WLAN Band Research Articles

Compact CPW-fed Antenna with Controllable WLAN Band-rejection for Microwave Imaging

This work presents the design and experimental validation of a compact frequency reconfigurable coplanar waveguide (CPW)-fed ultra-wideband (UWB) antenna with a capability to on-demand reject WLAN frequencies within the range of 5.15 GHz to 5.85 GHz, specifically tailored for applications in microwave imaging. The design and experimental results are presented and discussed. The bandwidth enhancement is obtained by using T-shaped slots between the feedline and the ground plane of the antenna, and the WLAN band is rejected by using an open loop resonator (OLR) placed on the antenna backside. Switching between UWB with and without WLAN band-notched modes is performed using a PIN diode and a bias circuit. The simulation results corroborate well with the experimental data and clearly showed an interesting frequency reconfigurable behavior for use in microwave imaging applications. An antenna performance simulation and analysis model is presented for breast tumor detection, and the tumor effect has been noticed for both operating modes of the antenna.

Multi-frequency composite wearable antenna for wireless communications

This paper proposes a multi-band composite wearable antenna for wireless communication, which uses a monopole structure as the radiating body and achieves multi-band characteristics through slit-loading and multi-branching methods. A polymer composite substrate with high dielectric constant and low dielectric loss was prepared using in situ polymerization, and the optimal dielectric constant and loss angle tangent were obtained by controlling the coating ratio of melamine formaldehyde resin to carbon nanotubes (MWCNTs) and the filler doping rate to achieve miniaturization of the antenna. Comparative experimental results show that the obtained composites have high flexibility and good dielectric properties. The antenna operates in the frequency bands of 2.21–2.52 GHz, 3.07–3.87 GHz, and 4.36–6.03 GHz, which cover the frequency bands of WLAN and WiMAX and 5G applications. The antenna was fabricated and tested, and its performance roughly matched the simulation results. Meanwhile, the antenna has passed the SAR safety test and maintained a stable performance under different curvatures, so it has potential applications in the wireless communication system.

A compact tri-notched flexible UWB antenna based on an inkjet-printable and plasma-activated silver nano ink

The rapid development of ultrawideband (UWB) communication systems has resulted in increasing performance requirements for the antenna system. In addition to a wide bandwidth, fast propagation rates and compact dimensions, flexibility, wearability or portability are also desirable for UWB antennas, as are excellent notch characteristics. Although progress has been made in the development of flexible/wearable antennas desired notch properties are still rather limited. Moreover, most presently available flexible UWB antennas are fabricated using environmentally not attractive subtractive etching-based processes. The usage of facile additive sustainably inkjet printing processes also utilizing low temperature plasma-activated conductive inks is rarely reported. In addition, the currently used tri-notched flexible UWB antenna designs have a relatively large footprint, which poses difficulties when integrated into miniaturized and compact communication devices. In this work, a silver nano ink is used to fabricate the antenna via inkjet printing and an efficient plasma sintering procedure. For the targeted UWB applications miniaturized tri-notched flexible antenna is realized on a flexible polyethylene terephthalate (PET) substrate with a compact size of 17.6 mm × 16 mm × 0.12 mm. The antenna operates in the UWB frequency band (2.9–10.61 GHz), and can shield interferences from WiMAX (3.3–3.6 GHz), WLAN (5.150–5.825 GHz) and X-uplink (7.9–8.4 GHz) bands, as well as exhibits a certain of bendability. Three nested "C" slots of different sizes were adopted to achieve notch features. The simulation and test results demonstrate that the proposed antenna can generate signal radiation in the desired UWB frequency band while retaining the desired notch properties and having acceptable SAR values on-body, making it a viable candidate for usage in flexible or wearable communication transmission devices. The research provides a facile and highly efficient method for fabricating flexible/wearable UWB antennas, that is, the effective combination of inkjet printing processing, flexible substrates, low temperature-activated conductive ink and antenna structure design.

