic structure that is printed next to the L-shaped parasitic element. In this article, we first proposed an ultra-thick PIFA antenna element to work in the 3.4-3.8 GHz 5G band and the 5.15-5.85 GHz WLAN band, adopting a new method that can provide dual-band behavior with wide bandwidth. Then, the final antenna element is used to design an eight-port MIMO antenna system, and the results show good MIMO performance in terms of envelope correlation coefficient (ECC), diversity gain (DG), mean effective gain (MEG), and multiplexing efficiency (ME).

A reconfigurable wideband MIMO antenna combines RF energy harvesting

SummaryThis article introduces a novel and groundbreaking approach combining multiple‐input‐multiple‐output (MIMO) technology with radio frequency (RF) energy harvesting. The proposed antenna consists of two semi‐circular monopole antenna components, optimized with dimensions of 89 × 51.02 × 1.6 mm3, that share a common ground plane to achieve MIMO characteristics. A series of split‐ring resonators on the ground plane significantly enhances the isolation between the two radiating components. Band‐notched features are performed in the 3.5 GHz WiMAX and 5.5 GHz WLAN bands through modified C‐shaped slots in the radiating patch and two rectangular split‐ring resonators serving as parasitic devices near the feed line. The reconfiguration of band‐notching is made possible by controlling the modes of the embedded PIN diodes. The two antenna elements maintain mutual coupling below −18 dB from 1.5–13 GHz, achieving an impressive 158.62% impedance bandwidth. The antenna's efficiency and gain experience significant drop, indicating effective interference suppression at the center frequencies of the notch bands, and its performance in MIMO systems is assessed through parameters including envelope correlation coefficient, port isolation, radiation patterns, efficiency, gain, and diversity gain. The simulated properties of the designed antenna closely align with the measured outcomes, demonstrating its reliability and consistency. Moreover, the article evaluates the antenna's potential for RF energy harvesting, achieving a maximum harvested energy of 4.88 V. This proposed antenna can be used in multiple applications, like wideband, band‐notching MIMO, and RF energy harvesting. This proposed antenna is an efficient, reconfigurable wideband MIMO antenna with novel RF energy harvesting capability.

A CRLH-TL Inspired Dual-Band Antenna With Polarization Diversity for Wrist-Worn Wireless Body Area Network Devices

A wrist-worn dual-band smartwatch antenna with polarization diversity is proposed for smartwatches. The antenna has a cylindrical structure with a diameter of 33.6 mm and a height of 6.8 mm. The radiated structure is inspired by composite right/left handed-transmission lines (CRLH-TLs) to realize a dual-band operation (2.4 GHz and 5.8 GHz WLAN band). The unit cell of the CRLH-TL is analyzed, and its equivalent circuit model and the dispersion curves are studied for mode analyzation. The +1 and -1 modes of CRLH TL are employed for dual-band operating, and two orthogonal-polarized modes are excited with different types of feeding structure to realize the polarization diversity with low coupling and low envelope correlation coefficients (ECC). The wrist model is built in both simulation and experiment to evaluate the performance of the antenna, which shows a good radiation and diversity performances. The measured degree of freedom (DoF) is 1.92 and the capacity is 17.39 bit/s/Hz with 30 dB SNR. The results of specific absorption rate (SAR) are also studied and they are pretty low. These characteristics of the proposed antenna make it a competitive candidate for wrist-worn wireless body area network devices.

Highly selective, fractal-configured UWB-FSS for sub-6 GHz 5G, GSM, WLAN, and C band electromagnetic stealth application

