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A novel compact rectangular fractal-shaped antenna for tri-band wireless communication applications is developed in this article. The proposed fractal shaped is achieved by cutting two rectangular slots in the rectangular monopole. Additionally, a stub is introduced in the bottom side of the antenna to enhance the impedance bandwidth of the acquired three bands. The developed antenna has a compact size 22 × 34 × 1.6 mm3. The CST MWS is used to design the antenna and its characteristics including S11, current distribution, radiation characteristics are exposed and analysed. To demonstrate that the simulation outcomes are reliable, the suggested antenna is manufactured and put through testing on an E5071C VNA. Additionally, the results of the experiments demonstrate that the designed antenna offers three impedance bandwidths 2.25–2.96 GHz, 3.56–4.01 GHz, and 4.6–5.86 GHz, which shields all the LTE, WLAN, WiMAX, and C-band applications. The proposed tri-band fractal antenna also provides good gain at the operating frequencies and an omnidirectional radiation pattern. [ABSTRACT FROM AUTHOR]

In this paper, a CPW-fed compact antenna with tri-band reject characteristics is presented and experimentally verified. A curved ground plane is introduced to enhance the bandwidth to 250 MHz. The sectoral patch antenna has a T-strip and Y-slot to reject WLAN (4.78 ∼ 5.68 GHz) and WiMAX (3.385 ∼ 3.97 GHz), respectively. L-strips are placed in the ground plane to increase the bandwidth as well as the plane to reject uplink satellite frequency in the X-band (7.93 ∼ 8.74 GHz). In all notch bands, high VSWR values are observed. The structure is compact with a size of 15 × 12 × 0.8 mm3. To study the effect of strip/slot on VSWR, parametric analysis is done. The notch frequency is theoretically calculated by an empirical formula. The measured result validates the simulated and calculated notch frequencies. [ABSTRACT FROM AUTHOR]

In this article, an F-shaped four-port multiple-input multiple-output (MIMO) antenna is designed and analyzed. In the designed antenna for achieving high isolation, we introduced a novel isolation technique that appears like plus-shaped wall placed in between the antenna elements. The antenna is designed on a low-cost FR-4 epoxy substrate with total dimensions of 0.61 $ \lambda _{0}\times 0.61\lambda _{0}\times 0.03\lambda _{0} $ λ 0 × 0.61 λ 0 × 0.03 λ 0 (31 mm × 31 mm × 1.58 mm) where $ \lambda _{0} $ λ 0 is the free space wavelength at 5.8 GHz and experimentally verified. This MIMO antenna design covers operating the range of frequencies 5.47–6.20 GHz ( $ |S_{11}| \lt - $ | S 11 | < − 10 dB) which provides a bandwidth of 730 MHz. In terms of performance, the proposed antenna achieves high isolation of $ \lt -45.52 $ < − 45.52 dB with an improved reflection coefficient of $ -30.44 $ − 30.44 dB, a peak gain of 3.77 dBi and a radiation efficiency more than 82% across the entire operating band. Moreover, the achieved MIMO diversity parameters of the proposed antenna are envelope correlation coefficient < 0.005, diversity gain $ \lt 9.99 $ < 9.99 dB, mean effective gain $ \lt -3 $ < − 3 dB and total active reflection coefficient $ \lt -10 $ < − 10 dB in the operating band of frequency. The simulated and measured results show a good agreement between them. Finally, after analyzing the performance of the proposed MIMO configuration, we can say that this antenna is suitable for C-band, WiMAX, Wireless-Fidelity (Wi-Fi), Wireless Local-Area Network (WLAN), Bluetooth and Industrial, Scientific, & Medical (ISM) bands applications. [ABSTRACT FROM AUTHOR]

This paper reports multiband microwave access multiple-input-multiple-output (MIMO) four-port antenna for UWB-X (3.10–12.0 GHz) band applications radiating electromagnetic energy with dual notched bands and compact size of 0.68λo × 0.92λo. Two notched bands are introduced on the radiating patch of the antenna and microstrip feed line mitigating Wireless-Local-Area-Network (WLAN: 5.11–5.88 GHz) & Downlink-Uplink Satellite (DUS: 7.28–8.36 GHz) interference. The technology reported includes simulated results and is validated by comparing the measured results of the 4 × 4 MIMO antenna. The mutual coupling between the radiating patch is suppressed below −15.0 dB which is achieved by interconnecting the ground and placing a cross-shaped parasitic patch between the radiating elements. The proposed MIMO antenna offers maximum gain efficiency of 5.92dBi & 0.95 (95%), respectively. The diversity parameters (ECCmax = 6 × 10−4, DGmax = 9.99 dB, TARCmax = −27.0 dB, CCLmax = 0.015b/s/Hz, MEG $ \approx $ ≈ −3.0 dB) are in the permissible range given by International Telecommunication Union (ITU) for information and communication technology. [ABSTRACT FROM AUTHOR]

A low-cost three-port series-fed antenna array with pattern diversity for WLAN applications is presented. The three antennas resonate at 5.8 GHz with 12 dBi antenna gain. The antenna substrate consists of an air cavity within the substrate, which is introduced to enhance the gain and radiation efficiency. The principle of micromachining was used to realize the substrate characteristic that lowers the dielectric constant, compared to a conventional non-micromachined substrate. The antenna uses scaled parasitic patches as a superstrate to improve and equalize the gain of the respective antennas when the antenna beam scans through +180, 00, and −180. The parasitic patches as a superstrate were found to have low scanning loss when the antenna beam is tilted from the broadside. The proposed superstrate design enhances the gain at the broadside and oblique radiations making the design more versatile as the gain enhancement becomes invariant to the incidence angle. The planar superstrate enhances the gains of three antennas with 2.4, 2.8, and 7.1 dB so that the final antenna gain is equalized to 12 dBi at the three ports. To validate the design, the antenna module is fabricated on the polylactic acid (PLA) substrate using the industry-standard photolithography process. [ABSTRACT FROM AUTHOR]

