Fractal Antenna Research Articles

A compact circular polarized patch fractal antenna for global navigation satellite systems

AbstractA circular polarized square fractal patch antenna with square slot and via is proposed, which can be applied to global navigation satellite systems. Two pairs of square ring slot with different sizes are placed diagonally for antenna circularly polarized radiation. By changing the square patch into a fractal structure and adding defective ground structure, miniaturization can be achieved while the bandwidth is further expanded. The total antenna size is 0.3λo × 0.3λo × 0.03λo (λo is the free‐space wavelength at 1.575 GHz). The final measurement results show that the maximum gain is 3.26 dBic, the 3 dB axial ratio (AR) bandwidth is 1.57–1.6 GHz and the impedance bandwidth (S11 < −10 dB) is more than 60 MHz at the resonant frequency of 1.575 GHz.

Improvement of Coplanar Vivaldi Antenna Radiation Patterns with Fractal Structure for Ultra-Wideband Applications

The need for telecommunications technology requires fast data transfer and increasing capacity. Therefore, telecommunications technology continues to be developed by creating transmitter and receiver devices that can work at Ultra-Wideband (UWB) frequencies. This study aims to design a coplanar Vivaldi antenna with a fractal structure so that the performance of the antenna radiation pattern can increase to apply UWB frequency. The conventional coplanar Vivaldi antenna, model-A, and Model-B fractal antennas are designed to see the performance of return loss values less than -10 dB, VSWR less than 2, and working frequency of 2-10 GHz. The fractal model is created with a circular repeating structure given at the edges of the antenna patch. From the simulation results, the main lobe value of the conventional Coplanar Vivaldi antenna was 5.21 dBi, the model-A fractal was 7.02 dBi, and the Model-B fractal was 7.84 dBi. The order of the best sidelobe performance at a frequency of 6 GHz is obtained for the model-A fractal of -9 dB. Beamwidth of 46 degrees and the best main lobe direction of 0 degrees is obtained for fractal model-B. By adding a fractal structure, the lobe magnitude/directivity, sidelobe level, beamwidth, and main lobe direction can be improved

Application of Theory of Characteristics Modes for Bandwidth Enhancement of a Miniaturized Minkowski Fractal Antenna

This article presents a miniaturized modified Minkowski fractal antenna with enhanced linearly polarized impedance bandwidth (IBW) in the lower frequency region. Applying theory of characteristic modes (TCM) analysis on a second iterated modified Minkowski radiator without feeding structure, modal currents and their corresponding modal fields (radiation patterns) were determined to recognize symmetric dominant modes to be specifically excited to generate the required radiation pattern. It gave direction for choosing quarter-wave microwave line feeding as the feed of choice to excite the four desired modes at 2.7, 5.7, 5.9, and 8.7 GHz and providing excellent impedance matching to generate the very wide IBW. Measured results matched well with simulations done using Ansys HFSS 2020R1. Measured IBW is 9.7 GHz (160%), from 1.2 to 10.9 GHz, with center resonance frequency (frc) at 6.05 GHz, whereas simulated IBW is 9.4 GHz (162%), from 1.1 to 10.5 GHz with frc at 5.8 GHz. The antenna size is 36 × 34 × 1.6 mm3 (0.216λgL × 0.204λgL where at lower resonating frequency frL = 1.1 GHz, λgL is the guided wavelength) with 82.24% reduction in size. This antenna may be utilized for “L”, “S” band and UWB wireless communication.

Dual-Band Single-Layer Fractal Frequency Selective Surface for 5G Applications

Due to the global growth in popularity of Fifth Generation (5G) cellular communications, the demand for shielding against it has risen for a variety of applications, mainly related to cybersecurity but also to isolation, calm areas and so on. This research paper aims to provide a suitable dual-band fractal FSS (Frequency Selective Surface) for the 5G lower band frequencies: 750 MHz and 3.5 GHz. The unit cell is in the shape of a bow tie, where each of the triangular parts are Sierpiński triangles. One major addition to the unit cell is a central metal strip to make the manufacturing of the FSS more feasible and to tune the operation frequencies and bandwidths. As with each different stage of a fractal antenna, the different stages of the fractal FSS design behave differently. For this application, stage 2 is sufficient, as we are able to cover frequency bands among those included in the FR1 5G spectrum. Some equations were derived using linear regression in order to provide specific design tools for building an FSS. These equations have high accuracy and can be used to adapt the proposed design to other frequencies. Some other parameters, which are not represented in the aforementioned equations, can also be adjusted for minor tweaking of the final design. This design performs well except under large incidence angles. This should be taken into account when proposing the installation of a structure based on it. A good agreement between simulation and measurement results is observed.

