GHz Wireless Local Area Network Research Articles

FSS Design for Improving Transmission of Microwave Signals and Wireless Security in Modern Buildings

A fractal frequency selective surface (FSS) has been presented for hard coated energy saving glass (ESG) used in modern building architecture. Without FSS, the presence of coating on ESG surface blocks the transmission of useful radio frequency (RF)/microwave signals. The FSS consists of two self-similar cross dipole elements designed in the coating to provide a low-pass response from 0 GHz to 2.1 GHz with two additional band-stop responses at 2.45 GHz and 5.25 GHz. An average transmission loss of less than 2 dB has been achieved in the low-pass band while attenuations of 36 dB and 30 dB have been achieved for 2.45 GHz and 5.25 GHz wireless local area network (WLAN) bands, respectively, providing required security. The low-pass response improves the transmission of useful RF/microwave signals. However, the amount of removed coating due to FSS design is relatively higher, but heat loss has been minimized by pasting an inexpensive thin solar film on the back side of glass. This thin film has provided additional thermal insulation with almost no blockage to transmission of useful RF/microwave signals. A detailed parametric analysis has been done and their effect on FSS structure has been described. An equivalent circuit model has also been presented for the proposed FSS structure. A finite prototype containing 7 × 7 elements have been constructed and evaluated. The measured results have been found to be in good agreement with the simulated results. The proposed FSS design is an excellent candidate for WLAN security.

A Single-Layer Low-Profile Circularly Polarized Filtering Patch Antenna

A single-layer low-profile circularly polarized (CP) filtering patch antenna is investigated for wireless local area network (WLAN) applications. The CP antenna mainly consists of a feeding loop, four L-shaped radiating patches, and a square ground plane. To integrate the filtering function, four thin microstrip stubs and four shorting pins are introduced to the patches, and two U-shaped slots are etched in the feeding loop. These parasitic elements can realize the bandpass filtering function without requiring an external filter. In addition, these elements are skillfully added into the CP antenna, without increasing either the antenna footprint or profile. To verify the design, a prototype operating at 2.4 GHz WLAN band is fabricated and tested. The measured results show that the prototype has a low profile of 0.02λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , a passband bandwidth (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB and axial ratio (AR) <; 3 dB) of 4.1%, and a peak gain of 8.3 dBic. Moreover, the prototype also shows a sharp roll-off rate near the passband edge and a good out-of-band suppression level of more than 20 dB in the stopbands.

Compact Pattern Diversity Antenna with 3-D Printed All-dielectric Superstrate for WLAN Access Points

ABSTRACT This paper presents a four-port pattern diversity antenna with a 3-D printed all-dielectric superstrate for 5.2 GHz Wireless Local Area Network (WLAN) access points. The topology of four-port coaxial-fed circular patch antennas provides a beam tilt of ±45° and ±15° with an angular coverage of ±60°. The beam tilt is obtained through this unique topology, without the need for any additional phase shifting circuits. Then, a low-cost 3-D printed dielectric superstrate is designed to enhance and equalize the gain without compromising on the beam tilt and polarization purity of the antennas. The antenna module has an impedance bandwidth of 80 MHz (5.16 GHz–5.24 GHz), covering the IEEE 802.11ac band, for a gain of 9 dBi throughout the band and across the ports. The dielectric superstrate provides a gain enhancement of 3.8 dB for antennas 1 and 4, and 5.4 dB gain enhancement for antennas 2 and 3, respectively.

Design and analysis of 4 × 4 MIMO antenna with DGS for WLAN applications

AbstractIn this paper, a low profile 4 × 4 multiple input and multiple output (MIMO) antenna is proposed and designed for wireless local area network (WLAN) application using a square split-ring resonator. Initially, a single square-patch antenna is designed with square-shaped split-ring slot. Subsequently, the two-element MIMO antenna is designed and it is extended to four-element MIMO antenna. Finally, the defected ground structure (DGS) is implemented in order to enhance antenna performance. The antenna elements are placed opposite to each other. The mutual coupling between the antennas elements is reduced by DGS. The proposed single, two and four-element antennas operate at 5.8 GHz for WLAN. The overall performance is measured in terms of S parameter, radiation pattern, and envelope correlation coefficient. The simulated results are verified through measurements. The simulated and measured results demonstrate that the proposed 4 × 4 MIMO antenna is the most suitable for WLAN applications.