This paper presents a source degenerated cascode low noise amplifier (LNA) design using a regulated cascode active inductor (AI). The AI has an inductance value of up to 6.28 nH, a Q-value of up to 4750, and a resonant frequency of up to 9.758 GHz. The proposed AI replaces the passive source degenerated inductor and load inductor in the LNA. Further, an active balun is used to have a differential signal at the LNA output to support the mixer stage. The gain and noise figure of the LNA is 22.2 and 5.6 dB respectively. The 3rd order input intercept (IIP3) value is 1.92 dBm and the return losses at the input port and two output ports are less than −10 dB. The power consumption of the circuit is 27 mW at a 1.8 V supply and the figure of merit (FoM) is 9.17. The area occupied by the AI is 39 × 72 µm2 and balun-LNA is 0.872 × 0.62 mm2. The complete proposed circuit is meant for wireless local area network (WLAN) applications in the 2.4 GHz frequency band. [ABSTRACT FROM AUTHOR]

In this work, we integrated narrow band (NB) and Ultra-Wide Band (UWB) four-port MIMO antennas designed and implemented in IoT applications. The designed antenna consists of two quarter-wavelength asymmetrical NB radiators and a reverse P-shaped UWB radiator. The two NBs are generated by two quarter-wavelength non-identical radiators, and the UWB is generated by a semi-circle-shaped monopole radiator. Further, the NB radiators and UWB radiators are connected in a 3-mm-wide feed line. The antenna is designed to operate at 1.8 GHz (3G), 2.4 GHz (WLAN), and 3.1–12 GHz (UWB) for IoT applications. In this designed four-port MIMO antenna, two proposed NB and UWB radiators are mounted on the front side of the FR4 substrate and the other two on the rear side of the FR4 substrate. The proposed MIMO antenna has a dimension of $ 65 \times 65 \times 1.6\,{\rm mm}^3 $ 65 × 65 × 1.6 mm 3 . The antenna performance and MIMO performance are analyzed. The diversity metrics such as ECC, DG, TARC, MEG, and CCL are computed, and their values are 0.26, 9.87 dB, −22 dB, −6 dB, and 0.27 bits/Hz/s, respectively, within the bounds. The real-time implementation of the designed antenna is demonstrated at 2.4 GHz for smart home applications. [ABSTRACT FROM AUTHOR]

A single-substrate-layer Frequency Selective Surface (FSS) is designed with a 1.6 mm thick FR4 substrate for triple band-stop frequency filtering applications, that are for Bluetooth, WLAN, WiMAX, and X-band. The proposed FSS unit cell consists of two polygon loops on the front side and a square loop with four annular rings attached to its corners on the backside. The offered design covers three frequency bands: 2.3-4 GHz, 5-6 GHz, and 8-12 GHz. There are three resonances at 3.3, 5.6, and 9.9 GHz. The equivalent circuit model of the proposed structure and the formulas of the LC parameters are presented. A prototype of this structure was manufactured in size of 26 × 26 cm2 and experimentally verified in the antenna and microwave laboratory. The software used for design and simulation is HFSS from Ansys, which uses the finite element method. A comparison with similar structures was performed to demonstrate the performance of the proposed structure. The advantages of the proposed filter include adequate bandwidth, simple structure, as well as small size. In addition, it is unaffected by variant angles of incidence for TE polarization and TM polarization. Furthermore, due to its symmetrical design, it shows a polarization-independent feature. Experimental results for both polarizations verify the merits of the proposed approach, as shown before in the simulation results as well. [ABSTRACT FROM AUTHOR]

This article describes a quad-port ultra-wideband multiple-input multiple-output (MIMO) antenna with dual-band notch characteristics that is very compact and highly isolated. The compactness and high isolation of this design are achieved by etching a modified Minkowski fractal structure and an inverted L-shaped stub made available by the partial ground plane. Simply by incorporating 'C'- and 'U'-shaped slots in the radiating patch, it is possible to obtain dual-band rejection characteristics that are very suitable for wireless local area network band and X-band downlink satellite communication of 5.0–5.9 GHz and 7.1–7.9 GHz, respectively, in this proposed structure. The entire design is housed in a very compact size of 30 mm × 30 mm. A few key parameters, such as channel capacity loss (CCL), envelope correlation coefficient (ECC), diversity gain (DG) and total active reflection coefficient (TARC), are examined to ensure that the MIMO system meets its requirements. Furthermore, a mutual coupling value of less than −22 dB and an operating frequency band of 3.1–12 GHz allow the design to be very effective in a multipath channel environment. [ABSTRACT FROM AUTHOR]

In this paper, on-demand rejection of interfering bands with operating band intended for UWB-X band applications utilizing a diversity antenna with a dimension of 24 × 48 mm2 has been reported. Two sharp rejecting bands, WiMAX and WLAN are obtained by using an anchor-shaped stub embedded within a slotted radiating patch and externally connected C-type stub. MIMO antenna configuration offers isolation of more the 30 db in both measured and simulation environments. The designed MIMO antenna offers good time-domain characteristics and is characterized utilizing various parameters including S-parameters, radiation efficiency, far-field gain, radiation pattern, ECC, DG, TARC, and CCL. [ABSTRACT FROM AUTHOR]

This paper introduces a design methodology that reduces the fundamental trade-off between linearity and power added efficiency (PAE) in CMOS power amplifier (PA). In our work, a stacked power block (SPB) has been proposed to mitigate the effect of gate–source capacitance (Cgs), thus linearizing the PA. Each stage is biased independently to shape the gain profile, either to be in the expanded mode or in the compressed mode, in which once combined it delivers a flat gain response and confirming the linearity performance. Efficient PI input and output matching networks are proposed to ensure no further distortion, once connected to the 50 Ω source and load. The PA achieves input and output return losses of less than −10 dB from 2.40 to 2.50 GHz. At the center frequency of 2.45 GHz, the SPB-PA achieves a gain of 10 dB and it is unconditionally stable. The proposed gain shaping linearization technique delivers a maximum linear output power (Poutlinmax) of 19.8 dBm with only 3.3 dB back-off from maximum output power (Poutmax) of 23.1 dBm. The SPB-PA meets the WLAN specification with linear PAE of 30% and peak PAE of 36.1%. The proposed SPB-PA reduces the fundamental trade-off between linearity and efficiency. Integration of this PA in wireless SoC shall reduce the chip's overall power consumption. [ABSTRACT FROM AUTHOR]

