Showing papers on "Fractal antenna published in 2015"

A Compact Koch Fractal UWB MIMO Antenna With WLAN Band-Rejection

Abstract: In this letter, a compact octagonal shaped fractal ultrawideband multiple-input–multiple-output antenna is presented, and its characteristics are investigated In order to achieve the desired miniaturization and wideband phenomena, self-similar and space filling properties of Koch fractal geometry are used in the antenna design These fractal monopoles are placed orthogonal to each other for good isolation Moreover, grounded stubs are used in the geometry to provide further improvement in the isolation The band rejection phenomenon in wireless local area network band is achieved by etching a C-shaped slot from the monopole of the antenna The proposed antenna has compact dimensions of $45~\hbox{mm} \times 45~\hbox{mm}$ and exhibits quasi-omnidirectional radiation pattern In addition, it shows an impedance bandwidth ( ${{\rm S}_{11}}\! ) from 2 to 106 GHz with isolation better than 17 dB over the entire ultra-wideband range Diversity performance is also evaluated in terms of envelope correlation coefficient and capacity loss The measured results show good agreement with the simulated ones

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

Abstract: This letter presents the design of a dual-band wearable fractal-based monopole patch antenna integrated with an electromagnetic band-gap (EBG) structure. The prototype covers the GSM-1800 MHz and ISM-2.45 GHz bands. The EBG structure reduces the radiation into the human body over 15 dB. It also reduces the effect of frequency detuning due to the human body. The performance of the antenna under bending, crumpling, and on-body conditions has been studied and presented. Specific absorption rate (SAR) assessment has also been performed to validate the antenna for its usefulness in wearable applications.

Design and Synthesis of Multilayer Frequency Selective Surface Based on Antenna-Filter-Antenna Using Minkowski Fractal Structures

Abstract: A multilayer frequency selective surface (FSS) with subwavelength fractal elements based on the antenna-filter- antenna (AFA) concept is proposed in this paper. The upper fractal patches are inductive and non-resonant, and the fractal slots on the ground provide a capacitance. The thin substrate is equivalent to a transformer and some resonant modes are produced. Multiple transmission poles are obtained by cascading multilayer two-dimensional periodic structure array of the fractal patches and slots on the ground. The cell periods along $x$ and $y$ directions are the same and the total height is 8 mm, and the fractional bandwidth reaches 30% at normal incidence. To analyze and understand the operating mechanism of the FSS, the equivalent circuit model (ECM) is proposed to analyze the transmission and reflection characteristics. The results of the synthesis from ECM agree well with the results of full-wave simulation. The multilayer AFA-FSS has been manufactured and measured to verify the effectiveness and correctness of the design and synthesis. The simulated results are in good agreement with the tested ones.

Gain enhancement of bow-tie antenna using fractal wideband artificial magnetic conductor ground

Abstract: A novel fractal wideband artificial magnetic conductor (AMC) structure is designed as the ground plane of a printed bow-tie antenna for gain enhancement and low profile. The origin printed bow-tie antenna is operated in the range from 1.67 to 2.06 GHz for a VSWR <2. The AMC structure consists of 6 × 9 first-order fractal unit cells that are made up of four circles and four smaller circles, and the ±90° reflection phase band is 1.1–3.03 GHz. Both the AMC ground plane and bow-tie antenna are fabricated and measured. The distance between the antenna and the AMC is reduced to one-eighth of the wavelength in free space at 1.7 GHz. The experimental results show that the composite antenna has a wide bandwidth from 1.64 to 1.94 GHz, with a relative frequency bandwidth of 16.7%.

A Dielectric Resonator-Loaded Minkowski Fractal-Shaped Slot Loop Heptaband Antenna

Abstract: A multiband fractal co-planar waveguide (CPW)-fed slot antenna loaded with a dielectric resonator conforming to multiple wireless standards is presented in this paper. The Minkowski fractal geometry is utilized to generate multiple frequency bands as well as to provide a miniaturized design compared to its Euclidean counterpart. The idea behind placing the dielectric load is to serve a dual purpose of enhancing the impedance bandwidth of the antenna at the upper frequency band as well as improving the overall gain of the antenna. The slot loop acts as a hybrid antenna performing the task of both an antenna as well as a feed mechanism for the dielectric slab to radiate. Design guidelines involving closed form formulae and equivalent model consisting of lumped resonators, distributed resonators and impedance transformers of the dielectric-loaded fractal slot antenna are provided to present an insight into the functioning of the antenna. The reflection coefficient parameters of the antenna yield a close match between the circuit model and those obtained from full wave simulator. The proposed antenna exhibits a heptaband performance with a maximum gain of 3.1 dBi.