Tri‐band superconducting filter based on crossed resonators with controllable coupling and feeding structures

In this article, a compact tri-band high-temperature superconducting filter with controllable coupling and feeding structures based on crossed resonator which consists of two-end-open UIR with a short stub and an open stub shunted at the resonator center is proposed. Due to the symmetrical structure of the proposed resonator, the odd- and even-mode analysis method can be used to derive their resonance frequencies. Then, a capacitance-loaded microstrip line is added between the resonators to flexibly control the bandwidths. Furthermore, one tapped line and one coupled line are utilized to realize the acquired external coupling under prior specifications. For demonstration, a tri-band filter operating at 1.6 GHz (Global Positioning System), 2.45 GHz (Wireless Local Area Networks), and 3.5 GHz (WiMAX) is designed, analyzed using the electromagnetic simulator, and fabricated using an YBa2Cu3Oy thin film on an MgO substrate. The measured results agree well with the simulated ones.

Integrated Four Low-Profile Shorted Patch Dual-Band WLAN MIMO Antennas for Mobile Device Applications

Four dual-band shorted patch antennas (SPAs) with a low profile of 1 mm ( $0.008\lambda $ at 2.4 GHz) integrated into a square-ring structure of size 66 mm $\times66$ mm (about 0.53 $\lambda \times 0.53\lambda $ at 2.4 GHz) for 4 $\times {4}$ multiinput-multioutput (MIMO) operation are presented for mobile device applications. Each SPA consists of a larger shorted patch and a smaller shorted patch to, respectively, generate the 2.4 GHz band (2400–2484 MHz) and 5.8 GHz band (5725–5875 MHz) for dual-band wireless local area network (WLAN) operation. Two SPAs are orthogonally connected with the first SPA’s larger shorted patch and the second SPA’s smaller shorted patch sharing a common metal wall at the corner of the square-ring structure. By repetitively connecting the third SPA to the second one and finally the fourth SPA to the third and first ones, the proposed design can generate four decoupled waves in the 2.4 GHz/5.8 GHz WLAN bands with very low envelope correlation coefficients of less than 0.1. With 1 mm low profile, the proposed WLAN MIMO antennas are expected to find applications in integration with the back cover of the mobile device.

Circularly-polarized linear antenna array of non-identical radiating patch elements for WiFi/WLAN applications

Here we present a novel linear circularly polarized (CP) antenna array using non-identical CP elements, where the Chinese character-shaped patches are employed to form a linear array. Namely, the single-feed CP Zhong-, Guo-, and Meng-shaped patch antennas have collected to form a three-element antenna array. A one-to-three power splitter with equal amplitudes but unequal phase-shifts at its output ports was deliberated as the feed network for the linear array. The challenge of this antenna array design is the appropriate phase excitation to the non-identical radiating elements so that the CP gain and operating bandwidth can meet the requirements of the application(s), in which we undertook an in-depth investigation. A proof-of-concept design example for 2.4 GHz wireless local area network (WLAN, IEEE 802.11b/g/n) has demonstrated the effectiveness of the combination technique on the non-identical CP antenna elements. The simulation, in combination with experimental validation, obtained an on-axis 3-dB axial-ratio bandwidth from 2.28 to 2.59 GHz (12.7%), whereas a broadside gain of 9 dBic at 2.5 GHz and an overall efficiency of 82% were recorded within the bandwidth.