AbstractA miniaturized and flexible frequency-selective surface (FSS) has been presented in this article with a unit cell size of 0.049 λc × 0.049 λc where λc is the free space wavelength at the lower cut-off frequency. In order to achieve an ultra-wide (−3 dB) second order pass band of 151.3% with enhanced selectivity factor of 0.887, a cascaded triple layered hybrid resonating structure has been proposed with symmetrical Minkowski island-shaped fractal geometry pair and spiral-shaped middle layer in optimized air gap coupling. Furthermore, 149.8% ultra-wide pass band also ascertains the conformal feature of the proposed structure. In addition to this, the proposed FSS provides the stable angular response for both TE and TM polarization. An equivalent circuit model has been synthesized for accurate frequency response. Finally, a sample prototype has been fabricated to verify the experimental validation. Excellent angular stability under large oblique incident and significant conformal characteristics ensure the compatibility of the proposed structure for electromagnetic stealth in 0.9–1.8 GHz GSM band, 2.10–2.14 GHz wireless medical telemetry band, 2.4–2.5 and 4.9–5.8 GHz WLAN band, 3.4–3.7 and 4.4–4.9 GHz sub-6 GHz 5 G band, and 3.7–4.2 GHz C band.

A Miniaturized, Dual-Port, Multiband MIMO with CSRR DGS for Internet of Things Using WLAN Communication Standards

A compact, dual-port, triband MIMO antenna is designed and tested for three sub-6 GHz WLAN bands for IoT applications. The size and performance of the antenna make it versatile for the emerging IoT applications communicating using the 2.4 GHz, 5.2 GHz, and 5.8 GHz WLAN frequencies. The single radiating element of antenna geometry includes a pair of modified and optimized rectangular patches. A complimentary split ring resonator (CSRR) structure is incorporated in the ground plane as a defect (defected ground structure) to attain the third operational band. The orientation of the elements, orthogonally arranged, along with DGS, enhances the isolation between the radiating elements keeping it below 18 dB throughout the three operating frequency bands. The size of the final antenna is as small as 0.32 λ 0 × 0.32 λ 0 mm2 build on commercially available and cheap FR4 substrate of thickness 1.5748 mm. A peak gain of 7.17 dBi is attained for the proposed MIMO system. This MIMO antenna also satisfies the diversity parameter requirements including DG > 9.8 , ECC < 0.5 , TARC < − 10 dB, and CCL < 0.5 bits/s/Hz. This makes the proposed antenna a good candidate for IoT applications employing WLAN frequencies.

Efficiency-Driven Design for Planar Antennas With Lossy Materials

This article demonstrates a design strategy for improving the radiation efficiency of a planar antenna made of a layered conductor of MXene with modest conductivity on a lossy PDMS substrate. New methods to reduce the conductor loss and the dielectric loss are proposed. On the one hand, the conductor loss is minimized by identifying the location of high current density on the antenna radiator, and then accordingly altering its shape to redistribute the surface currents as uniformly as possible. On the other hand, the dielectric loss is reduced by employing a folded ground plane with elevated edges. This ground plane structure reduces the concentration of the electric field in the dielectric substrate and thus minimizes the power dissipation due to dielectric loss. The improvement techniques are implemented starting from a standard U-slot microstrip antenna. The method demonstrates to improve the radiation efficiency significantly by an average of 14% for a microstrip antenna fabricated using MXene conductor with a sheet resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 {\Omega }$ </tex-math></inline-formula> /square and a lossy PDMS substrate. Importantly, the proposed method can preserve the overall antenna size and the operating frequency band. The optimized antenna exhibits a high radiation efficiency of 71% and offers a wide impedance bandwidth of 56% covering operation for the 5 GHz WLAN band.

AMC-Based Low-Profile Dual-Band Slotted Patch Antenna for IoT Devices in the Healthcare System