Low-Profile Compact Circularly-Polarized Antenna Based on Fractal Metasurface and Fractal Resonator

Abstract: A novel low-profile and compact circularly-polarized (CP) antenna has been proposed and comprehensively investigated based on the combination of fractal metasurface and fractal resonator. The Hilbert shaped reactive impedance surface has improved the antenna performance in terms of low substrate thickness and good front-to-back ratio, and the Wunderlich-shaped fractal complementary split ring resonator with strong space-filling property achieves the CP property and further size reduction. For application, a CP antenna working at the Wimax band is numerically and experimentally studied. The results indicate that the proposed antenna achieves a compact layout of $40~\hbox{mm} \times 45~\hbox{mm} \times 2.5~\hbox{mm}$ at 3.5 GHz, a relative wide bandwidth of more than 1.86% and also a comparable gain of about 6.3 dBic. The strategy does not require any metallic via holes, sophisticated feeding networks or truncated corners, predicting promising applications in portable communication systems.

Design and testing of a compact circularly polarised microstrip antenna with fractal defected ground structure for L-band applications

Abstract: A compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492-1.518 GHz) is presented. Two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation. To improve the performance parameters of patch antenna such as axial ratio (AR) bandwidth, return loss bandwidth, radiation efficiency and so on a new technique of combination of fractal theory and defected ground structure (DGS) is proposed for the first time in design of CP antennas. 44.74% size reduction in patch size, enhancements of 62.73% in AR bandwidth, 70.74% in return loss bandwidth and 4.03% in radiation efficiency is achieved as compared with conventional patch antenna, after incorporation of Koch curve fractal DGS in the ground plane. The performance of the developed antenna has been compared with other available L-band planar antennas in the literature, and it is found that the developed structure is better one in many aspects. Laboratory prototype of the antenna is fabricated and experimentally measured for cross verifying the simulated results.

Circularly Polarized Spidron Fractal Dielectric Resonator Antenna

Abstract: In this letter, a circularly polarized Spidron fractal dielectric resonator antenna is presented. A wide 3-dB axial ratio (AR) bandwidth is realized by merging a Spidron fractal dielectric resonator and a C-shaped slot that can produce circular polarization. The proposed antenna is excited through the coupling between a C-shaped slot in the ground plane and a ${\hbox {50-}} \Omega $ microstrip feeding line. A prototype of the antenna is fabricated and tested. Reasonable agreement is achieved between the measurement and simulation. The experimental results show that the proposed antenna has a $-$ 10- $\hbox{dB}$ reflection bandwidth of 37.29% (4.32–6.30 GHz) and a 3-dB AR bandwidth of 11.57% (5.13–5.76 GHz). The measured gain of the antenna ranges 2.20 dBic to 3.16 dBic within the AR bandwidth.

Miniaturized UWB Log-Periodic Square Fractal Antenna

Abstract: In this letter, the log-periodic square fractal geometry is presented for the design of a miniaturized patch antenna for the ultra-wideband (UWB) services (3.1-10.6 GHz). A miniaturization factor of 23% is achieved with a constant and stable gain in the desired band. The radiation pattern is broadside, which finds suitable applications in the UWB radars and medical imaging. Furthermore, the time-domain performance of the proposed antenna is investigated. A prototype model of the proposed antenna is fabricated and measured as a proof of concept.