The proposed antenna presents a dual-band monopole antenna with a wide axial ratio bandwidth, by using the modified ground plane. The tilted inverted L-shaped strip with an angle of α is printed on the FR4-epoxy substrate and is excited by the microstrip feedline. The overall dimension of the proposed antenna is 0.408λ0 × 0.326λ0 × 0.013λ0. The ground plane has been modified by introducing a Y-shaped strip, cutting a slot and connecting a stub for improving the characteristics of antenna performance. The design and simulation have been carried out by the EM simulator HFSS v.15 software. Once the antenna design is completed, the proposed antenna is fabricated and various characteristics are measured. The proposed antenna exhibits two distinct bands along with the percentage impedance bandwidths and axial ratio bandwidths of 75.32% (resonant at 2.35 GHz), 14.26% (resonant at 6.1 GHz) and 55.88% (center at 2.845 GHz), 15.96% (center at 6.075 GHz), respectively. The measured results are experimentally verified with simulated results and a good agreement is found between them. The measured impedance bandwidth, axial ratio and gain are good enough for commercial bands of wireless communication systems such as Bluetooth, Wi-Fi, WLAN, and WiMAX. [ABSTRACT FROM AUTHOR]

A two-element MIMO antenna, with improved isolation and pattern diversity, is designed and presented. The dual-band MIMO covers both the adjacent upper WLAN (5.2 GHz) and WiMAX (5.8 GHz) bands with clear isolation between them. The unit radiator of the MIMO is a co-planar waveguide-fed trapezoidal patch that achieves its resonant modes by adjusting the slope of the non-parallel sides. A frequency selective meta-structure is placed in-between the two radiating elements to reduce the mutual coupling and achieve pattern diversity. The MIMO offers peak gains of 1.56 and 5.16 dB at 5.2 GHz (5.1–5.34 GHz) and 5.8 GHz (5.68–5.9 GHz), respectively. The port-isolations achieved at WLAN and WiMAX bands are 26 and 23 dB, respectively. The correlation co-efficient (ECC < 0.05), diversity gain (DG > 9.99) and channel capacity loss (CCL < 0.03) also adhere to the criteria for MIMO operation. The measured results are in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

A four-element multiple-input-multiple-output (MIMO) antenna has been designed to operate at triple wide bands with improved port-isolation and polarisation diversity. The resonant modes of the MIMO are achieved by meander slot-loaded elliptical-shaped fundamental radiators, and the inter-port isolation is achieved by employing neutralising line-embedded ground plane. Apart from port-isolation, the proposed MIMO also offers polarisation diversity at different operating bands. The triple-band MIMO offers linear polarised radiation at WLAN band (4.2–5.6 GHz), right-hand circular polarised (RHCP) radiation at C-band (6.3–7.5 GHz) and left-hand circular polarised (LHCP) radiation at X-band (8.7–9.3 GHz). The overall isolation (>27 dB), envelope correlation co-efficient (ECC<0.0005), diversity gain (DG>9.9995), mean effective gain (MEG<0.734 dB), total active reflection co-efficient (TARC<−20 dB) and channel capacity loss (CCL<0.35 bits/S/Hz) meet the criteria for reliable MIMO operation. The proposed MIMO has been fabricated on a 55.6 × 55.6 × 1.6 mm3 piece of an FR-4 epoxy substrate after simulation and measured in VNA. Adequate similarity can be observed between the measured and simulated results. [ABSTRACT FROM AUTHOR]

A rectangular patch antenna with π shaped slot is proposed as a miniaturized antenna element with a gain of 5.83 dB for WLAN (5.2 GHz) application. This compact π shaped slot antenna is used as a radiating element for the design of a 2 × 1 MIMO system for WLAN application. A near field passive parasitic element is used in the proposed MIMO antenna to improve the isolation. The MIMO system has a surface area of 0.29λ2 with a measured gain of 6 dBi and impedance bandwidth of 110 MHz. The diversity characteristics of MIMO are quantified with envelop correlation coefficient of 0.004, capacity loss of 0.35 bits/s/Hz, mean effective gain ratio (less than 1), mutual coupling around −20 dB, and TARC is −14.5 dB. The measured results are in good agreement with the simulation results and validate the proposed design. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The current research work introduces a simple method to realize a circularly polarized patch antenna with 9.52% impedance bandwidth and axial ratio bandwidth. A modified T slot on the ground and offset feeding is used to achieve the required results. The antenna removes the need of complex feeding network for circular polarization and is fed by a microstrip line that makes it a good candidate to be integrated with planar circuits. The proposed antenna covers 2.3–2.53 GHz band with S11 < −10 dB and covers 2.12–2.53 GHz band with axial ratio <3 dB. This antenna is operated on practical 2.4 GHz ISM bands; this frequency band is very useful for wireless LAN, Bluetooth, GPS (IRNSS-1, S-Band), and other applications. The antenna is fabricated and the simulated and measured results are found to be in good agreement. [ABSTRACT FROM AUTHOR]

A novel frequency reconfigurable multiple-input multiple-output (MIMO) antenna, operating in triple and dual band, is presented for wireless local area networks (WLAN). The proposed antenna comprises of two planar inverted F antenna (PIFA) elements integrated with two PIN diodes. When diodes are ON, the proposed antenna operates at 2.4, 5.2 and 5.8 GHz with a maximum frequency ratio of 2.41. When diodes are OFF, it operates at 5.2 GHz, 5.8 GHz with a frequency ratio of 1.11. Meander line resonator and T slot achieve good isolation amid PIFA elements. The simulated and experimental characteristics are in good agreement. [ABSTRACT FROM AUTHOR]

