GHz WLAN Band Research Articles

Circularly Polarized MIMO Dielectric Resonator Antenna With Reduced Mutual Coupling

A circularly polarized (CP) multiple-input-multiple-output (MIMO) antenna is investigated. This MIMO antenna consists of two identical dielectric resonator antennas (DRAs), which use the same feeding cross slots to generate the same CP fields. Four metal strips are printed on the lateral sides of each DRA to change the rotation direction of the E-field coupled in the passive (coupled) DRA, vary its polarization property, and thus make it opposite (orthogonal) to that of the active (driven) DRA. Thanks to the polarization orthogonality, the isolation between the two CP DRAs is improved significantly, without occupying extra space and destroying the antenna performance. In addition, using this decoupling scheme, the two CP DRAs can operate not only separately but also simultaneously. For verification, a prototype operating at the 2.4 GHz WLAN band is fabricated and measured. In the operating band (2.38-2.52 GHz), the MIMO antenna obtains a maximum improvement of 31 dB and an average improvement of 11 dB in isolation, at a center-to-center distance of 0.4λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> .

Wideband Flexible/Transparent Connected-Ground MIMO Antennas for Sub-6 GHz 5G and WLAN Applications

A flexible transparent wideband four-element MIMO antenna with a connected ground plane is proposed with numerical computation and experimental measurement studies. The optical transparency is obtained using flexible conductive oxide material AgHT-4 and Melinex substrate. The radiating elements are in the form of circular stub-loaded C-shaped resonators, which are positioned in a carefully structured flexible Melinex substrate with an interconnected partial ground plane structured in the form of an L-shaped resonator, attaining an overall antenna size of 0.33λ × 0.48λ at the lowest operating frequency. The proposed antenna spans over a.10 dB impedance bandwidth of 2.21-6 GHz (92.32%) with an isolation level greater than 15dB among all elements. The maximum gain is 0.53dBi with a minimum efficiency of 41%, respectively which is satisfactory considering flexible structure and sheet impedance of 4Ω/sq. MIMO antenna parameters in terms of the envelope correlation coefficient (ECC) and diversity gain (DG) are also extracted where all the values are satisfactory for MIMO applications. The bending analysis of the proposed transparent MIMO antenna along the X and Y axis has revealed good performance in terms of scattering parameters and radiation pattern along with MIMO diversity performance. All of these technical points make the flexible MIMO antenna suitable for smart devices using sub-6 GHz 5G and WLAN band in IoT applications where visual clutter and co-site location issues need to be mitigated with the integration ease of conformal placement on the curved component/device surfaces.

Wideband Four-Port MIMO antenna array with high isolation for future wireless systems

A four-port MIMO antenna array with wideband and high isolation characteristics for imminent wireless systems functioning in 5G New Radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN bands is proposed. Each array antenna element is a microstrip-line fed monopole type. The novelty of the antenna lies in loading an “EL” slot into the radiating element along with two identical stubs coupled to the partial ground in order to improve the impedance matching and radiation characteristics across the bands of interest. To further attain high port isolation without affecting the compactness and radiation performance of each antenna element, the technique of introducing an innovative un-protruded multi-slot (UPMS) isolating element (of low-profile 2 × 19 mm2) between two closely spaced antenna elements (with an edge-to-edge distance of approx. 0.03λ at 4.6 GHz) is also presented. Besides demonstrating a small footprint of 30 × 40 × 1.6 mm3, the proposed four-port MIMO antenna array has also shown wide 10-dB impedance bandwidth of 58.56% (3.20–5.85 GHz), high isolation of more than 17.5 dB, and good gain and efficiency of around 3.5 dBi and 85%, respectively, across the bands of interest. Finally, the MIMO performance metrics of the proposed antenna are also analyzed.

Compact, Isolation Enhanced, Band-Notched SWB–MIMO Antenna Suited for Wireless Personal Communications

Herein, a Conductor Backed Co-Planar Waveguide fed, compact, slotted Multiple–Input–Multiple–Output or MIMO antenna having Super Wideband (SWB) response and tunable band-notching feature is presented. In addition, an improved method for cut-off frequency prediction of the antenna is formulated. A super wide frequency response from 01.21 to 34.0 GHz and notches at Wireless Local Area Networks or WLAN bands (04.92–05.83 GHz) and Worldwide Inter-operability for Microwave Access or WiMAX bands (03.30 GHz–03.70 GHz) are obtained. By fine tuning the dimensions of the Split Ring Resonator Structure introduced in the radiating element, band-notched characteristics centered at 05.50 GHz WLAN band is obtained. A second band notch having centre frequency at 03.50 GHz for the WiMAX band is obtained by the introduction of a Spiral Microstrip Defected Structure in the feeding segment. The antenna is 20 × 36 × 1 mm3 in dimension. Acceptable gain all through the functional bandwidth, excepting the notched bands makes the MIMO antenna a novel contender for SWB operations particularly for Wireless Personal Communications.