CPW fed hexagonal micro strip fractal antenna for UWB wireless communications

Abstract: This paper presents the hexagonal microstrip fractal antenna (HMSFA) for ultra wideband wireless communication applications. Hexagonal antenna is powered through co-planar waveguide (CPW) feed structure. The stepping fed configuration is used to improve the antenna electrical characteristics at the centre and higher frequencies in the FCC designed UWB frequency range from 3.1 to 10.6 GHz. The proposed antenna uses a fractal technique to analyze its UWB characterization. The hexagon antenna is designed, simulated and fabricated on a polyamide substrate of dielectric constant ɛ r = 4.3, thickness t = 1.53 mm, loss tangent tan δ = 0.004 and lande G factor 2. The operating bandwidth of the proposed fractal antenna is about 9 GHz more than UWB range. The size of the radiating patch is about 26 mm × 30 mm and the sided length s = 15 mm, achieves good impedance matching, constant gain, steady radiation patterns, multi resonant and constant group delay over an UWB frequency range from 3.1 to 10.6 GHz. This antenna creates the fractal geometry inside the patch with similar in shape but different in sizes. The proposed antenna is fabricated and experimental results are verified in an anechoic chamber of millimetre and antenna lab.

Miniaturised microstrip bandpass filters based on Moore fractal geometry

Abstract: This paper presents new microstrip bandpass filter design topologies that consist of dual edge-coupled resonators constructed in the form of Moore fractal geometries of second and third iteration levels. The space-filling property for proposed fractal filters has found to produce reduced size shapes in accordance with sequential iteration levels. These filters have been prepared for ISM band applications at a centre frequency of 2.4 GHz using a substrate with a dielectric coefficient of 10.8, dielectric thickness of 1.27 mm and metallisation thickness of 35 µm. The output responses of each fractal bandpass filter have been determined by a full-wave-based electromagnetic simulator Sonnet software package. Simulated and experimental results are approximately compatible with each other. These responses clarify that these fractal filters have good transmission and return loss characteristics with blocked higher harmonics in out-of-band regions.

Design of fractal based microstrip rectangular patch antenna for multiband applications

Abstract: In this paper a multiband fractal based rectangular microstrip patch antenna is designed. FR4 substrate having thickness of 1.58 mm is used as substrate material for the design of proposed antenna and microstrip feed line provides the excitation to the antenna. The antenna operating frequency range is from 1 to 10 GHz. The proposed antenna resonate at twelve different frequencies as 1.86, 2.33, 3.67, 4.57, 5.08, 6.06, 7.03, 7.75, 8.08, 8.84, 9.56 and 10 GHz and the return losses are −15.39, −16.48, −10.02, −17.29, −13.15, −23.41, −10.22, −11.28, −17.02, −10.94, −15.15 and −15.48 dB respectively. The proposed antenna is designed and simulated by using the Ansoft HFSS V13 (high frequency structure simulator) software.

Bandwidth enhancement of a CPW-fed monopole antenna with small fractal elements

Abstract: In this paper, a technique of adding small fractal elements to the polygon shape radiator of a CPW-fed monopole antenna for bandwidth enhancement is proposed and experimentally studied. Based on the multi-resonance effect of the fractal elements, three closely spaced resonant frequencies are produced over the antenna bandwidth which leads to coverage of the standard UWB bandwidth (3.1–10.6 GHz). Effects of increasing the number of the polygon sides on S 11 and radiation patterns are also investigated. Finally, three prototypes of the proposed antenna are fabricated and measured in order to verify the simulation results.

Miniaturised printed elliptical nested fractal multiband antenna for energy harvesting applications

Abstract: This study presents the design, optimisation, simulation and fabrication of a novel printed elliptical nested fractal (planar) antenna for multiband operation. The proposed antenna is intended to function as the receptor element in radio-frequency energy harvesting applications. The simple microstrip structure and the compact size of the antenna ease its fabrication and allow it to be integrated with other electronic circuitry. It consists of nested elliptical structures fed by 50 Ω microstrip line with complementary elliptical ground along with rectangular ground plane. The added Hilbert structures at both sides of the antenna feeding line on the top layer enhance its performance to operate in multi-frequency bands. This antenna exhibits good radiation and reflection characteristics at 910 MHz (global system of mobile (GSM 900)), 2.4 GHz (Bluetooth/wireless local area network), 3.2 GHz (Radiolocation, third generation (3G)), 3.8 GHz (for long-term evolution, 4G) and additional 5 GHz band (wireless fidelity signals). The overall dimension of antenna is 41 mm (width) × 44 mm (length) × 1.778 mm (thickness). To the best knowledge of the authors, this is the widest bandwidth antenna to be developed at these small dimensions covering major standards from 900 MHz up to 6 GHz for electromagnetic energy harvesting applications.