A novel elliptically slotted antenna (ESA), with two notched bands for Ultrawideband (UWB) applications, is presented. The ESA comprises of an elliptically slotted radiator with a beveled defected ground structure (DGS) for achieving UWB bandwidth ranging from 3.42 to 11.79 GHz (110%) for VSWR< 2. Two rejected bands at WLAN (5.02–5.97 GHz) and down link of X- band (7.23–7.72 GHz) applications are obtained by etching S-shaped slot in the microstrip feed line and an asymmetrical C- shaped parasitic stub above the DGS, respectively. The ESA is printed on FR-4 substrate with a compact size of 24 × 28 m m 2 and with a stable gain fluctuation from 2 to 4.08 dBi. A good matching, achieved in-between tested and simulated results, makes ESA to be a suitable candidate for WLAN/X-band-notched UWB applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Although WiFi contributes little to total radiofrequency electromagnetic field (RF-EMF) exposure in our everyday environment, concern has raised whether this specific type of modulated RF-EMF causes health problems. The aim of this review is to evaluate all types of studies that investigated biological and health effects of WiFi exposure and fulfilled basic quality criteria. Eligible for inclusion were epidemiological, human experimental, in vivo and in vitro studies using realistic WiFi exposure settings. We conducted a systematic literature search for all papers published between January 1997 and August 2020 followed by a quality review addressing blinding and dosimetry in experimental studies and various types of biases in epidemiological studies. All studies fulfilling the quality criteria were descriptively summarized in terms of observation or absence of associations. From 1385 articles identified by the literature search, 23 fulfilled basic quality criteria: 6 epidemiological papers, 6 human experimental articles, 9 in vivo articles, and 2 in vitro articles. Whereas in vivo and in vitro studies applied exposure levels up to 4 W/kg, human studies dealt with exposure levels several orders of magnitude below the ICNIRP guidelines, which are typical for WiFi exposure situations in the everyday environment. Numerous outcomes ranging from biological markers to symptoms were mostly found not to be associated with WiFi exposure. Sporadic findings were not consistent in terms of outcomes or exposure-response associations. This review based on a systematic literature search and quality evaluation does not suggest detrimental health effects from WiFi exposure below regulatory limits. [ABSTRACT FROM AUTHOR]

In this contribution, novel design is presented for a very compact shielded quarter-mode substrate-integrated waveguide (S-QMSIW) based self-diplexing antenna (SDA) for WiMAX/WLAN applications. In order to achieve dual-band features, a slot is etched onto the top of the metal. Two orthogonal microstrip feed lines in the full-wave EM-simulator (HFSS) simulate the S-QMSIW resonator at two different frequencies (3.45 and 5.45 GHz). The proposed antenna pattern is extremely adaptable, allowing for simple frequency adjustments for each resonant frequency. A lumped circuit model is expected to be used to assess the antenna structure. A self-diplexing antenna based on S-QMSIW was designed, fabricated and tested to claim the proposed concept. At 3.45 and 5.45 GHz, the proposed antenna peak gains are 4.7 and 5.6 dBi, respectively. It offered port isolation better than 38 dB. The antenna front-to-back ratio was greater than 19.5 dB in each band. The proposed antenna circuit size was very compact ( 0.08 λ g 2 ). [ABSTRACT FROM AUTHOR]

This manuscript proposes a novel Ultra Wide Band (UWB) antenna in the dual-band rejection (DBR). The proposed technique is combination of hybridising Cat Swarm Optimisation (CSO) as well as Genetic Algorithm (GA); hence, it is called CSOGA technique. The UWB antenna is structured with 2.9–13.0 GHz frequency and to enhance the matching of impedance. The antenna type with size modification is determined by using optimisation algorithm. To attain the slits as well as strips band rejection in an antenna, the dual-band frequencies are rejected in 3.3–3.6 GHz as well as 5.15–5.825 GHz to band process of WiMAX, WLAN. Here, the efficiency of proposed technique is analysed by 10 standard benchmark functions (BF). The outcomes show that the proposed CSOGA technique gives 94% higher efficiency when likened to other techniques. [ABSTRACT FROM AUTHOR]

This paper presents a double-printed circular slot inscribed, hexagonal shape miniaturized dipole antenna featuring the ultra-wideband (UWB) characteristics with the implementation of linearly tapered feedline. The miniaturized UWB dipole antenna is designed for wireless applications wireless local area network (WLAN) and WiMAX by introducing a proposed metamaterial unit cell. Further, in comparison with the conventional UWB dipole antenna, miniaturization is achieved up to 35.89% and 16.67% with respective active patch area and antenna volume, respectively. The electrical dimension of the proposed antenna is 0.299 λ × 0.4385 λ × 0.0159 λ, of course, at lower frequency of 2.99 GHz. The use of metamaterial rectangular split-ring resonator and slotted ground structure witnessed the band achievements for wireless standards WLAN and WiMAX. The proposed structure is fabricated on FR4 substrate and tested. Impedance bandwidth of proposed antenna is obtained about 7.26% (2.39–2.57 GHz), 25.23% (2.91–3.75 GHz), and 16.92% (4.87–5.77 GHz) under simulation and 11.49% (2.38–2.67 GHz), 24.48% (2.94–3.76 GHz), and 15.99% (4.95–5.81 GHz) in measurement for WLAN (2.4–2.5, 5.150–5.250, and 5.725–5.825 GHz) and WiMAX (3.3–3.8 GHz) bands, respectively. Tunability between the wireless standards is demonstrated with the help of PIN diodes. The proposed design achieved high average gain of 3.31 and 2.06 dBi for simulation and measurement, respectively. The peak average radiation efficiency of 82.9% is observed during measurement mode. Experimental results are in good agreement with those obtained in the simulation of the proposed antenna. [ABSTRACT FROM AUTHOR]