Characteristic Mode Analysis of a Nonuniform Metasurface Antenna for Wearable Applications

A novel nonuniform metasurface antenna is designed based on the characteristic mode analysis for wearable applications. A metasurface layer consists of a 3 × 3 unit cell array, in which the center and corner cells are rotated counterclockwise, whereas the other four unit cells are rotated in the opposite direction with a same rotation angle. The structure of a nonuniform metasurface is optimized according to the modal significance curves and surface currents, which resulted that mode 1 and mode 2 are combined to widen the bandwidth, which can cover the 5 GHz WLAN band. The volume of the proposed antenna is equal to a cylinder with a diameter of 55 mm and a thickness of 4 mm. The measured efficiency is greater than 80% and the average gain can achieve 7.63 dBi in the working band. The proposed antenna is harmless to human body, which can be evidenced by the simulated 1 and 10 g averaged specific absorption rate values.

Enhancing isolation and bandwidth in planar monopole multiple antennas using thin inductive line resonator

This paper presents efficient mutual coupling reduction and bandwidth enhancement method in planar monopole multiple antennas. High isolation and bandwidth extension are achieved by integrating a thin inductive line resonator as reflector and parasitic element between the antenna elements. A 36.9% bandwidth (4.69–6.5 GHz) is achieved at 4.9 GHz, which encompasses the sub-6 GHz (4.8–5.0 GHz) 5G and 5.15–5.85 GHz WLAN bands. The thin inductive line resonator provides an effective means of controlling the electromagnetic wave propagation. Approximately 45 dB isolation and 4.9 dB maximum gain can be achieved between two parallel monopole antennas with 0.36λ0 spacing. The physical meaning of electromagnetic propagation in MIMO antenna is studied by discussing the coupling mode between antennas and the working mechanism of thin inductive line as parasitic elements and reflectors. Furthermore, a four-element antenna with orthogonal polarization diversity is also proposed based on the thin inductive line. Correlation coefficients (CC) are well below 0.05 across the operating bandwidth.

Dual‐polarised high‐gain triple‐band differential antenna for WLAN and Sub‐6 GHz 5G applications

A new dual-polarised high-gain triple-band differential-fed antenna is proposed in this study. The antenna adopts a differential feeding scheme, in which a high-frequency radiator for 3.5 GHz Sub-6 GHz 5G band and 5 GHz WLAN band, and two pairs of low-frequency radiators for 2.45 GHz WLAN band are effectively combined to obtain multiband operation. To filter out unwanted frequency band, four half-wavelength slots are introduced to generate a notch band between 3.8 and 4.8 GHz. Experimental results show that the proposed antenna achieves 10-dB impedance bandwidths of 2.37-2.61 GHz for the low-frequency band, 3.27-3.76 GHz for the intermediate frequency band, and 4.87-5.98 GHz for the high-frequency band. The gains of the antenna are all above 8.0 dBi for all the three bands. The antenna exhibits a good directivity and low cross-polarisation level (below -20 dB); thus it is a good candidate for WLAN and Sub-6 GHz 5G wireless access point systems.

Compact dual band‐notched UWB multiple‐input multiple‐output antenna for portable applications

AbstractA compact ultra‐wideband (UWB) multiple‐input multiple‐output (MIMO) antenna with dual band‐notched characteristics for portable applications is proposed in this article. The antenna is fed by coplanar waveguide and has four feeding ports with the size of 50 × 50 mm2. By etching split‐ring resonator slots on the radiation patches, dual notches filtering out the 3.5 GHz WiMAX and 5.5 GHz WLAN bands can be achieved. The design process is given step‐by‐step and the band‐notched mechanism is studied with the surface current distributions. Moreover, the band‐notched characteristics of cylindrical conformal antenna is analyzed in this article. The experimental results show that the proposed antenna can be widely used in UWB communication system with good radiation characteristics, stable gain, and low envelope correlation coefficient. The idea embodied in this article can also be used to guide for the research of band‐notched conformal UWB MIMO antenna.