Circularly Polarized Broadband Antenna Deploying Fractal Slot Geometry

Abstract: This letter introduces a new method of achieving broad VSWR bandwidth and axial ratio bandwidth (ARBW) deploying fractal geometry in a single feed compact annular slot antenna loaded with diagonal slots. Various studies have been carried out for different iteration order (IO) and iteration factor (IF) on antenna performance. A measured VSWR bandwidth (2:1) of 400 MHz (1.37 GHz to 1.77 GHz) and measured ARBW of 360 MHz (1.47 GHz to 1.83 GHz) is achieved. A measured peak gain of 6.6 dB is reported at 1.775 GHz. This antenna can be applied to handheld devices applications and WSN node positioning requiring GPS Data.

A Novel Tri-Band Hexagonal Microstrip Patch Antenna Using Modified Sierpinski Fractal for Vehicular Communication

Abstract: The present paper analyses and documents the merits of incorporating fractal design in microstrip antenna intended to be mounted on and integrated into the design of smart vehicles. A novel design is proposed for a compact tri-band hexagonal microstrip antenna to be integrated with the body of a smart vehicle for short range communication purpose in an Intelligent Transport System (ITS). This antenna can be used at 1.575 GHz of GPS L1 band for vehicle to roadside communication, at 3.71 GHz of mobile WiMAX band (IEEE 802.16e-2005) for blind spot detection and at 5.9 GHz of DSRC band (IEEE 802.11p) for vehicle to vehicle communication. At 3.71 GHz, the two major lobes of the antenna radiation beam, tilted by 35 ◦ on both sides from its broadside direction, help the vehicle to detect blind spots efficiently. The largest dimension of the proposed antenna corresponds to the lowest resonating frequency, 1.575 GHz. Compared to the conventional hexagonal patch, the modified Sierpinski fractal proposed herein reduces the overall area, at 1.575 GHz, by 75%, with 5.2 dBi gain. In comparison with other popular fractals, the proposed fractal structure achieves demonstrably better antenna miniaturization. When the antenna is mounted on the vehicle, considered an electromagnetically larger object, the simulated and on-vehicle experimental results show antenna gains of more than 5.5 dBi at 1.575 GHz, 8 dBi at 3.71 GHz and 9 dBi at 5.9 GHz in the desired direction with negligible amount of electromagnetic interference inside the car.

A Compact Multiband Hybrid Fractal Antenna for Multistandard Mobile Wireless Applications

Abstract: This paper presents a compact Multiband hybrid fractal antenna designed for mobile wireless applications it has planar structure and suitable for mobile applications at low cost. The proposed antenna structure is obtained by integrating a Koch curve and Minkowski curve. It exhibits multiband behavior, acceptable values of return loss, VSWR and gain in-spite of its compact size and less complexity. The proposed antenna design has been examined up to 2nd iteration of the new fractal geometry. The simulated results exhibited seven bands of operation covering some important frequency bands like GPS (L1 = 1227.60 MHz), bluetooth (2.41---2.49 GHz) of ISM band, WLAN 802.11 a/b (5.15---5.35 GHz) and other bands covers applications like mobile/fixed satellite and aeronautical navigation (3.876---4.375, 6.6188---7.0045, 7.9698---8.3373 and 9.1648---9.6214 GHz). Proposed antenna is designed by using scripting method of HFSS using MATLAB.