Compact ACS-fed monopole antenna with CRR defect for triple band application

A compact asymmetric coplanar strip fed monopole antenna for the triple-band operation is discussed. The introduction of the defected structure along with asymmetric coplanar strip feeding is an effective way of reducing the antenna size. The rectangular complimentary ring resonator is in the ground plane and another inverted T shaped slot at the radiating strip etched for achieving triple-band operation and interference suppression. The proposed antenna is 25 × 12 mm2 and has been fabricated and tested. The measured results reveal that the proposed antenna has impedance bandwidths of 340 MHz (2.36–2.70 MHz), 390 MHz (3.35–3.74 GHz) and 1110 MHz (5.01–6.12 GHz), which is required for 2.4/3.5/5.2 GHz wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications.

A miniaturized high gain dipole array antenna for 2.4/5 GHz wireless local area network applications

AbstractA miniaturized high gain dipole array antenna for 2.4/5 GHz wireless local area network (WLAN) applications (2.4‐2.5/5.15‐5.85 GHz) is proposed in this paper. The proposed antenna is composed of a 1 × 3 dipole array, a U‐shaped branch, and a double‐layer feedline. Dual‐band operation is realized by using a double‐branch dipole. The peak gain of the proposed dipole array antenna is improved due to the in‐phase current distributions on dipole elements. A U‐shaped branch is added to further enhance the peak gain in the lower band. For miniaturization, the half‐cutting method is applied. One prototype of the proposed miniaturized antenna with a size of 168 × 10.5 × 0.6 mm3 is manufactured and measured. As a result, the proposed antenna provides the operating bands of 2.30 to 2.59 GHz and 5.10 to 6.73 GHz (voltage standing wave ratio ≤ 2), fully covering 2.4/5 GHz WLAN band. Over the lower/higher band, the peak gain and efficiency are higher than 4.2/5 dBi and 58%/49%, respectively. Furthermore, good omnidirectional radiation characteristic in the horizontal plane is achieved.

Reconfigurable 2.4-/5-GHz Dual-Band Transmitter Front-End Supporting 1024-QAM for WLAN 802.11ax Application in 40-nm CMOS

This article presents a new design methodology of a reconfigurable dual-band output matching network with high efficiency. The implemented output matching network achieves a passive efficiency of 71.6% and 75% at 2.4 and 5.5 GHz, respectively. Based on the proposed output matching network, a transmitter and a standalone power amplifier (PA) supporting 2.4-/5-GHz dual-band operation for the emerging wireless local area network (WLAN) 802.11ax application are designed and fabricated in 40-nm CMOS technology. In 2.4- and 5-GHz WLAN bands, the PA achieves a P sat of 23 and 21.9-22.4 dBm with power-added efficiency (PAE) of 27% and 24.2%-28.2%, respectively. At 2.442 GHz, the transmitter delivers 8.1-dBm average output power for 40-MHz, 1024-quadrature amplitude modulation (QAM) 802.11ax signal while meeting the standard specification of error vector magnitude (EVM) below -35 dB. In 5-GHz operating mode, the transmitter achieves an average output power of 6.72-6.95 dBm with the EVM of -35 dB for 80-MHz, 1024-QAM 802.11ax signal. The PA and transmitter front end are the first published designs for dual-band WLAN 802.11ax application in the literature.

An ultra-thin, dual band, Sub 6 GHz, 5G and WLAN antenna for next generation laptop computers