Frequency reconfigurable circularly polarized (CP) fractal antennas are presented. At first, a fractal shaped slot is inscribed on the bigger size fractal structure. Inside the scratched opening, a small size asymmetrical fractal patch is embedded and switching diodes are brought along x and y – sides to attach these internal and external patches. By applying asymmetrical fractal curves as boundaries, imbalance is developed inside the structure for CP. The sizes of the inner and outer patches are chosen in the sort of manner to resonate the antenna at GSM (1.8 GHz), WLAN (2.45 GHz) and Wi-MAX (3.4 GHz) bands, respectively. The fractal curve parameters are optimized to enhance CP radiation. Four switches are used to govern the antenna. Measured and simulation outcomes are in near agreement, which proves that the suggested antennas are well ideal for WLAN/Wi-MAX, GSM/Wi-Fi, GSM/Wi-Fi/Wi-MAX applications. Similarly, several frequency reconfigurable antennas have been studied by using various fractal curves. [ABSTRACT FROM AUTHOR]

An ultra-wideband (UWB) antenna with quadruple-band-rejection characteristics and a size-miniaturised approach for portable wireless applications is designed and experimentally investigated. The proposed antenna consists of a unique trapezoidal-shaped patch, 50 Ω triple-step microstrip feed line and step–truncated ground plane. The patch tapering improves the bandwidth of an antenna to 2.8–12.5 GHz with fractional–bandwidth of 127%, covering an entire UWB (3.1–10.6 GHz). Consequently, it provides a nearly omnidirectional radiation pattern, better gain and excellent radiation efficiency. The three steps of the feed line increase the electrical length of the patch, achieving size reduction of the fabricated antenna to 20 mm × 29 mm. Generally, UWB systems suffer owing to strong narrowband signal interference from unlicensed wireless communication devices. To avoid this, the proposed antenna is designed with quadruple band-notch characteristics. It includes three inverted U-slots (length approaches half the guided wavelength), which are used to reject the 3.5, 4.5 and 5.2/5.8 GHz bands. Moreover, a C-strip pair besides the feed line is used to reject the 8.35 GHz X-band. The simulated results were also compared with the experimental performance of the prototype in terms of reflection coefficient, voltage standing wave ratio, radiation pattern, transfer function, group delay and gain of the antenna. [ABSTRACT FROM AUTHOR]

A high-gain broadband microstrip patch antenna using a PTFE substrate of dielectric constant 2.4 with a modified radiating patch is proposed. Two different shapes of ground planes (rectangular and circular) have been used under the proposed radiating patch to enhance the antenna gain. The lateral dimensions of the proposed patch are 0.52λ0 × 0.51λ0, where λ0 is the free space wavelength at f0 = 5.65 GHz. Here a total of five slits and a slot are embedded at the optimum position on the proposed patch. The effects of each slits on bandwidth and gain are demonstrated. The covered frequency band is 2 GHz (5.5–7.5 GHz). The achieved peak gains are 7 dBi at 5.65 GHz and 9 dBi at 7.5 GHz. The percentage bandwidth of 30.77 is achieved. It may be used in industrial, scientific and medical band, WLAN (5.8 GHz), WiMAX, and satellite communication applications. [ABSTRACT FROM AUTHOR]

This paper presents a compact triple-band and a multiband band-pass filter (BPF) using a stepped impedance line (SIL) and a modified stub-loaded open loop resonator (MSLOR), respectively. The first proposed triple-band BPF used a new technique which involves embedding the stepped impedance line (SIL) between the feed line and the open stubs. Due to this, the proposed filter achieves an ultra wideband (UWB) and two narrow bands with a fractional bandwidth of about 12.85%, 30.38% and 2.6% for use in 4G, WLAN and satellite communication. An UWB is generated with five transmission zeros that increase the high selectivity and avoid the interference between the existing bands. The second proposed filter is triple-band to multiband BPF using MSLOR. This filter achieves five passbands with seven transmission zeros. [ABSTRACT FROM AUTHOR]

This paper presents a highly compact dual-band elliptical wide-slot (EWS) antenna with high bandwidth dimension ratio (BDR) having one inverted L-slot for WLAN and WiMAX applications. Initially, the broadband characteristic of 4.4–9.3 GHz is obtained by using an EWS in the ground plane. To include 3.5 GHz WiMAX wireless standard, a parasitic elliptical patch is embedded in the centre of the elliptical wide-slot. With an increase in semi-major axis length of the parasitic patch, the overlapping capacitance between the microstrip-line and the parasitic patch increases, thereby showing a broadband characteristic ranging from 3.59 to 7.08 GHz and BDR of 1423. An inverted L-shaped slot is etched in the ground plane to generate a frequency band around 2.4 GHz, integrating the 2.4 GHz WLAN and 2.5 GHz WiMAX wireless standards. The measured 10 dB return loss bandwidth due to mirrored L-shaped slot is 440 MHz (2.34–2.78 GHz) with BDR of 923. As a result, the EWS with parasitic patch and mirrored L-shaped slot together gives an overall size of 0.132 λ L × 0.14 λ L where λ L is the lowest free-space wavelength corresponding to the operating frequency of 2.34 GHz. The measured peak gain of lower and upper-frequency bands is 6.95 and 6.82 dB. [ABSTRACT FROM AUTHOR]

This article presents a circularly polarized 4-port Multiple Inputs Multiple Outputs dielectric resonator-based antenna with two resonating bands for WLAN (5.0 GHz) and WiMAX (3.5 GHz) applications. Important attributes of proposed MIMO-DRA are: (i) Bandwidth enhancement is observed due to the use of ring-shaped ceramic material radiator; (ii) Incorporation of rectangular aperture lead to excite the dual hybrid mode in ring DRA, which helps to support dual-frequency range (iii) Circular polarization is achieved in both operating bands by conversion of rectangular to Z-shaped slot; and (iv) mutual coupling among port <−18 dB due to the use of space diversity. The fabricated prototype of the MIMO radiator is measured experimentally, which confirms the dual impedance bandwidth of 3.35 – 3.82 GHz and 5.09 – 5.41 GHz. The proposed antenna is right-handed circularly polarized (RHCP) within the frequency range of 3.54 – 3.72 GHz & 5.04 – 5.16 GHz respectively. [ABSTRACT FROM AUTHOR]