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 28 nm CMOS Dual-Band Concurrent WLAN and Narrow Band Transmitter With On-Chip Feedforward TX-to-TX Interference Cancellation Path for Low Antenna-to-Antenna Isolation in IoT Devices

A 28 nm CMOS Dual-Band Concurrent WLAN and Narrow Band Transmitter With On-Chip Feedforward TX-to-TX Interference Cancellation Path for Low Antenna-to-Antenna Isolation in IoT Devices

A compound reconfigurable electronically switched parasitic monopole antenna for sub 6 GHz wireless and vehicular applications

In this paper, a compound reconfigurable electronically switched parasitic monopole antenna is reported for sub-6 GHz (n77/n78 bands) wireless standards and vehicular communication. The antenna comprises a half-hexagonal-shaped radiating element and two inverted L-shaped parasitic stubs. These stubs are connected through two PIN diodes, allowing for control over frequency. An additional pair of PIN diodes incorporates analogous parasitic stubs into the ground plane to facilitate pattern tilting and polarization. By switching these PIN diodes across seven operating states (OS), the antenna structure could resonate in a single band, spanning 4.5–5.8 GHz (sub-6 GHz higher band), with an omnidirectional pattern specific to OS1. In OS2 and OS3, the antenna resonates in a single band within the range of 4.1–5.7 GHz, featuring beam tilting with linear polarization. In OS4 and OS5, the structure has two bands: one covers 3.3–4.2 GHz (5G-n77 band) with linear polarization, and the other covers 5.1–6.1 GHz (5G WLAN band) with right-hand circular polarization (RHCP) in OS5 and left-hand circular polarization (LHCP) in OS4 with an axial ratio bandwidth of 14.5 %, including pattern tilting within the range of ± 340. Finally, in the OS6 and OS7 structure introduce dual bands of 3.3–3.8 GHz (5G–n78 band) and 4.8–5.8 GHz (sub-6 GHz higher band). Both bands feature LHCP/RHCP with an axial ratio bandwidth of 8.57 % for the lower resonant band and 7.4 % for the higher resonant band. Additionally, it incorporates radiation pattern reconfiguration capabilities. The structure is printed on an FR-4 substrate and measures various associated parameters. The experimental results closely match the simulated results.

Bandwidth Enhancement of a D-Crescent-Shaped Monopole Patch Antenna for Wireless Applications

A low-profile monopole patch antenna is proposed for wireless communication purposes, covering PCS1900, UMTS, LTE2300, LTE2500, ISM, and WLAN bands. The antenna features a novel double-crescent-shaped (D-Crescent-Shaped) patch with a partial ground plane to enhance bandwidth. Resonating at 2.4 GHz for ISM applications, the antenna, constructed on FR-4 dielectric, exhibits a proportional bandwidth of 38%, covering 1.91 GHz to 2.81 GHz. The design achieves a low-profile configuration with dimensions of 36.88×44.85 mm², featuring a thickness of 1.6 mm. The proposed antenna has a return loss of -56.1 dB and a directivity gain of 2.21 dBi. The proposed antenna, with its low-profile design, ease of manufacturing, and improved bandwidth and return loss, is well-suited for wireless communication applications across widely-used frequency ranges like PCS, UMTS, LTE2300, LTE2500, ISM, Wi-Fi, Bluetooth, and 4G LTE.

Improvement in notch band characteristics of a hexagonal super wideband antenna by interfering back radiation out of phase with front radiation using frequency selective surface

SummaryA band‐notched super wideband (SWB) planar monopole antenna with improved notch characteristics is proposed in this article. A hexagonal SWB antenna operating in the frequency range from 3.04 to 36 GHz is initially designed on Arlon substrate. The hexagonal patch is then loaded with optimum sized U‐shaped slot to eliminate WLAN band (5.15–5.85 GHz). The notch band's characteristics are further improved by incorporating a frequency selective surface (FSS) of a square array at a specific distance below the antenna to introduce a phase delay of 180° between the back radiation reflected by the FSS with the front radiation at the notched frequency. Improvement of notch band gain, efficiency, and antenna front‐to‐back ratio (FBR) are studied. The antenna without embedding an FSS exhibits working spectrum from 3.1 to 33.6 GHz with notch frequency gain of −2.6 dBi and efficiency 53%. The inclusion of an FSS layer at 25.2 mm behind the antenna results in notch frequency gain of −7.6 dBi with an efficiency of 23%. FBR improvement of about 16 dB is achieved at 8 GHz, and FBR is reduced by about 5 dB at the notch frequency. 169% fractional bandwidth with bandwidth dimension ratio (BDR) of 1622 is achieved in this proposed FSS integrated antenna. The inclusion of FSS to improve the band elimination performance represents the novelty of this proposal. The data are validated by electromagnetic simulation and physical measurement techniques.