PurposeThe purpose of this manuscript is to present a novel, compact and ultra-thin “3”-shaped monopole antenna for wireless operations in the laptop computer. The thickness of the antenna is only 0.2 mm and is designed using only a pure copper strip of size 17.5 × 6 mm2.Design/methodology/approachThe simple structure of the proposed antenna consists of two monopole radiating strips, namely, AC and CD and an open-ended rectangular tuning stub BE of length 9mm.FindingsThis structure inspires two resonating modes at 3.45 and 5.5 GHz and achieves the measured impedance band width as 20% (3.21-3.91) GHz in lower band (F_l) and 15% (5.05-5.85) GHz in the upper band (F_u) for voltage standing wave ratio < 2. These two bands cover 5GHz wireless local area network (WLAN) and 3.3-3.6GHz (sub 6GHz) 5G bands. The measured radiation performance including, nearly omnidirectional radiation patterns, a stable gain of around 5 dBi and excellent efficiency around 90% in both operating bands have been achieved. Furthermore, a simplified equivalent circuit model has been derived and its simulation is performed. The simulated and measured results are in good agreement, which demonstrates the applicability of the antenna structure for WiMAX/WLAN operations in the prominent ultra-thin laptop computers.Originality/valueThe proposed antenna is designed without using any reactive elements, vias or matching circuits for excitation of WLAN and 5G bands in the laptop computers. The design also does not require any additional ground for mounting the antenna. The proposed antenna has a very low profile, is ultra-thin, cost-effective, easy to manufacture and can be easily embedded inside next generation laptop computers.

Salt and sugar detection system using a compact microstrip patch antenna

Abstract One of the reasons for many diseases such as diabetes, stroke, high blood pressure, kidney disease, etc., is the excess consumption of salt and sugar in the diet. So, to minimize these health problems, it is important to consume appropriate quantity of salt and sugar in the diet. This paper presents the design and development of a salt and sugar detection system using a low cost compact microstrip patch antenna. The salt and sugar detection system using a compact microstrip antenna is based upon the variation of antenna parameters in the solutions of different concentrations of salt and sugar. The defected ground structure (DGS) is utilized for decreasing the size and improving the performance of the proposed microstrip patch antenna. The antenna is fed by using a microstrip line and it resonates at 2.4 GHz. The designed antenna is simulated and optimized using the computer simulation technology (CST) microwave studio. The antenna with optimized dimensions is fabricated and measured. The measurements of the return loss of the fabricated microstrip patch antenna for various solutions with different concentrations of salt and sugar are performed. The measured results confirm that the proposed compact microstrip patch antenna is suitable to detect the concentration of salt and sugar in the water. From the measured results, it is observed that the return loss of the antenna decreases, when the concentration of salt and sugar is increased. The proposed antenna is also suitable for compact 2.4 GHz wireless local area networks (WLAN) applications.

Design of Smartwatch Integrated Antenna With Polarization Diversity

A design of smartwatch integrated antenna with polarization diversity is proposed. An annular ring is integrated in the framework of smartwatch, and excited by two ports. One port is fed by a coplanar waveguide (CPW) line loaded with a T-shaped matching network, and the other is fed by a coplanar strip line (CPS). The overall model of the proposed antenna has a cylindrical shape with 38 mm diameter and 7.5 mm thickness. A metallic plate is located at the backside of the antenna to mimic the shell of smartwatch. The prototype is fabricated and measured, and the measured results agree well with the numerical ones. The two ports have orthometric radiation patterns and can cover the 2.4 GHz wireless local area network (WLAN) band. The gain of the antenna is higher than 3.2 dBi in free space. The proposed antenna is also analyzed with a cubic tissue model and a wrist model in different distances between the proposed antenna and human models. The performances on body scenarios are also acceptable. The values of specific absorption rate (SAR) in the cubic tissue model and wrist model are below the limitations set by both the Federal Communication Commission (FCC) and the European Telecommunication Standards Institute (ETSI). Envelope correlation coefficient (ECC) shows proposed antenna can be used in multiple input multiple output (MIMO) applications. The influence of battery and printed circuits board assembly (PCBA) on S parameters is obvious, and gain and radiation efficiency are not much affected.

Dual-Band Dual-Polarized Wearable Button Array With Miniaturized Radiator.