An artificial magnetic conductor (AMC)-based patch antenna with a low profile is developed for wireless devices in IoT-based healthcare systems. The proposed antenna comprises two pairs of circular-shaped patches with circular-shaped slots and a dual-band 4 × 4 array of AMC reflectors with two zero-degree reflection responses to enhance the antenna's radiation performance. For the 2.45 GHz ISM and 5.4 GHz WLAN bands, the patch antenna has dimensions of 0.44λ0 × 0.52λ0 × 0.013λ0, with partial ground structures to improve radiation characteristics. Following that, a unique dual-band symmetrical AMC unit cell with dimensions of 22 × 22 × 1.6 mm3 is developed. There is a gap of 15 mm between the antenna and the AMC surface. The antenna is supported by a 4 × 4 AMC array that has a total dimension of 0.72λ0 × 0.72λ0 × 0.15λ0. The reflection coefficient values of less than − 10 dB in the 1.7–2.5 and 5.1–5.6 GHz bands, with a bandwidth percentage of 38 and 9.3%, respectively. The antenna's gains were 7.2 and 4 dBi inside the bands. Furthermore, the Specific Absorption Rate (SAR) value did not match the WHO's safety and health guidelines. The issue was solved by including an AMC surface in the proposed antenna. At 2.45 and 5.4 GHz, SAR values of 0.58 and 1.04 W/Kg were measured. Vector network analyser and anechoic chamber were used to test the performance of antenna and AMC surface prototypes. There is a substantial agreement among measured and simulated parameters of an antenna. Consequently, the developed antenna combination with the AMC structure is suited for wireless devices in ISM and WLAN bands, often used in IoT-based healthcare systems.

A Low-Profile Microstrip Vertically Polarized Endfire Antenna With 360° Beam-Scanning and High Beam-Shaping Capability

A novel low-profile vertically polarized planar endfire smart antenna that can achieve 360° beam-steering and high beam-shaping capability is proposed. The microstrip antenna is printed on a single thin substrate with a vertically polarized omnidirectional driven source and 36 tunable slot-integrated microstrip vertically polarized resonators (SMVR) for shaping the endfire beams. To verify the design approach, a prototype operating at the 5 GHz WLAN band is fabricated and tested. The results show that the antenna operates from 5.55 to 5.75 GHz and is capable of scanning a single endfire beam from 0° to 360° in the full azimuth plane. The scanning resolution and the maximum realized gain are 15° and 8.2 dBi, respectively. Moreover, multiple radiation pattern shapes including omnidirectional beam, dual-beams, and tri-beams can also be generated by the antenna. The overall antenna height is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.06~\lambda $ </tex-math></inline-formula> at 5.6 GHz. This design provides a new antenna configuration for low-profile vertically polarized endfire beam-steering and beam-shaping antenna and is promising for future wireless communication systems with lost-cost beamforming property.

Parasitic element loaded efficient electrically small antenna for indoor wireless applications

AbstractThis study presents an electrically small antenna loaded with a parasitic loop resonator for dual‐band operations. The proposed configuration covers 2.4 GHz Bluetooth/Wi‐Fi, 5G new radio (n79), and 5 GHz WLAN bands. In this study, a coplanar waveguide (CPW) feed L‐shaped driven element is capacitively coupled with a parasitic loop resonator to get a dual‐band response centered at 2.43 and 5.5 GHz, respectively. Further, an open‐ended stub is attached with the driven element to achieve wide impedance bandwidth over the 5 GHz WLAN band. The overall dimension of the proposed antenna is 0.06λ × 0.2λ, where λ is the wavelength at 2.43 GHz. The parasitic loop resonator loaded electrically small antenna offers 60 and 1580 MHz impedance bandwidth (S11 &lt; −10 dB). The stable impedance bandwidth and radiation characteristics of the proposed antenna validate its suitability for wireless application(s).

A compact double-inverted Ω-shaped dual-band patch antenna for WLAN/WiMAX applications

Abstract In this study, a new compact dual-band antenna with overall size of 11 × 14.46 × 1.6 mm3 has been designed, fabricated and tested. The proposed antenna consists of two inverted Ω-shaped strips loaded with two different comb structures. The fist comb of six elements connected to the first Ω-shaped radiating branch is used to decrease the second band lower cut-off frequency and cover the intended WLAN and WiMAX applications. In order to cover the 2.45 GHz WLAN band and further reduce the antenna dimensions, a second comb structure of 14 elements is attached to the upper radiating branch. The fabricated antenna covers the frequency bands from 2.42 to 2.6 GHz and from 4.25 to 6.77 GHz with a reflection coefficient of |S 11| ≤ −10 dB. The antenna shows an omnidirectional radiation pattern in the H-plane and a monopole-like radiation pattern in the E-plane. The measured results agree well with the simulated ones which indicate that the proposed antenna is suitable to be used in the WLAN/WiMAX applications.