An Ultra-Wideband Antenna with Triple Band-Notched Characteristics for Wearable Application

This work presents a compact UWB antenna with triple band-notched at WiMAX (3.2 GHz to 3.7 GHz), C-band (3.7 GHz to 4.2 GHz) and WLAN (5.15 GHz to 5.35 GHz) for wearable applications. The UWB antenna is fabricated on a semi-flexible thin FR-4 substrate. In order to reduce the complexity, only two slots are introduced on the radiating patch instead of three slots to reject each narrow band frequency. In this case, one slot rejects a combination of WiMAX and C-band and the other slot rejects the WLAN frequency band. The UWB antenna on the thin FR-4 material has an overall size of 21×16 mm2, which is very compact and thus, suitable for wearable applications without causing discomfort when worn on-body. Although the antenna is small in size, the performance is not compromised. The UWB antenna has the frequency range from 2.51 GHz to 12.09 GHz, maximum radiation efficiency of 100% and maximum gain of 4 dBi. Nevertheless, the antenna is able to reject the WiMAX and C-band as well as the WLAN band. The simulated specific absorption rate (SAR) results show that the antenna complies with the SAR limit Federal Communication Commission (FCC) and International Commission of Non-Ionizing Radiation Protections (ICNIRP) standards for 1 mW input power. Bending investigations performed on different diameters of Styrofoam cylinders shows that the frequency range and the notch bands are not very much affected.

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 Compact Self Isolated UWB-MIMO Antenna with WiMAX and WLAN Band Notched Characteristics for Portable Wireless Applications

A Compact Self Isolated UWB-MIMO Antenna with WiMAX and WLAN Band Notched Characteristics for Portable Wireless Applications

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).

Low-profile dual-band monopole antenna with EBG array for LTE, WLAN, Wi-MAX, and ISM band applications

Low-profile dual-band monopole antenna with EBG array for LTE, WLAN, Wi-MAX, and ISM band applications

Investigations on ACS-Fed Wearable Antenna With Frequency Reconfiguration Between n78 and WLAN Band

Investigations on ACS-Fed Wearable Antenna With Frequency Reconfiguration Between n78 and WLAN Band

Two new single/multi-objective multi-strategy algorithms for the parametric estimation of dual band-notched ultra wideband antennas

This article introduces a novel single objective and a multi-objective multi-hybrid naked mole-rat (moIGDN) algorithm optimization techniques for solving numerical benchmarks and electromagnetic engineering problems. The hybridization was introduced to overcome the basic naked mole-rat algorithm’s (NMRA’s) local optima stagnation and poor exploration problems. The global exploration search equations of INFO, gazelle optimization algorithm (GOA), and dwarf mongoose optimization algorithm (DMO) have been added into the NMRA’s worker phase. Additionally, five mutation operators have been introduced for parametric enhancements and adaptations. For single-objective performance evaluation, three benchmark datasets namely classical benchmark, CEC 2014, CEC 2017, and CEC 2022 have been analysed. A comparison with JADE, SaDE, CMA-ES, success history based DE (SHADE), fractional-order calculus-based FPA (FA-FPO), LSHADE-SPACMA, NL-SHADE-LBC, evolutionary algorithms with eigen crossover (EA4eig), S-LSHADE-DP, L-SHADE-RSP-MID, EBOwithCMAR, LSHADE-EpSin among others. Apart from that, the proposed moIGDN algorithm was utilized to optimize the design of two electromagnetic multi-objective printed monopole antennas categorized as basic ultra-wideband (B-UWB) and dual band-notched ultra-wideband (DBN-UWB) antennas. Simulations have been performed by using the EM-MATLAB optimization interface with two objective functions: trying to minimize pass-band signal reflection and maximizing antenna gain, by mapping solutions to the Pareto-front boundary in the objective space. The best obtained antenna structure had an impedance bandwidth of 2.92–11.96 GHz (fractional bandwidth of 122%), efficient band-rejection characteristics for the WI-MAX (3.3 GHz–3.7 GHz) and WLAN (5.15 GHz–5.85 GHz) bands, and a compact geometry. Based on simulation results, moIGDN is found to be effective and can be utilized to solve complex wireless communication and advanced engineering optimization problems.