Wideband WLAN Mimo Antenna for Smart Cities

The MIMO technology fulfils the present demand of higher data rate and capacity in smart cities. The single antenna in a transmitter and receiver system has low data rate and some reliabilities issues which can be easily solved by the use of multiple antenna wireless technology. The connectivity issue also creates problem in smart cities due to large users. The use of MIMO technology has significant advantages which fulfils all the present needs of wireless technology. In this paper a wideband MIMO antenna has been designed which covers 4.59-5.68 GHz WLAN band. The MIMO antenna resonates at 5.14 GHz and produced 1 GHz of bandwidth. The overall size of the antenna is 32 x 20 mm2. FR4 material is chosen for substrate and PEC material is considered for radiator and ground of MIMO antenna. The proposed antenna has isolation of less than -11.8 dB in the entire proposed frequency band. The proposed MIMO antenna gain of 2.59 dBi and directivity of 3 dBi was obtained. The ECC of less than 0.015 is observed in the frequency band while at resonant frequency 5.14 GHz it was 0.0002. The other antenna performance parameters for MIMO antenna were also discussed

A compact broadband differential‐fed microstrip patch antenna with 5.8 GHz WLAN band‐notched under quad‐mode resonance

AbstractA compact broadband differential‐fed microstrip patch antenna with 5.8 GHz WLAN band‐notched under quad‐mode resonance is proposed in this article. The antenna consists of two hybrid shape radiation patches and a pair of capacitances loaded loop (CLL) resonators. The broadband performance is achieved by integrating TM10 and TM01 radiation modes of rectangular patches and TM1,0,−1 radiation mode of triangular patches. Then these three radiation modes are adjusted close to each other to form a wide operation band. After that, with the loading of CLL resonators, a nonradiative resonant mode is introduced. Thus, the low‐frequency band of the proposed antenna can be further expanded, and a frequency notch point is introduced in 5.8 GHz WLAN band. Finally, the proposed antenna is fabricated and measured. The measured impedance bandwidth is about 43.5% (5.93‐9.23 GHz) while keeping a compact structure without any air gaps. Additionally, the broadside gain is varied from 4 to 6 dBi with a notch point at 5.8 GHz.

Wideband Circularly Polarized Planer Inverted-F Antenna using Reactive Impedance Surface

A wideband circularly polarized (CP) planar inverted-F antenna (PIFA) is proposed and designed using reactive impedance surface (RIS) for mobile communication. PIFA with RIS is used for CP radiation, size reduction and wideband of the proposed CP-PIFA. It is a different technique for improving the various performance parameters of the antenna, that is, narrow bandwidth, size reduction, and the axial ratio (AR). The structure of circular polarized PIFA is designed, analyzed, geometrically optimized, and implementation of the antenna to operate at 2.4 GHz WLAN bands. Finally, a proposed CP-PIFA is analyzed and simulated using full 3D electromagnetic high-frequency structure simulator (HFSS). The measured impedance bandwidth of designing an antenna (S11) 10-dB is 1399 MHz (1.542-2.943 GHz) 58.29\%, simulated 3-dB axial ratio bandwidth is 870 MHz (1.639-2.50 GHz) 36.25\%, measured voltage standing wave ratio (VSWR) is 1.02 and the realized gain is 8.1 dB for the 2.4 GHz WLAN bands.

Circularly polarized ACPW Fed CRLH-TL based ZOR antenna with band notch characteristics

AbstractIn this paper, two asymmetric co-planar waveguide (ACPW) fed circularly polarized (CP) zeroth-order resonance (ZOR) antennas (Antenna I and II) are presented using a composite right and left-handed transmission line (CRLH-TL) approach. By adding a stub on the left side of the ACPW ground and adjusting its length, circularly polarization property has been achieved in Antenna I. The simulated 3 dB axial ratio bandwidth (ARBW) of Antenna I is 1750 MHz (3.50–5.25 GHz). Next, the left side ground plane of Antenna I is further defected by etching a quarter wavelength slit to introduce a notch band (Antenna II). Antenna II has an extended 10 dB return loss bandwidth of 2200 MHz (3.28–5.48 GHz) with a band notch from 4.18–4.65 GHz that isolates the WiMAX and 5.2 GHz WLAN bands. ARBWs of 1080 and 870 MHz are achieved in the first and second band of Antenna II. The overlapping 3 dB ARBW and 10 dB return loss bandwidths of Antenna II in these two bands are 770 and 830 MHz, respectively.