A novel miniaturized Koch-Minkowski hybrid fractal antenna

PurposeAntenna miniaturization, multiband operation and wider operational bandwidth are vital to achieve optimal design for modern wireless communication devices. Using fractal geometries is recognized as one of the most promising solutions to attain these characteristics. The purpose of this paper is to present a unique structure of patch antenna using hybrid fractal technique to enhance the performance characteristics for various wireless applications and to achieve better miniaturization.Design/methodology/approachIn this paper, the authors propose a novel hybrid fractal antenna by combining Koch and Minkowski (K-M) fractal geometries. A microstrip patch antenna (MPA) operating at 1.8 GHz is incorporated with a novel K-M hybrid fractal geometry. The proposed fractal antenna is designed and simulated in CST Microwave studio and compared with existing Koch fractal geometry. The prototype for the third iteration of the K-M fractal antenna is then fabricated on FR-4 substrate and tested through vector network analyzer for operating band/voltage standing wave ratio.FindingsThe third iteration of the proposed K-M fractal geometry results in achieving a 20% size reduction as compared to an ordinary MPA for the same resonant frequency with impedance bandwidth of 16.25 MHz and a directional gain of 6.48 dB, respectively. The operating frequency of MPA also lowers down to 1.44 GHz.Originality/valueFurther testing for the radiation patterns in an anechoic chamber shows good agreement to those of simulated results.

A novel compact fractal UWB antenna with dual band notched characteristics

A novel compact fractal UWB antenna with dual band notched characteristics

A Novel Multi-band High-Gain Slotted Fractal Antenna using Various Substrates for X-band and Ku-band Applications

A Novel Multi-band High-Gain Slotted Fractal Antenna using Various Substrates for X-band and Ku-band Applications

Pentagon inscribed circular superwideband fractal MIMO antenna

SummaryA compact circular fractal antenna element loaded with a central pentagonal slot is presented in this paper. This structure consists of a fourth iterative radiator fed by a partially tapered feed line and CPW defected ground plane. A superwide impedance bandwidth of 3.45–52.17 GHz (~175% fractional bandwidth) is achieved. Two multiple input multiple output (MIMO) configurations are also designed and analyzed by using this antenna element. For spatial and pattern diversity configurations, the impedance bandwidth of 3.45–52.2 and 3.1–52.2 GHz are achieved, respectively. The optimized footprints of antenna element, spatial diversity configuration, and pattern diversity configurations are 28 × 24, 28 × 53, and 45 × 48 mm2, respectively. The isolation for both MIMO configurations is more than 20 dB in maximum portion of the operating bandwidth. Desirable radiation and diversity performance characteristics are achieved for antenna element and MIMO configurations. The wide bandwidth, compact dimensions along with good radiation, and diversity performance characteristics make the proposed antenna configurations suitable for integration in superwideband wireless communication systems. A good agreement between the experimental and simulation results is observed.

A Novel Metamaterial Inspired 2nd Iteration Koch Fractal Antenna for Wi-Fi, WLAN, C band and X band Wireless Communications

The rapid advancements in wireless technology desires compact, miniaturized, multiband and ultra wideband antennas. Fractal antennas have been proved as a source for fulfilling these demands. In this paper a 2nd order Koch fractal antenna of size 29.6 × 35.7mm2 designed on FR4-epoxy substrate material of dielectric constant (ɛr) 4.4 with a height of 1.6mm. This antenna is named as ANTENNA-1. To increase this antenna’s performance a meta material unit cell has been placed on the ground plane to serve multi band applications and is named as ANTENNA-2, which is the proposed antenna in this paper. The simulations have been carried out for both the antennas using ANSYS HFSS tool over the frequency sweep of (1-12GHz). The simulation results of proposed antenna producing 7 frequency bands which serves Wi-Fi, WLAN, C-band, and X band wireless communications. The simulation results like return loss, VSWR values have a good matching with the measured return loss, VSWR results of the fabricated antenna

Research of a Fractal Microstrip Antenna Based on the Modified Minkowski Curve of the Second Iteration

Evolving telecommunications systems require modern antennas with improved performance. The creation of miniature antennas with a high gain, multi-band properties and defined polarization is an urgent task. New challenges in the reception and emission of electromagnetic waves are being solved in different ways. The use of fractals in the construction of antennas is becoming widespread. This article presents the results of a study of fractal microstrip antenna of the second iteration based on the Minkowski geometry. The main parameters such as the reflection coefficient, directivity and efficiency are described. Resonance frequencies and directional patterns at these frequencies as well as bandwidths are shown. Conclusions concerning the possibility of using this type of antenna in various applications are drawn.