A compact octagonal fractal UWB MIMO antenna with WLAN band‐rejection

Abstract: In this article, a compact octagonal-shaped fractal ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna is presented and its characteristics are investigated. The application of Koch fractal geometry at the edges of octagonal monopole provides desired miniaturization and wideband phenomena due to its self-similar and space filling properties. The two octagonal fractal antennas are placed orthogonal to each other and used to construct UWB MIMO antenna. An L-shaped stub is used in the ground plane of the geometry to provide an improvement in the isolation. The band rejection in wireless local area network band is achieved by etching a C-shaped slot from the monopole of the individual antenna. The compact dimension 40 × 25 mm2 of the antenna exhibits nearly omnidirectional radiation pattern, a low envelope correlation coefficient (<0.01), with good S-parameters over the entire UWB frequency range. The measured results show good agreement with the simulated one. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1919–1925, 2015

Miniaturisation of the triangular patch antenna by the novel dual-reverse-arrow fractal

Abstract: A novel geometry called the dual-reverse-arrow fractal (DRAF) is introduced, which is the combination of two dual Koch fractals It is implemented on an equilateral-triangular patch antenna This structure has smaller dimensions compared to the rectangular structure and has wide applications in arrays to reduce their size Furthermore, the use of triangular elements in array leads to the decrease of side-lobe levels Four cases of the triangular patch are compared to show that the presented fractal geometry is effective in the miniaturisation of patch antenna and decreasing its resonance frequency, while the antenna bandwidth and efficiency are kept constant To increase the antenna efficiency, an air space is placed under the patch Finally, a portion of the corner of fractal triangle is cut to generate circular polarisation by proper positioning of the feed points The proposed DRAF antenna achieved 40% reduction in size compared to the similar triangular antenna The proposed DRAF geometry has potential applications in various radiating systems and microwave devices

Super-wideband textile fractal antenna for wireless body area networks

Abstract: In this study, a novel textile fractal antenna is designed and optimized using genetic algorithm for super-wideband applications. The antenna design is based on the iterations of triangular–circular patch and a partially modified elliptical ground plane. Results show that the proposed antenna presents impedance bandwidth (return loss < −10 dB) covering the range of frequencies from 1.4 to 20 GHz. The present design mainly focuses on the current trends in the development of wireless body area networks for many wireless communications such as GPS, PCS-1900, IMT-2000/UMTS, WiFi, Bluetooth, and UWB applications.

Design and Performance Study of Sierpinski Fractal Based Patch Antennas for Multiband and Miniaturization Characteristics

Abstract: Modern wireless communication systems demand for compact and miniaturised antennas which are capable of operating at multiple frequency bands. Cutting fractals on traditional geometry and using them as antennas for such applications have a wide scope of research. In this work, Sierpinski geometry based patch antenna is considered for multiband operation and miniaturisation of the radiating element. The characteristics of the fractal based antennas are investigated as a function of fractal iteration. The fabricated prototypes are used to validate the simulated results.

Design of super wideband hexagonal-shaped fractal antenna with triangular slot

Abstract: A hexagonal-shaped fractal antenna with triangular slot for super wideband (SWB) application is presented. The proposed antenna has total size of 20 × 33.4 × 1.57 mm3.The proposed antenna is designed of iterations of triangular slot on a hexagonal metallic patch with tapered microstrip line feed. A combination of semicircular and rectangular shaped partial ground plane is used to achieve a super wide bandwidth from 3 to 35 GHz with bandwidth ratio of 11.6:1. The antenna design, simulation and optimization are performed using IE3D Full Wave Electromagnetic Simulator. The proposed antenna is compact and has stable radiation pattern. The simulation and measured results are compared to demonstrate the performance of proposed antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1659–1662, 2015

Inner tapered tree-shaped fractal antenna for UWB applications

Abstract: In this article, a compact third iteration inner tapered tree-shaped fractal antenna for ultrawideband applications is presented. The bandwidth is enhanced by using CPW ground plane and increasing the number of iterations. An impedance bandwidth of 4.3–15.5 GHz (113%) is achieved. The proposed third iteration antenna has nearly omnidirectional patterns at its resonance frequencies with an acceptable value of gain. The experimental and simulation results are found to be in good agreement. The proposed antenna has improved return loss performance and miniaturized size. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:559–567, 2015