Characteristic mode analysis applied to reduce the mutual coupling of a four‐element patch MIMO antenna using a defected ground structure

A multiple-input-multiple-output (MIMO) microstrip patch antenna array of four elements is proposed to cover the 5.8 GHz WLAN band. The characteristic mode analysis is carried out to design a defected ground structure that improves the MIMO performance without impacting negatively the radiation characteristics of the four-element array. Simulations and measurements demonstrate that the implemented prototype reaches a maximum mutual coupling of -32 dB and a gain-per-element of 5.3 dB with good MIMO attributes, surpassing many other proposals in the antenna literature: maximum envelope correlation coefficient of 0.0001, diversity gain very close to 10 dB, capacity loss (C loss ) near to 0.0023 bps/Hz at the resonant frequency, multiplexing efficiency (η muxij ) of 0.935, and a total active reflection coefficient weakly dependent on the excitation phases. The presented design is proposed for operation on the IEEE 802.11a/n standard.

Optimal Design of Compact Dual-Band Slot Antenna Using Particle Swarm Optimization for WLAN and WiMAX Applications

Background: A novel, small size, dual-band rectangular patch antenna with two narrow vertical slots for Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) application is presented here. Methods: The proposed antenna, fed by coaxial line, has dimensions of 21.075 mm ×17 mm ×1. 6 mm. With a pair of vertical slots, the antenna is resonating in 3.5 GHz WiMAX and 5.3 GHz WLAN band. The dimensions of the ground plane, substrate, radiating patch and two slots on the patch antenna are optimized using Particle Swarm Optimization (PSO) to obtain the desired operating frequency band. Results: The proposed antenna shows good radiation characteristics at these two operating bands, making it suitable for dual-band operation. Conclusion: The same design with some different physical parameter may be suitable for other kinds of wireless services. Further, application of Defected Ground Structure (DGS) to such models may also provide better performance.

Miniature Dual-Band Meander-Line Monopole Chip Antenna With Independent Band Control

A dual-band monopole chip antenna with an overall size of 5 × 3 × 2.1 mm3 is investigated for 2.4/5.2/5.8 GHz WLAN applications. The chip antenna has three substrates with four copper layers in total. It deploys a modified nonuniform folded meander line and capacitive loading patches to reduce the antenna size. A fundamental monopole mode and a higher order mode are excited to obtain the 2.4 GHz (2.40–2.48 GHz) and 5 GHz (5.150–5.350 GHz and 5.725–5.875 GHz) WLAN bands, respectively. The lower and upper bands can be independently controlled by the widths of the meander lines on the first and third layers, respectively. A prototype was fabricated and measured to verify the idea. A reasonable agreement between the measured and simulated results is observed. The measured 10 dB impedance bandwidths of the lower and upper bands are 5.3% (2.38–2.51 GHz) and 19.3% (5.14–6.24 GHz), respectively, fully covering the 2.4/5.2/5.8 GHz WLAN bands. The measured efficiency of the chip antenna is higher than 60% for the two bands.

A compact planar antenna with extended patch and truncated ground plane for ultra wide band application

AbstractIn this article, a compact broadband planar monopole microstrip patch antenna with extended patch and a truncated ground plane is proposed for ultra‐wideband application. The optimal dimensions of the proposed antenna are 20 × 20 × 1.6 mm3. The proposed antenna is fabricated on FR4 substrate that is a low‐cost commercially available substrate with εr = 4.3 and a loss tangent of 0.025. The impedance bandwidth (defined by the magnitude of S11 less than −10 dB) of the proposed antenna is 127% (3.13‐14.07 GHz). The peak gain and radiation efficiency of the proposed antenna are 3.4 dB and 78%, respectively. The proposed antenna exhibits a stable radiation pattern at the operating band. The simulated results of the proposed antenna are observed to be in agreement with the measured results when fabricated. The proposed antenna supports various frequency bands such as ultra‐wideband, 3.5/5.5 GHz WiMAX bands, 5.2/5.8 GHz WLAN bands, X Band (8‐12 GHz), satellite communication, and other wireless communication services. The proposed design and its various results have been discussed in further detail.