A dual-band dual-polarized wearable array is proposed, based on a miniaturized innovating button radiator topology. The diameter of the rigid button is only 19.5 mm (0.29 λ at 4.5GHz), which optimizes the users' comfort, and makes it the smallest up to date in literature. The operational bands are 4.50-4.61GHz and 5.04-5.50GHz. The antenna thus covers the 4.5-4.6 unlicensed future 5th generation (5G) communication band for the internet of things (IoT), and the 5.1-5.5GHz wireless local area network (WLAN) band, respectively. Two orthogonal linear polarizations are obtained in each band. A low mutual coupling between the button antenna elements (below -18dB) and between the two ports within each element (below -20dB) is achieved, guaranteeing a good diversity performance. The envelope correlation coefficient (ECC) and the specific absorption rate (SAR) performance are also analyzed. In order to demonstrate the robustness of the button antenna and to mimic realistic situations, a more complicated asymmetrical ground plane model of the button antenna is studied for the first time. A prototype of a two-element button array has been fabricated. The measurement results match well with the simulations. A 10-element button array is studied within the context of a 3-D channel model, taking into account the button element's radiation pattern. A high achievable spectral efficiency (SE) is obtained.

A novel UWB MIMO antenna array with band notch characteristics using parasitic decoupler

ABSTRACT This paper presents a 4 × 4 multiple-input–multiple-output (MIMO) antenna array for ultra-wide band (UWB) applications with 5.5 GHz wireless local area network (WLAN) band rejection characteristics. The single UWB antenna element consists of modified patch antenna with partial ground plane. WLAN band has been rejected by etching a U-shaped slot in the antenna element. The antenna elements have been arranged in a planar geometry where each element is orthogonal to its adjacent element. A fan-shaped parasitic decoupler, that consists of four strip lines connected with a central square-shaped conductor, is placed among the antenna elements. The dimensions of the antenna array are 67 × 67 × 1.6 mm3. Full wave simulations and experiments have been conducted where measured peak gain and average isolation were 8.1 and −20 dB, respectively. The calculated envelop correction coefficient was less than 0.01.

A Planar Integrated UWB/Reconfigurable Antenna with Continuous and Wide Frequency Tuning Range for Interweave Cognitive Radio Applications

This paper presents a planar ultra-wide band (UWB) sensing antenna accompanied with a monopole narrow band communicating antenna for interweave cognitive radio (CR) applications. The UWB antenna bandwidth covers the entire band specified for UWB applications (3.1–10.6 GHz). In addition to the varactor diode, a PIN diode is attached to the communicating antenna to expand the continuous frequency tuning of the varactor diode up to 3 GHz along the frequency range (3.3–6.3 GHz) including WiMAX, personal area network, and the 5 GHz wireless local area network. The UWB sensing antenna shape and the ground plane size of the communicating antenna are modified to reduce the mutual coupling between the two antennas to values less than − 15 dB. The measurements are well agreed with the simulation, and they verify the antenna suitability for CR systems. Moreover, the results show an omnidirectional power pattern for both sensing and communicating antennas which is compatible to the portable CR devices.

Design and Analysis of an Ultraminiaturized Frequency Selective Surface With Two Arbitrary Stopbands

The paper proposes a new design and its analysis of a 2.5-D ultraminiaturized frequency selective surface (FSS) with two arbitrarily and independently adjustable stopbands. These two stopbands can be adjusted very far away or combined to a single wideband. This new FSS consists of only one dielectric layer printed on both sides with refined meandering-lines connecting vertical via arrays. By applying the proposed approach with an exactly equivalent circuit and closed-form equations, four representative prototypes are demonstrated. The first one has two distant stopbands, which high-to-low resonant frequency ratio can be as large as 6.2. The second one shows that its unit-cell size can be highly reduced to only 2.8% of the free space wavelength at the lower resonant frequency. The third one has a wide stopband, having a fractional bandwidth up to 75.7%. The final one meets the specification of 2.4-GHz and 5-GHz wireless local area network application. The simulated and measured results both validate the FSS performance and demonstrate its excellent versatility never found in literatures before.