A Wideband Hybrid Fractal Ring Antenna for WLAN Applications

We propose the design of a novel fractal antenna that is both unique and performance-driven. Two important antenna design features, miniaturization and wideband operation, are combined in this work. A ring-shaped antenna is designed using the well-known fractal geometry. This hybrid geometry is a fusion of meander and Koch curve shapes. The geometrical construction of the proposed antenna is compared to the standard Koch curve geometry. It is shown that combining the meander and Koch curve shapes increases the effective electrical length. The wider bandwidth is achieved by bringing the higher modes together. The overall dimensions of proposed meander Koch curve fractal ring antenna are 45 × 25 × 1.6 mm3. The resonance frequency of the antenna is between 4.94 and 6.12 GHz (% BW = 21.83), which covers the entire 5 GHz WLAN band. The prototype has been fabricated and experimentally verified.

Travelling Wave Antenna Based MIMO for 5GHz WLAN Band Application With Pattern Diversity

ABSTRACT A single-layer, four-element multiple-input-multiple-output (MIMO) antenna for 5 GHz (5150–5850 MHz) band WLAN application is proposed. Each unit element consists of three sections and this behaves as a travelling wave antenna, which enables frequency scanning feature. The combination of orthogonal feeds and placement of elements introduce dual-polarisation, and pattern diversity respectively. Thus, the proposed MIMO antenna offers a higher degree of freedom (pattern diversity, frequency scanning and dual polarisation), which makes it exceptional. The proposed MIMO antenna has a maximum impedance bandwidth of 17% (4.93–5.87 GHz) corresponding to port 4 and isolation of 17.5 dB, which is achieved without additional decoupling/isolation enhancement circuits. The envelope correlation coefficient of 0.25, capacity loss less than 0.4 bits/sec/Hz, and the mean effective gain (MEG) ratio of 0 dB in the desired frequency band quantifies the diversity performance for WLAN applications. The proposed MIMO has gain from 2 to 5.5 dB and occupies a compact volume of 1.3 λ × 1.3 λ × 0.02 λ mm3, which may be one of the most miniaturised electrical configurations.

Dual-Band Frequency Absorber Based on Split-Ring Resonators for WiMAX and WLAN Bands

In this paper, a dual-band compact absorber design based on split-ring resonator for WiMAX and WLAN bands is presented. Top plate of a unit cell in the proposed design is composed of three concentric circular split ring (SR) elements covers an area of π×13.42 mm2 and placed on a FR4 substrate with 1.5 mm thickness, dielectric constant of 4.3 and loss tangent of 0.025. Also, six miniature metallic loadings are appropriately inserted between the SR elements. The back side of the substrate is covered full ground plane for shielding transmission from port 1 to port 2. In the design, SR elements are primary resonator of the proposed absorber and provide a dual band of absorption at the respective frequencies. The metallic loadings are used for fine frequency tuning where the absorption peaks occur. Hence, the absorption frequency of the design can be easily tuned by means of sliding the loadings between the rings without changing any design parameters. The proposed compact absorber excited by incident electromagnetic wave provides 0.92 and 0.97 absorption peaks at 3.52 GHz WiMAX and 5.16 GHz WLAN bands, respectively. The design and analysis of the absorber are performed by means of CST Microwave Studio based on frequency domain solver. In this paper, the absorber design with novel configuration is introduced in detail and its corresponding electric field distributions and absorption characteristics at the related bands are presented. Also, the proposed SRR-based absorber design is compared with the previously reported dual or multi bands absorbers in terms of dimensions, resonance frequencies and number of bands.