This article presents a novel compact folded Zeroth-Order Resonant (ZOR) antenna using concept of Composite Right/Left-Handed (CRLH) transmission line operating in the WLAN/ISM bands of 2.4 and 5.2 GHz for Internet of Things (IoT) applications including USB dongle and radio-frequency identification (RFID) systems. It consists of two-unit cells of a CRLH transmission line and operates in a series resonant mode with an overall size of 1.6 mm × 38 mm × 9 mm. The measured results show that fractional bandwidths of 11.34% and 3.9% for S11 < −10 dB, and radiation efficiencies of 64.89% at 2.4 GHz and 78.88% at 5.2 GHz are obtained. A comparison between our proposed work and other existing works shows the achievement of considerable antenna miniaturization using the technique of CLRH transmission line. The measured and simulated results are generally in good consensus. Being novel and compact, the proposed design is a potential candidate for diverse IoT devices including USB dongles and low-profile RFID tags. [ABSTRACT FROM AUTHOR]

An optically transparent antenna fabricated using conductive oxide thin film AgHT-8 is presented. The proposed antenna is compared with two other antennas made up of materials AgHT-4 and copper which form the patch and ground, respectively. Glass is used as a transparent substrate material having a relative permittivity of 5.5, loss tangent of 0.075 and thickness of 2 mm. The antennas have an overall dimension of 0.4λ×0.4λ mm2 at centre frequency of 2.4 GHz which is kept consistent for performance comparison. Measured return loss shows impedance bandwidth of the order 10.20% at 3.68 GHz and 5.12% at 5.52 GHz for AgHT-8, 9.71% at 3.77 GHz and 3.81% at 5.58 GHz for AgHT-4 and 8.42% at 3.79 GHz and 4.42% at 5.69 GHz for copper-based antenna. The radiation pattern of the transparent resonator using AgHT-8 has unidirectional and dipole-like pattern. The efficiency of the proposed antenna shows good resemblance with measured results, making the antenna suitable for WiMAX M3500T-01/04 (3.4GHz-3.8GHz) and IEEE 802.11a (America) applications. [ABSTRACT FROM AUTHOR]

A low-profile multi-input-multi-output (MIMO)/diversity antenna suitable for wireless local area network (WLAN) applications is presented. In the proposed antenna, two identical elements (each of size 20 × 47 mm2) are designed to operate at 2.4 GHz and other two identical elements (each of size 20.5 × 20 mm2) at 5.8 GHz. All elements of the proposed diversity antenna are printed on 1.6 mm thick FR-4 substrate in a coplanar configuration. By optimizing the distance between the antenna elements (in horizontal and vertical directions), optimal isolation and diversity performance are achieved. Compared to a single feed dual-band antenna, the MIMO/diversity antenna has the ability to transmit or receive the 2.4 and 5.8 GHz signals simultaneously, without any external switching circuit between the module and the proposed antenna. [ABSTRACT FROM AUTHOR]

A compact planar inverted-F antenna (PIFA) placed on one of the two hinges of a laptop computer is proposed for wireless local-area network (WLAN) operation. The aim of this design is to integrate the PIFA's metal surroundings as part of the radiating structure. When the PIFA is fed, resonant modes in the hinge slot bounded by the two hinges, display ground plane, and keyboard ground plane can in turn be excited. Since the 200 × 5 mm2 slot is much larger than the 10 × 5 mm2 PIFA itself, the latter, although compact and structurally simple, can be made efficiently radiating with the help of the former. Measured efficiencies are all over 50% in the desired three WLAN bands [ABSTRACT FROM AUTHOR]

There has been growing interest in indoor positioning system technologies due to the important role of real-time indoor positioning services in modern technologies such as security services and emergency healthcare. Currently, many large companies such as Apple, Microsoft, and Google have researched location-based services (LBS), as they are key for network optimization and extensive computing applications. Multiple techniques were proposed using fingerprinting-based location methods due to their ability to obtain accurate results within several meters. However, their major drawback is that the received signal strength (RSS) can fluctuate with time and different environment, giving RSS distribution a multimodal distribution. Thus, in this paper, we established a framework consisting of k-mean-symmetrical-Hölder-divergence, a statistical model that encapsulates Cauchy-Schwarz divergence and skews Bhattacharyya divergence, to measure dissimilarities among signals that have multivariate distributions. In other words, the traditional k-mean is extended to meta-algorithms to detect the cluster that RSS is related to. Our second approach was hierarchical Bayesian model based on adaptive lasso criterion to recover sparse signals to optimize the accuracy of the indoor location estimation by solving the l1-minimization problem. The experimental results showed that the proposed system had substantially improved localization estimation accuracy compared to traditional fingerprinting-based localization methods. [ABSTRACT FROM AUTHOR]

A flexible, spiral-shaped frequency reconfigurable antenna with a compact size (20 × 24 mm2) is presented. The proposed antenna has a low-profile planar structure and is able to operate at five different frequency bands, i.e., 4.19–4.48, 5.98–6.4, 3.42–4.0, 5.4–5.68, and 6.8–7.0 GHz. The multiband operation enables the antenna to cover aeronautical radio navigation, fixed satellite communication, WLAN, and WiMAX standards. A radiating element is backed by Rogers® 5880 substrate with a thickness of 0.508 mm and dielectric constant of 2.2. The spiral shape is achieved by introducing different strips. Frequency reconfiguration is achieved by the incorporation of a lumped element in a strip, so that the antenna can switch between different resonances. To validate the performance of the antenna, the prototype of the design was fabricated and tested. Good acquiescent is seen between simulated and measured results. The proposed antenna operates efficiently with appreciable return loss, directivity, bandwidth, and peak gain. [ABSTRACT FROM AUTHOR]