Association, Blockage, and Handoffs in IEEE 802.11ad-Based 60-GHz Picocells—A Closer Look

The link misalignment and high susceptibility to blockages are the biggest hurdles in realizing 60GHz based wireless local area networks (WLANs). However, much of the previous studies investigating 60GHz alignment and blockage issues do not provide an accurate quantitative evaluation from the perspective of WLANs. In this paper, we present an in-depth quantitative evaluation of commodity IEEE 802.11ad devices by forming a 60GHz WLAN with two docking stations mimicking as access points (APs). Through extensive experiments, we provide important insights about directional coverage pattern of antennas, communication range and co-channel interference and blockages. We are able to measure the IEEE 802.11ad link alignment and association overheads in absolute time units. With a very high accuracy (96-97%), our blockage characterization can differentiate between temporary and permanent blockages caused by humans in the indoor environment, which is a key insight. Utilizing our blockage characterization, we also demonstrate intelligent handoff to alternate APs using consumergrade IEEE 802.11ad devices. Our blockage-induced handoff experiments provide important insights that would be helpful in integrating millimeter wave based WLANs into future wireless networks.

Compact Two-Inverted-F-Antenna System With Highly Integrated $\pi$ -Shaped Decoupling Structure

Conventional decoupling technique uses the resonator-based grounded structure that separates two antennas at a distance for improving port-to-port isolation. The decoupling structure usually requires certain space, which increases the overall antenna size. In this communication, a small $\pi $ -shaped structure that can be highly integrated into a very compact two-inverted-F-antenna (IFA) system is presented. The two-IFA design occupies a size of 5 mm $\times38$ mm (about $0.04\lambda \times 0.30\lambda $ at 2.4 GHz) with two symmetrical IFAs facing each other by a gap of 2 mm only. Each IFA is capable of covering the 2.4 GHz (2400–2484 MHz) and 5 GHz (5150–5825 MHz) wireless local area network (WLAN) bands. The $\pi $ -shaped decoupling structure is encircled by the IFAs and comprises two shunt capacitors and a series inductor. By properly selecting the capacitance and the inductance, the isolation between the IFAs in 2.4 GHz band can be largely enhanced. In addition, because of current null arrangements of the 5 GHz band, the proposed design is inherently decoupled over the higher band. The results show that good isolation >16 dB over the 2.4 and 5 GHz bands can be attained. It is also noted that the decoupling bandwidth of the present decoupling structure is narrow.

Received Signal Strength Indication (RSSI) of 2.4 GHz and 5 GHz Wireless Local Area Network Systems Projected over Land and Sea for Near-Shore Maritime Robot Operations

The effect of the maritime environment on radio frequency (RF) propagation is not well understood. In this work, we study the propagation of ad hoc 2.4 GHz and 5 GHz wireless local area network systems typically used for near-shore operation of unmanned surface vehicles. In previous work, maritime RF propagation performance is evaluated by collecting RSSI data over water and comparing it against existing propagation models. However, the multivariate effect of the maritime environment on RF propagation means that these single-domain studies cannot distinguish between factors unique to the maritime environment and factors that exist in typical terrestrial RF systems. In this work, we isolate the effect of the maritime environment by collecting RSSI data over land and over seawater at two different frequencies and two different ground station antenna heights with the same physical system in essentially the same location. Results show that our 2.4 GHz, 2 m antenna height system received a 2 to 3 dBm path loss when transitioning from over-land to over-seawater (equivalent to a 25 to 40% reduction in range); but increasing the frequency and antenna height to 5 GHz, 5 m respectively resulted in no meaningful path loss under the same conditions; this reduction in path loss by varying frequency and antenna height has not been demonstrated in previous work. In addition, we studied the change in ground reflectivity coefficient, R , when transitioning from over-land to over-seawater. Results show that R remained relatively constant, −0.49 ≤ R ≤ −0.45, for all of the over-land experiments; however, R demonstrated a frequency dependence during the over-seawater experiments, ranging from −0.39 ≤ R ≤ −0.33 at 2.4 GHz, and −0.51 ≤ R ≤ −0.50 at 5 GHz.