Wideband antenna pair and its applications for 5G metal frame mobile phones

A wideband antenna pair used for 5G mobile phones is proposed in this paper. Both elements of the antenna pair consisting of an open slot and a coupled feeding line can cover the band of 3.3–6 GHz, and the isolation is larger than 10 dB. The ground clearance and the total size are 1.5 mm and 30 mm × 1.5 mm × 7 mm, respectively. Using the antenna pair, four- and eight-element multiple-input–multiple-output (MIMO) antennas are constructed. The simulated results show that the proposed antenna pair can be used to construct MIMO antennas for 5G metal frame mobile phones. As an example, the four-element MIMO antenna is manufactured and tested. The measured results show that the four elements can cover the band of 3.3–6 GHz, and the n77, n78, n79, and 5 GHz WLAN bands are covered. At the working bands, the measured efficiencies and isolations are bigger than 46% and 11.4 dB, respectively.

A miniaturized reconfigurable unlicensed ultra‐wideband antenna with multiple band‐notch performance

This paper presents a compact reconfigurable ultra-wideband antenna with multiple band-notch characteristic. The truncated corners in the rectangular patch are employed to realize the desired ultra-wideband (UWB) operation. The band-notch property in the 3.5 GHz WiMAX and 5.2 GHz WLAN bands are obtained by the conventional C-shaped slots in the radiating patch, and the band-notch performance in the 7.5 GHz X-band is especially realized by introducing a parasitic meandering strip beneath the ground. The reconfigurable band-notch function is achieved by controlling the states of the PIN diodes inserted in the band-notch structures. The overall dimension of the antenna is 19.5 mm × 14 mm. The simulation and experiment results confirm that the antenna can switch between a UWB state, three single band-notch states, three dual band-notch states and a triple band-notch state. Moreover, stable radiation patterns are exhibited.

Compact Bioinspired Antenna for WLAN 5 GHz Application

This paper presents the development of a compact monopole antenna bioinspired in the Opuntia ficus-indica plant-shape, generated by Gielis formula, built in fiberglass substrate, with hybrid feed by transmission line and probe, for wireless local area network band at 5 GHz. By using the plan-shape, it is possible to increase the perimeter of the design and thus reduce its total area, which can be employed in the development of compact antennas with larger electrical length. Results of the bioinspired plant-shape antenna is compared to the square-shape antenna, and the proposed antenna presents a more compact structure, with a reduction of 62.5% in the total area, with a value of 108.4 mm2, narrower bandwidth, and a directive radiation pattern, with a bandwidth of 1.44 GHz (4.41–5.85 GHz), which covers the 5 GHz WLAN band (5.15–5.85 GHz) and measured gain of 2.6 dBi, at the resonance frequency.

High efficient dual band stacked antennas integrated into rescue helmets for indoor communication

AbstractA dual-band stacked antenna integrated with a rescue helmet is proposed for WLAN applications. The cross slot aperture feeding technique enables the antenna to support dual-band operation at 2.4 and 5 GHz. On the ground plane, two slots are formed, perpendicular to each other and of different lengths. Four dielectric layers of different permittivity are stacked over this cross slot to attain the desired frequency bands. Under free space condition, the radiator yields 7% (2.31–2.48 GHz), 15.87% (5.12–6 GHz) 10 dB return loss bandwidth (BW). The use of low loss dielectric layers on the slots also provides a high antenna efficiency and moderate gain at both frequency bands. The small dimension of antenna encourages its use as a wearable helmet antenna. Antenna performances are observed under wearable condition. For assessing human exposure to RF electromagnetic fields, SAR evaluations are conducted at both 2.4 and 5 GHz WLAN bands.

Isolation Improvement between Closely-Spaced Antennas Using EBG

Isolation improvement between two closely spaced antennas using a single column EBG is proposed for compact wireless devices. The proposed design developed for the 2.4 GHz WLAN band achieves more than 17 dB isolation improvement between two planar inverted-F antennas (PIFAs) compared to the no-EBG case. As a result, improved MIMO capacity is also achieved. The proposed design can be scaled up or down in frequency and may be implemented for small devices such as, smart watches, Wi-Fi routers, internet of things (IoT) devices etc.