A Novel Compact Magneto-Electric Dipole Antenna for Millimeter-Wave Beam Steering Applications

A novel compact magneto-electric (ME) dipole antenna with size of 0.31λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.31λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.12λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at central frequency herein and after), gain of around 8 dBi, and bandwidth of 39.7% is presented for millimeter-wave beam steering applications with the combination of the fractal technique and reactive impedance surface (RIS) loading. In particular, a fractal ME dipole antenna with four modified second-order Minikowski structures is firstly designed, where an aperture size of 0.38λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.38λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is achieved. Herein, the antenna gain is dropped with the size reduction. Then a capacitive RIS structure is designed and loaded to improve the antenna gain and further lower down the antenna operating frequency range. With the RIS structure, the antenna gain is increased by around 4 dB, and the operating center frequency is shifted to left side by 9.0 GHz, thus achieving a further size reduction. Simulation and measurement results are provided to demonstrate the excellent properties of the proposed antenna. Subsequently, the antenna is arranged into a 5 mm-spaced (half wavelength at 30 GHz) 16-element uniform linear array. The beam steering characteristics of the array are investigated with the influence of phase quantization errors into consideration.

English

In this paper, a hexagonal fractal antenna is proposed for wireless applications. The basic shape of the fractal antenna is a hexagon which is modified by inserting smaller hexagons along the periphery of the generator structure. The proposed antenna exhibits a bandwidth of 7.5 GHz in the frequency range of 3.3-10.8 GHz. The band notch for WLAN rejection at 5.75 GHz is obtained by etching hair-pin slot in the feed structure of the antenna. The fractional bandwidth of the antenna is 53.33 and 55.62% and the VSWR obtained at the notch frequency of 5.75 GHz is 5.2 which are highly suitable for wireless communication. Key words: Fractal antenna, Ultra wide-band (UWB), VSWR, notch, hair-pin slot.

A novel wideband fractal rectangular dielectric resonator antenna with improved radiation performance

A wideband fractal rectangular dielectric resonator antenna (RDRA) based on the hook-shaped dipole is proposed for wireless communication, which exhibits stable, symmetric radiation patterns and low cross-polarization. The antenna consists of a Koch-like fractal rectangular dielectric resonator antenna (FRDRA) and a hook-shaped electric dipole (HSE-Dipole), which are equivalent to the magnetoelectric (ME) dipoles. The symmetrical radiation pattern with gain enhancement and suppression of backward lobe is achieved by the complementary combination of the electric and magnetic dipoles. The Koch-like fractal structure is used to improve the impedance matching of the RDRA with 15% size reduction. The antenna is excited by the substrate integrated waveguide (SIW) feeding network, which takes the advantage of compact size and low insertion loss. Due to the air gap between the FRDRA and HSE-Dipole, the fundamental TE1δ1 and high-order TE1δ2 modes of the RDRA are both generated to obtain the 19.5% impedance bandwidth. The prototype is fabricated and measured to validate the antenna design, which shows remarkable radiation performance including the front to back ratio (FTBR) of >20 dB, the average gain of 5.96 dBi and low cross-polarization.

Потапов Александр Алексеевич (к семидесятилетию со дня рождения)

Is presented the information about Alexander A. Potapov - Dr Sci Phys@Math, chief researcher in Kotelnikov Institute of Radioengineering and Electronics of RAS, academician of Russian Academy of Natural Sciences, the well-known scientist in the field of radiophysics and radar, statistical radio engineering, recognition and processing of images and signals, fractal and texture analysis, fractional operators, fractal electrodynamics, fractal antennas and deterministic chaos.

A Novel Energy Harvesting Antenna Design for Battery-less IoT devices

Energy harvesting is a process in which small amounts of energy are captured from radiative radio frequencies (RF) that would otherwise be lost as heat, light, sound, or movement. The captured energy allows improving the efficiency of wireless communications, where it enables new technologies such as battery-less devices or power internet of things (IoT) devices without the need for batteries. This paper presents a novel antenna design, called an icosahedron-Sierpiński fractal monopole antenna, where the advantage of such a geometry is in its ability to capture a wide range of frequencies due to its multi-band characteristic and three-dimensional characteristics. The performance of the antenna has been evaluated by numerical simulations and compared with the already existing research. The proposed antenna geometry has been designed using AUTOCAD2020 and simulated on COMOSOL 5.4 to operate at frequencies between 0.84GHz, 1GHz, 1.6 GHz, 2.4GHz, and 3GHz.