In this paper, a single-layer dual-band dual-sense circularly polarized monopole antenna is presented for Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The proposed antenna consists L, U shape strips and a 50 Ω microstrip feedline. This antenna is printed on one side of low-cost FR4 epoxy substrate with a thickness of 1.6 mm and partial ground plane is on the other side of the substrate. The overall dimension of the substrate is 0.417λ0 × 0.292λ0 × 0.0133λ0. The antenna may operate in two bands: the lower band is from 2.35 to 3.22 GHz, centred at 2.52 GHz (percentage bandwidth od 34.52%) and the upper band is from 4.78 to 5.79 GHz, centred at 5.49 GHz (percentage bandwidth of 18.39%). In addition, 3 dB axial ratio bandwidth of the lower and upper bands are 650 and 650 MHz, respectively. The detailed performances of the proposed antenna are demonstrated along with the measured and simulated results. [ABSTRACT FROM AUTHOR]

In this paper, a compact and low-loss diplexer is designed and fabricated using integrated passive device (IPD) technique. This IPD-based diplexer can be utilized in antenna system for WLAN and WiMAX applications. It is composed of a low-pass filter and a high-pass filter, built on the GaAs substrate with the overall size of 0.95 × 0.95 mm2. The IPD diplexer realizes a dual-mode operation of 2.4 GHz for WLAN and 3.3 GHz to 3.8 GHz for WiMAX, respectively. The measurement results match well with the simulation results, in which the insertion loss at operation bands are below 0.5 dB (2.4 GHz) and 0.64 dB (3.3 GHz to 3.8 GHz), and the stopband suppression keeps higher than 20 dB. [ABSTRACT FROM AUTHOR]

A 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. [ABSTRACT FROM AUTHOR]

A novel flexible pattern reconfigurable antenna for WLAN wireless system is proposed. The reconfigurable antenna is fed by a microstrip, and consists of a circular monopole patch, three ship-shaped parasitic patches, a planar ground and two parallel symmetrical parasitic branches embedded with two PIN diodes. The antenna achieves two-state pattern reconfigurability by controlling the on and off of two PIN diodes to change the director. The antenna has a bandwidth of 2.40-2.48 GHz and is capable of steering the beam in the direction 30°, 330° in the azimuthal plane. Meanwhile, the antenna works at two states with the same band. Finally, the bending characteristics of the antenna at different bending degrees are analyzed. Measured results are in good agreement with simulations, which denotes that it is suitable for WLAN wireless systems. [ABSTRACT FROM AUTHOR]

A new slim microstrip antenna with a narrow ground plane and dual-band operation for global positioning system (1575.42 MHz), Glonass-L1 (1600 MHz), long-term evaluation (1700 MHz), GSM (1800 MHz) and WLAN/near-field (2450 MHz) applications is presented. The antenna consists of a simple rectangular patch, a shorting pin and a meander-line (ML) which has a strip-like shape to be easily mounted inside the portable devices. The lower-band covers 1540-1850 MHz while the upper-band stands in 2.44-2.46 GHz. [ABSTRACT FROM AUTHOR]

In this article, a dual-band half split cylindrical dielectric resonator antenna is proposed for multiple-input multiple-output (MIMO) applications. The dual-band operation is achieved by simultaneously exciting and modes in an aperture coupled fed half split cylindrical dielectric resonator. The topology of four element MIMO antenna is such that it provides both spatial and polarization diversities. Over both the operating bands, the measured port-to-port isolation is better than 20 dB. The proposed antenna exhibits broadside radiation with cross polarization level below dB in both xz- and yz-plane. The peak gain of antenna is 4.88 and 5.32 dBi at lower and upper operating frequency, respectively. The MIMO performance of the proposed antenna is found to be good with ECC0.06. Moreover, the channel capacity of the proposed MIMO is near to uncorrelated case for uniform propagation scenario. The proposed antenna could be suitable for LTE 22/LTE 42 and WLAN applications. [ABSTRACT FROM AUTHOR]

Wireless local area networks (WLANs) are widely deployed for internet-centric data applications. It is predicted that by 2018, about two-thirds of the world's internet traffic will be video, and more than half of the traffic will be offloaded to Wi-Fi networks. Consequently, WLANs need major improvements in both throughput and efficiency. New technologies continue to be introduced for WLAN applications for this purpose. The IEEE 802.11ac standard is the currently implemented amendment by the IEEE 802.11 standard working group that promises data rates at gigabits per second. The main features of the IEEE 802.11ac standard are adopting increased bandwidth and higher order modulation than the previous standard, and multiple-input multiple-output (MIMO) and multi-user MIMO transmission modes. These features are designed to improve the user experience. In addition to technologies that enhance the efficiency of the WLAN, the IEEE 802.11ax standard is also investigating and evaluating advanced wireless technologies to utilize the existing spectrum more efficiently. These modern communications technologies are steadily advancing physical layer data rates in WLANs, although data throughput efficiency of the WLAN may degrade rapidly as the physical layer data rate increases. The fundamental reason for the degradation is that the current medium access control (MAC) protocol allocates the entire channel to one user as a single source due to equally distributed time domain contention resolution. The challenges and difficulties have already been identified for designing efficient MAC layer resource allocation (MAC-RA) schemes for the upcoming IEEE 802.11ax high-efficiency WLAN. However, there is no profound investigation outcome for this kind of efficient resource allocation. Therefore, in this paper, we conduct an extensive survey of the expected features and challenges for IEEE 802.11ax in the design of fair and efficient MAC-RA. The associated previous research work is summarized as to future directions. Moreover, the need for each directed scheme is highlighted. [ABSTRACT FROM AUTHOR]

Recent surge in the development of wireless communication has increased the need of the antennas that can operate at more than one frequency band. To meet the requirements, reconfigurable antennas are used. This paper presents design and analysis of a low profile, planar and, frequency reconfigurable E-shape patch antenna, using a 1.6 mm thicker FR-4 substrate. The antenna operates in two single-band and two dual-band modes, depending on the status of the two switches. The proposed antenna works efficiently (>90%) with an adequate gain (>2 dBi) and bandwidth (430 MHz-1 GHz) in the desired frequency bands {WiFi (2.45 GHz), WiMAX (3.59 GHz), WLAN (5.2 GHz), Military/NATO (4.5 GHz), C-Band (6.22 and 6.27 GHz)}. The antenna is optimally matched (VSWR < 1.45) in all these six frequency bands. The proposed antenna is compact in size (40 × 35 mm2) and can be used in portable electronic devices to support multiple wireless services. The antenna is analysed in computer simulation technology, microwave studio (CST MWS). The prototype is fabricated and measurements are conducted to validate the simulations. [ABSTRACT FROM AUTHOR]