Metamaterials Applied to ESPAR Antenna for Mutual Coupling Reduction

Abstract: Phased array smart antennas are becoming the primary choice for wireless communication solutions. Along with the increased usage of this technology, the problems related to mutual electromagnetic coupling between elements become evident. On arrays consisting of only one active element and multiple parasite elements (which steer the radiation pattern), as is the case of the electronically steerable passive array radiator (ESPAR) antenna, it is desirable to have maximum mutual coupling between each parasite element and the active one. However, the mutual coupling between parasite elements decreases the overall efficiency of the adaptive algorithm used to optimize the radiating pattern of the array. This letter explores the use of metamaterial as a near-field electromagnetic insulator. A novel ESPAR antenna structure, composed by metamaterial between parasite elements, has been proposed. The metamaterial structure transforms the conventional behavior of electromagnetic waves. The wave–metamaterial interaction behaves as a high-impedance area, which attenuates electromagnetic waves that move across it. The results show an effective minimization of the mutual coupling between the passive elements, with no significant impact to the mutual coupling between the active element and each passive one.

Simple, Compact, and Multiband Frequency Selective Surfaces Using Dissimilar Sierpinski Fractal Elements

Abstract: This paper presents a design methodology for frequency selective surfaces (FSSs) using metallic patches with dissimilar Sierpinski fractal elements. The transmission properties of the spatial filters are investigated for FSS structures composed of two alternately integrated dissimilar Sierpinski fractal elements, corresponding to fractal levels , 2, and 3. Two FSS prototypes are fabricated and measured in the range from 2 to 12 GHz to validate the proposed fractal designs. The FSSs with dissimilar Sierpinski fractal patch elements are printed on RT/Duroid 6202 high frequency laminate. The experimental characterization of the FSS prototypes is accomplished through two different measurement setups composed of commercial horns and elliptical monopole microstrip antennas. The obtained results confirm the compactness and multiband performance of the proposed FSS geometries, caused by the integration of dissimilar fractal element. In addition, the proposed FSSs exhibited frequency tuning ability on the multiband frequency responses. Agreement between simulated and measured results is reported.

A modified coaxial probe-fed Sierpinski fractal wideband and high gain antenna

Abstract: This paper deals with modified Sierpinski fractal wideband antenna design. As research in the field of antenna design has already established, therefore it is exceptional that a novel approach is used over conventional antenna design methods to optimize the existing Sierpinski fractal antenna. The implemented antenna exhibits the broadband behaviour in the frequency bands of 12.2–13.4 GHz and 21–30 GHz in which it follows S 11 ≤ −10 dB all through the frequency bands. The measured peak gains within the specified frequency bands vary from 8 to 22 dB. This high gain is achieved by employing the modifications to the initial Sierpinski geometry. The experimental and measured results of the modified coaxial probe fed Sierpinski fractal antenna are also presented. Experimental results are also validated.

Dual-broadband dielectric resonator antenna based on modified Sierpinski fractal geometry

Abstract: A novel dual-broadband dielectric resonator antenna (DRA) is presented. The proposed antenna has realised both dual-band and wideband features by applying the modified Sierpinski structure to the antenna design of the proposed DRA. The measured impedance bandwidths for │S 11 │ < −10 dB are 2.25–2.6 GHz (14.46%) and 3.1–4.1 GHz (27.78%), which can cover the wireless local area network (WLAN, 2.4–2.484 GHz) and the worldwide interoperability for microwave access (WiMAX, 3.4–3.69 GHz) bands. Meanwhile, stable radiation patterns and gains of about 5 and 3.8 dBi at 2.4 and 3.5 GHz, respectively, have been observed.

A quad-band hybrid fractal antenna for wireless applications

Abstract: Hybrid fractal multiband antenna is designed using Koch and meander geometry and its characteristics are investigated. The proposed antenna helps to achieve multiband behavior due to its multiple resonance characteristics. It has planar structure, compact size and suitable for wireless applications. IFS approach has been used to obtain the hybrid structure using MATLAB and scripting method of HFSS. Perturbation of basic structure is done to achieve quad-band behavior. Proposed antenna resonates at four different frequencies including Bluetooth (2.12–2.95 GHz), WLAN (4.82–5.95 GHz), 4.07 GHz and 7.3 GHz. It is a low cost antenna designed on easily available FR4 substrate. It exhibits nearly omnidirectional radiation pattern and VSWR ≤ 2 for all resonating frequencies.