Circular split ring resonator (SRR) slot and ground stub based slotted circular ultra-wideband MIMO antenna with WLAN band exclusion and high isolation performance

Circular split ring resonator (SRR) slot and ground stub based slotted circular ultra-wideband MIMO antenna with WLAN band exclusion and high isolation performance

A Highly Isolated Tapered Triangular Dual‐Polarized Multiband MIMO Antenna for WLAN, C, X and Ku Bands

This research work presents the design of a multiband dual‐polarized eight‐element MIMO antenna having dimensions (0.51 λ × 0.66 λ × 0.009 λ). The antenna is observed to be radiating between 1.7 GHz and 2.4 GHz, 4.1 GHz and 10 GHz and 10.6 GHz and 19.8 GHz, featuring 3 dB axial ratio bandwidth between 9.7 and 10 GHz, 12.1 and 13.1 GHz, 14.4 and 14.5 GHz and 17.9 and 18.9 GHz. In the proposed MIMO antenna, the triangular‐shaped monopole antenna is tapered at its two sides. The isolation between the various elements of the proposed antenna is observed to be in range of −20 dB–−70 dB for the concerned frequency range. On the basis of comparison with similar existing structures, the proposed antenna demonstrates superior performance in terms of total active reflection coefficient (TARC < −5 dB), diversity gain (DG around 10 dB), channel capacity loss (CCL < 0.3 bits/s/Hz), mean effective gain (MEG) and envelope correlation coefficient (ECC < 0.024). The proposed antenna provides wide bandwidth (15.8 GHz) and high value of peak gain (6 dB). The proposed geometry is novel as it exhibits both linear as well as circular polarization with multiband response and it provides the least ECC and maximum isolation. The experimental results are found to be in agreement with the simulated results, so the proposed antenna can be useful for WLAN, C‐band, X band and Ku band applications.

HEXAGON-SHAPED ANTENNA WITH DGS FOR BAND-NOTCHED ULTRA-WIDEBAND AND V2X APPLICATIONS

In this article, a compact and planar antenna is designed and investigated. The design is inspired by the hexagonal shape. The proposed design has a bandwidth of 11.22 GHz, from 3.16 GHz to 14.38 GHz. A suitably placed inverted-U slot in the patch generates a WLAN band notch. The overall size of the design is 20 × 26 mm<sup>2</sup> (0.21 × 0.27 λ<sub>0</sub><sup>2</sup> in terms of its highest wavelength). It is suitable to achieve a radiation pattern that is almost omnidirectional and has a maximum gain of 4 dBi in the passband. Simulated data is verified with the measured data and found to be in good agreement. The proposed design is suitable for sub-6 GHz, band-notched ultra-wideband, V2X, and modern wireless high-data-rate communication applications. KEY WORDS: defected ground, hexagonal shape, planar design, ultra-wideband, WLAN band notch

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.

Compact ACS-fed MIMO antenna with dual-band notch characteristics for UWB applications

Abstract An ultra-wideband (UWB) and compact-size four-port multiple input multiple output (MIMO) antenna with a footprint of 34 mm × 34 mm fed by an asymmetric coplanar strip (ACS) is investigated. The proposed antenna is composed of four orthogonally placed identical modified elliptical-shaped radiators and achieves an impedance bandwidth of 3.4–12.2 GHz. By etching two inverted L-shaped slots in the radiator element, WLAN band and X-band are rejected in the operating communication range. Because of the usage of a meander line decoupler, the isolation enhancement at the 8–12 GHz band is achieved and the isolation is more than 18 dB for most of the UWB range. The performance of the proposed antenna is studied in terms of isolation between each port, radiation pattern, current distribution, gain, envelope correlation coefficient, diversity gain, and total active reflection coefficient. The compact size and reduced complexity make the proposed design highly suitable for portable devices.