A novel planar switchable antenna with a band-notched and multi-resonance performance is proposed. In order to generate single band-notched characteristics, a parasitic element with attaching two stubs is applied. Furthermore, to achieve a switchable function, only one PIN diode is used across a semicircular radiator patch and the parasitic element. When the PIN diode is biased forwardly, the semicircular patch transforms to a circular patch, and an additional resonance is excited at the notch frequency. Additionally, by attaching two L- and T-shaped stubs and cutting a rectangular slit on the radiating patch, new additional resonances are excited, and hence wider impedance bandwidth can be produced. The presented antenna has a compact size of 19.5 × 17 mm2, equal to 0.2 λ0× 0.17 λ0(λ0is the free-space wavelength at 3.1 GHz). The experimental and simulated results show that the antenna has a good radiation behavior within the ultra-wideband frequency range (3.08 to over 14 GHz) and reconfigurable frequency band-notched function in the range of wireless local area network and dedicated short-range communication signals (4.87–6.08 GHz). It is shown that there is virtually no change in the antenna's E-plane and H-plane radiation patterns for the various PIN diode switching conditions, especially at low frequencies. [ABSTRACT FROM AUTHOR]

This paper presents compact printed UWB antenna (2.75-16.5 GHz) with WLAN band-notch at 5.75 GHz (4.1-7.1 GHz), the overall size of the antenna (46 × 27) mm2 base on FR-4 substrate with relative permittivity 4.4 and low profile of 1.6 mm, the gain has maximum value of 4.5dBi and minimum value of −3.32dBi at 12.5 GHz and Band-Notch frequency 5.75 GHz, respectively, with very good radiation pattern characteristic has been achieved. [ABSTRACT FROM AUTHOR]

In this article, techno-economic analysis of a fiber-wireless access network is presented. With high bandwidth capacity of the gigabit passive optical network and with cost-effectiveness of very high throughput 802.11ac wireless local area networks that enable user mobility in the wireless segment, fiber-wireless access networks can be considered as an alternative to the fiber-to-the-home architecture for next generation access networks. Analysis based on the proposed scenario here, shows that a fiber-wireless access network is a more cost-effective solution in densely populated areas, but with some introduced improvements, even other geotypes can be considered as a commercially-viable solution. [ABSTRACT FROM AUTHOR]

This paper presents the design of compact and low profile multi-band/reconfigurable planar monopole antennas using a 1.6 mm-thicker FR4 substrate and a truncated ground-plane. One of the proposed structures (Antenna2) is reconfigured using optical switch. The proposed antennas can operate in single- and dual-band modes depending on the STATE of the switch. Antenna1 operates in dual-band mode (Wi-Fi @ 2.45 GHz and WLAN @ 5.4 GHz). Antenna2 gives two distinct dual-band modes depending on the state of the switch, i.e. (Wi-Fi @ 2.45 GHz and WLAN @ 5.13 GHz) and (WiMAX @ 3.49 GHz and WLAN @ 5.81 GHz), when the switch is ON and OFF, respectively. The proposed structures achieve bandwidths ranging from 11% to 36% at respective centred frequencies. The antennas are designed with input impedance in the range of 45–53 Ω having VSWR < 1.27 for operating frequency bands. Gain values from 1.6 to 3 dBi and radiating efficiencies from 76.4% to 92% are attained at required operating bands. The proposed antennas are light-weight, low-profile, and easily fabricated. Therefore, they are potential candidates for use in portable and intelligent mobile phones, laptops, PDAs, and iPads as well as for military, rescue, safety, and medical applications. Using a numerical Finite Integration Technique employed in Computer Simulation Technology Microwave Studio, the antennas far-field, scattering, and gain parameters are evaluated. The antennas are fabricated and a good agreement between the measured and simulated results is observed. [ABSTRACT FROM AUTHOR]

A single feed dual-band miniaturized microstrip patch antenna for Wireless Local Area Network (WLAN) communications has been proposed. The outer rectangular loop patch and inner modified E-shaped patch were used to resonate at 2.4 and 5 GHz, respectively. In order to separate the effect between two frequency bands, a shorting pin was set between two resonance cells. The simulated results show that it can operate at 2.4 and 5 GHz bands with 0.072 GHz (2.407–2.479 GHz) and 0.715 GHz (5.137–5.853 GHz) fractional bandwidth, respectively, which can cover the whole frequency band of WLAN. In addition, the antenna is miniaturized by 31% compared to the conventional rectangular patch without a slot. At last, the proposed microstrip patch antenna has been fabricated and measured for both impedance matching and radiation patterns. A comparison of the measurement and simulation results is given, which show reasonable good agreement. [ABSTRACT FROM AUTHOR]

This article presents a compact, enhanced bandwidth, and variable dual band notched printed monopole antenna for ultra wideband (UWB) applications. By inserting a simple inverted L-shaped slot in the ground plane and modifying the lower edge of the patch, wider bandwidth with usable fractional bandwidth of 139.2% (3.1–17.3 GHz) is achieved whereas two inverted U-shaped slots in the corner modified patch are embedded to realize two notch bands exactly at WiMAX (3.25–3.75 GHz) and WLAN (5.1–5.9 GHz). A precise design formula is also proposed to calculate the length of the slots. The proposed simple antenna structure with a 50 Ω feed line has been obtained within a small size of 0.11λ × 0.19λ. The simulated results are validated using measured results to show potentiality of the proposed antenna structure in UWB applications. [ABSTRACT FROM PUBLISHER]