Gain Enhancement of Miniaturized Fractal Antenna with Help of Complementary Fractal Lens

Gain Enhancement of Miniaturized Fractal Antenna with Help of Complementary Fractal Lens

A Novel Approach of Design and Analysis of a Hexagonal Fractal Antenna Array (HFAA) for Next-Generation Wireless Communication

The study and exploration of massive multiple-input multiple-output (MMIMO) and millimeter-wave wireless access technology has been spurred by a shortage of bandwidth in the wireless communication sector. Massive MIMO, which combines antennas at the transmitter and receiver, is a key enabler technology for next-generation networks to enable exceptional spectrum and energy efficiency with simple processing techniques. For massive MIMOs, the lower band microwave or millimeter-wave band and the antenna are impeccably combined with RF transceivers. As a result, the 5G wireless communication antenna differs from traditional antennas in many ways. A new concept of the MIMO tri-band hexagonal antenna array is being introduced for next-generation cellular networks. With a total scaling dimension of 150 × 75 mm2, the structure consists of multiple hexagonal fractal antenna components at different corners of the patch. The radiating patch resonates at 2.55–2.75, 3.45–3.7, and 5.65–6.05 GHz (FR1 band) for better return loss (S11) of more than 15 dB in all three operating bands. The coplanar waveguide (CPW) feeding technique and defective ground structure in the ground plane have been employed for effective impedance matching. The deviation of the main lobe of the radiation pattern is achieved using a two-element microstrip Taylor antenna array with series feeding, which also boosts the antenna array’s bandwidth and minimizes sidelobe. The proposed antenna is designed, simulated, and tested in far-field radiating conditions and generates tri-band S-parameters with sufficient separation and high-quality double-polarized radiation. The fabrication and testing of MIMO antennas were completed, where the measurement results matched the simulation results. In addition, the 5G smartphone antenna system requires a new, lightweight phased microwave antenna (μ-wave) with wide bandwidth and a fire extender. Because of its decent performance and compact architectures, the proposed smartphone antenna array architecture is a better entrant for upcoming 5G cellular implementations.

Complementary split-ring resonator and strip-gap based metamaterial fractal antenna with miniature size and enhanced bandwidth for 5G applications

This paper proposes two different types of metamaterial (MTM) antennas for fifth-generation (5G) mid-band frequency operation. The radiating patch of the proposed antenna is based on the combined Minkowski-Sierpinski carpet fractal structure. On the ground plane, two different types of MTM structures: Complementary split-ring resonator (CSRR), and Strip-gap are etched to enhance the overall bandwidth and gain of the antenna. The introduction of these structures on the ground plane also leads to antenna miniaturization. Both the proposed MTM structure based antennas resonate at 3.5GHz. The overall size of the two fabricated prototypes is 28×29.5 mm2 / 28×28.5 mm2, which shows the compactness of the proposed design by 43% / 42% as compared to the conventional microstrip patch antenna (MPA). The measured bandwidth/gain achieved by the proposed combined Minkowski-Sierpinski carpet fractal antenna (CMSFA) having CSRR MTM and strip-gap etched on the ground plane are 370 MHz / 2.42dBi and 440 MHz / 3.75dBi, respectively.

Design and Analysis of Multiband Fractal Antenna for MIMO/Diversity Applications

Design and Analysis of Multiband Fractal Antenna for MIMO/Diversity Applications

Opportunistic control of fractal‐based MIMO antenna for sub‐6‐GHz 5G applications

SummaryThe proposed research work is on fractal MIMO antenna with microstrip feeding for lower sub‐6 GHz. The design construct's goal is to improve the isolation among the patches and is constructed with a combination of circular strip and rectangular strip slots, and rectangular slots are introduced on the ground plane. The fractal‐shaped MIMO structure composes of FR‐4 material and compact size of 25 × 35 mm2. The current 2 × 1 fractal MIMO radiator resonates at a frequency 3.5 GHz for lower sub‐6‐GHz applications with directional radiation patterns. In this structure, the performance characteristics of design antenna parameters like S‐parameters, surface current distributions, and radiation pattern of the fractal MIMO radiator are investigated. In addition to antenna parameters, MIMO parameters like diversity gain (DG), mean effective gain (MEG), channel capacity loss (CCL), total active reflection coefficient (TARC), and time‐domain analysis parameters are also evaluated. It has been observed that the MIMO parameters of the antenna are in the acceptable range. Fractal‐based prototype MIMO structures are fabricated as well as tested for effective radiation and impedance. The improvised MIMO design that's been installed on a printed circuit board with connector, device housing, compact size, and various types of housing shows better performance compared to the conventionally designed antennas.