Fractal Antenna Array Research Articles

Circularly polarized 2 × 2 fractal antenna array for space borne tracking applications

A corporate feed sequentially rotated 2 × 2 circularly polarized fractal antenna array is investigated in this work. Four number of compact circular fractal antenna elements are positioned symmetrically across the geometry. The antenna elements in the subarray are incorporated with 1st order Koch fractal cuts and rotated with respect to its neighbor and the phase change thus generated becomes offset with the phase change in the excitation in the corporate feed. A 2nd order Minkowski fractal curve is implemented on the ground plane to optimize the radiation performance of the array. The proposed fractal antenna array (FAA) is powered with a coaxial feed, with its pin connected to the asymmetric line configuration placed on the top surface. The dimensional confinement of the array is limited to 0.904λ0 × 0.876λ0 × 0.012λ0 (fr = 2.27 GHz) and the overall layout of the geometry is built on a FR4 substrate having a dielectric constant of 4.4. The circularly polarized radiation characteristics of the elements are developed as a result of fractal cuts along the vertical and horizontal sides. A maximum gain response of 5.4 dBic is observed in the impedance band ranging from 2 GHz to 2.5 GHz. The measured results of the proposed array are found to be in good agreement. In quantitative comparison with a few existing arrays with respect to its diverse performance the proposed CP FAA is found to be suitable for space-borne applications operating in the S-band.

Wideband 4-port MIMO antenna array using fractal and complimentary split-ring structure for Ku-band appliances

This article presents the wideband compact 4-port fractal MIMO antenna array for Ku-band applications. It incorporates the Koch snowflake fractal in combination with a complementary split-ring resonator (CSRR) to achieve both miniaturization and a broad bandwidth. Further, to improve the effectiveness of the single-driven element, the 2-element linear array is constructed, fabricated, and tested. The single-driven element and the constructed array give good performance results. For pattern diversity, a 4-port MIMO configuration is developed and tested. The proposed MIMO array geometry realizes a wide bandwidth of 13.6−17.5 GHz, fractional bandwidth of 25.08%, a maximum gain of 6.95 dBi, and radiation efficiency of beyond 90% with superior isolation (>−30 dB). It provides better diversity performance parameters (Envelope correlation coefficient <0.001) over the resonating band. Also, channel capacity loss (CCL) <0.11 bit/s/Hz and the total active reflection coefficient (TARC) <−10 dB, parameters are perceived to be within adequate range. Therefore, the designed compact fractal antenna, 2-element array, and 4-port MIMO array are applicable for wide Ku-band applications.

Soft Computing Techniques for Feed Position Optimization of Circular Shaped Fractal Antenna Array

Soft Computing Techniques for Feed Position Optimization of Circular Shaped Fractal Antenna Array

Comparison of Microwave Hyperthermia Applicator Designs with Fora Dipole and Connected Array.

In microwave hyperthermia tumor therapy, electromagnetic waves focus energy on the tumor to elevate the temperature above its normal levels with minimal injury to the surrounding healthy tissue. Microwave hyperthermia applicator design is important for the effectiveness of the therapy and the feasibility of real-time application. In this study, the potential of using fractal octagonal ring antenna elements as a dipole antenna array and as a connected array at 2.45 GHz for breast tumor hyperthermia application was investigated. Microwave hyperthermia treatment models consisting of different fractal octagonal ring antenna array designs and a breast phantom are simulated in COMSOL Multiphysics to obtain the field distributions. The antenna excitation phases and magnitudes are optimized using the global particle swarm algorithm to selectively increase the specific absorption rate at the target region while minimizing hot spots in other regions within the breast. Specific absorption rate distributions, obtained inside the phantom, are analyzed for each proposed microwave hyperthermia applicator design. The dipole fractal octagonal ring antenna arrays are comparatively assessed for three different designs: circular, linear, and Cross-array. The 16-antenna dipole array performance was superior for all three 1-layer applicator designs, and no distinct difference was found between 16-antenna circular, linear, or cross arrays. Two-layer dipole arrays have better performance in the deep-tissue targets than one-layer arrays. The performance of the connected array with a higher number of layers exceeds the performance of the dipole arrays in the superficial regions, while they are comparable for deep regions of the breast. The 1-layer 12-antenna circular FORA dipole array feasibility as a microwave hyperthermia applicator was experimentally shown.

Minkowski–Sierpinski Fractal Structure-Inspired 2 × 2 Antenna Array for Use in Next-Generation Wireless Systems

In this paper, the design, simulation, fabrication, and characterization study of a low-cost and directional hybrid four-element (2 × 2 configuration) Minkowski–Sierpinski fractal antenna array (MSFAA) for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the sub-6 GHz 5G wireless system is presented. Each element of the array is separated by 0.7 λ0. The complete four-element fractal antenna array system includes designing the single-element Minkowski–Sierpinski fractal antenna using two different substrates for performance comparison and an equal-split Wilkinson power divider (WPD) to achieve power division and to form a feed network. The single-element antenna, four-element fractal antenna array, and WPDs are fabricated using a flame-resistant (FR4) glass epoxy substrate with a dielectric constant (εr) of 4.3 and thickness (h) of 1.66 mm. For performance comparison, a high-end Rogers thermoset microwave material (TMM4) substrate is also used, having εr = 4.5 and h = 1.524mm, respectively. The designed four-element fractal antenna array operates at the dual-band frequencies of 4.17 and 5.97 GHz, respectively. The various performance parameters of the antenna array, such as return loss, bandwidth, gain, and 2D and 3D radiation patterns, are analyzed using CST Microwave Studio. The fabricated four-element antenna array provides the bandwidth and gain characteristic of 85 MHz/4.19 dB and 182 MHz/9.61 dB at 4.17 and 5.97 GHz frequency bands, respectively. The proposed antenna array design gives an improvement in the bandwidth, gain, and radiation pattern in the boresight at both frequencies. In the IEEE 802.11 ax WLANs (Wi-Fi 6E) deployments and the upcoming 5G wireless and satellite communication systems, it is critical to have directional antenna arrays to focus the radiated power in any specific direction. Therefore, it is believed that the proposed dual-band four-element fractal antenna array with directional radiation patterns can be an ideal candidate for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the upcoming 5G wireless and satellite communication systems.