Compact, High Directivity, Omnidirectional Circularly Polarized Antenna Array

A compact omnidirectional circularly polarized (OCP) antenna system is reported, which achieves high directivity and operates with the 2.4 GHz WLAN band. It is formed by cascading several stages of electric (metallic strips) and magnetic (loops) radiators into a highly compact array. Two OCP antenna array designs are developed to demonstrate the approach and their resulting high directivities. First, a four-stage OCP antenna array is presented. It consists of three electric radiators (E-radiators) and four magnetic radiators (M-radiators) arranged in collinear formation. A prototype was realized by mechanically fabricating the folded copper loops. Measurements confirm that this compact cost-effective design generates OCP fields that have a 5.1 dBic peak LHCP realized gain in its horizontal plane. The overlapped impedance and AR bandwidth cover 130 MHz from 2.34 to 2.47 GHz. Second, a six-stage OCP antenna array with helical loops is implemented to further increase the directivity. Its prototype was realized with all-metal 3-D printing technology. Six stages of bar and helical loop radiators form five E-radiators and six M-radiators. This highly compact OCP array achieves a measured maximum realized gain of 7.1 dBic with a 110 MHz operational bandwidth that covers 2.37-2.48 GHz.

“Circularly polarized 4 × 4 MIMO antenna for WLAN applications”

ABSTRACTA circularly polarized (CP) 4 × 4 MIMO antenna with low mutual coupling is proposed to operate at 2.4 GHz WLAN band (IEEE 802.11b/g/n/ax) applications. The proposed design consists of four CP pentagonal microstrip elements with suspended substrate and five loaded slits to obtain the high gain and required impedance bandwidth. The CP elements are orthogonally arranged with diagonal element has same CP to reduce mutual coupling among the elements. The proposed MIMO antenna exhibits impedance bandwidth 170 MHz, a peak gain 7.95 dBd, and axial ratio ≤3 dB. More than 30 dB isolation is achieved between two elements. The MIMO antenna performance in terms of diversity gain (DG), efficiency, and envelope correlation coefficient (ECC) has been reported.

Dual circularly polarised omnidirectional antenna

A dual circularly polarised (CP) omnidirectional antenna is proposed. The antenna consists of an in-phase current loop, a printed dipole and a feed network. The in-phase current loop formed by zero-phase-shift line is placed orthogonally to the printed dipole to produce E φ and E θ components in the far-field of antenna radiation. By adjusting the amplitude and phase of E θ and E φ , good CP characteristics can be formed. A simple and feasible 3 dB coupler can realise the switching between the left-hand CP (LHCP) and right-hand CP (RHCP) without additional complex feed structure. Furthermore, the structure of the parallel strip line to the microstrip can effectively eliminate the unbalanced current of the coaxial cable. Finally, the optimised antenna was processed and measured. The measured results show that the impedance bandwidth (| S 11 |<;-10 dB) is 260 MHz (2320-2570 MHz) and 255 MHz (2340-2595 MHz) at two feed ports, respectively. It is worth mentioning that the antenna has a simple structure and a good omnidirectional CP radiation mode in the 2.45 GHz WLAN band.

Monostatic Copolarized Simultaneous Transmit and Receive (STAR) Antenna by Integrated Single-Layer Design

In this letter, a monostatic and cochannel simultaneous transmit and receive (STAR) antenna with identical circularly polarized radiations of transmitting (TX) and receiving (RX) channels is designed using a thin single-layer substrate. Four concentrically arranged microstrip radiating elements are properly excited by two sets of feeding networks: the feeding network of transmitting antenna (FNT) and the feeding network of receiving antenna (FNR). To fit FNT and FNR into the same plane, the FNR consists of a compact sequential-phase structure placed at the center of the antenna, while the FNT is aligned along the side with a planar crossover junction armed. Two vital techniques, orthogonal feeding points and leakage signal cancellation based on feeding networks, are utilized for satisfactory isolation level between the TX and RX ports. The experiment results demonstrate an isolation at least 41 dB and up to 54 dB, an axial ratio better than 1.7 dB, and a realized gain of 7.2 ∼ 10.5 dBic in the 2.4 GHz WLAN band. Our design scheme may overcome the profile and cost limitations of bulky multilayered STAR antennas, and thus portends potential for the highly integrated inband duplex systems.