Design of Multiband Fractal Antenna Array for Wireless Communication

This work proposes a modified circular fractal antenna array for multiband applications, including WLAN (5.15–5.85 GHz), C-band applications (3.8–4.4 GHz), and X-band for satellite communication (7.1–7.76 GHz). High Frequency Structure Simulator (HFSS) is used to simulate the antenna. The substrate material is FR4 epoxy, which has a 4.4 relative permittivity and 1.6 mm of thickness. It is discovered that the antenna only covers a portion of the bandwidth of the aforementioned applications.

Fractal geometry-based chakra-shaped microstrip patch antenna array for vehicular communications under 5G environments

ABSTRACT In this paper, fractal geometry-based two-printed antenna structures are proposed for vehicular communication in 5G wireless communication networks. Initially, a 48 × 39 mm2 single element fractal patch antenna is designed and tested which shows dual-band resonance at around 28.1 and 32.5 GHz. In order to improve different antenna characteristic number of fractal radiating elements have been increased to four and constructed an array of patches such that it can be used for multiple applications in the field of vehicular communications. The proposed array model is fabricated on a Rogers RT duroid 5880tm material of size 115 × 82 mm2 and tested using Agilent Technologies N5247A VNA. The measured results confirm the validity of the designed model for intended applications. The proposed array antenna operates at distinct quintuple bands in the frequency range of 25–36 GHz for vehicular communication within the proposed lower fifth generation (5G) channel. The proposed array configuration shows a good peak gain of 6.72 dB within the operating bands.

A New Adaptive Beamforming of Multiband Fractal Antenna Array in Strong-Jamming Environment

This paper proposes, for the first time, a new radiation pattern synthesis for fractal antenna array that combines the unique multi-band characteristics of fractal arrays with the adaptive beamforming requirements in wireless environment with high-jamming power. In this work, a new adaptive beamforming method based on discrete cbKalman filter is proposed for linear Cantor fractal array with high performance and low computational requirements. The proposed Kalman filter-based beamformer is compared with the Least Mean Squares (LMS) and the Recursive Least Squares (RLS) techniques under various parameter regimes, and the results reveal the superior performance of the proposed approach in terms of beamforming stability, Half-Power Beam Width (HPBW), maximum Side-Lobe Level (SLL), null depth at the direction of interference signals, and convergence rate for different Signal to Interference (SIR) values. Also, the results demonstrate that the suggested approach not only achieves perfect adaptation of the radiation pattern synthesis at high jamming power, but also keep the same SLL at different operating frequencies. This shows the usefulness of the proposed approach in multi-band smart antenna technology for mobile communications and other wireless systems.

Design of the Gradually Defect Patch Fractal Array Antenna for Unmanned Aerial Vehicle

This paper creatively proposes a new fractal iterative structure of a gradual defect patch and combines it with a rectangular array structure. Aiming at the performance requirements of the UAV system for multi-band compatible antennas, a gradual defect patch fractal array is designed. The radiation performance of the fractal array antenna was simulated by the method of moments, and antenna samples were made and the radiation performance was tested. Both simulation and actual measurement results show that this antenna has a working bandwidth of 5.5 GHz or more, a minimum return loss as low as -44 dB and excellent omnidirectional radiation capability. This antenna is compatible with the GPS system frequency band, Beidou system frequency band, all working frequency bands of the second to fifth generation mobile communication systems and the three working frequency bands of the RFID system, and is expected to be widely used as an unmanned aerial vehicle system antenna.

Design and Analysis of DGS Based Miniaturized Compound Reconfigurable Asymmetrical Micro Strip Fractal Array Antenna for L, S and C Band Applications

Design and Analysis of DGS Based Miniaturized Compound Reconfigurable Asymmetrical Micro Strip Fractal Array Antenna for L, S and C Band Applications

Rhombus-Inscribed Circular Ring Fractal Array Antenna for Millimeter-Wave 5G Applications

A 1 × 4 planar fractal array antenna is designed and presented for millimeter-wave 5G applications. The array’s top side is made up of a rhombus-inscribed circular ring fractal patch radiator, while the backside is made up of a square notch-loaded partial ground plane. To achieve high gain, a 1 × 4 corporate feeding network is used to excite the array elements. The designed array has an overall size of 28 × 17.75 mm2. From simulations as well as experimental results, it is observed that the designed array offers a wide impedance bandwidth in the frequency range of 22.8–29.2 GHz. Furthermore, a peak gain of 10.7 dBi with a radiation efficiency of &gt; 95% is observed in the operating bandwidth.

Synthesis of Wideband Thinned Eisenstein Fractile Antenna Arrays With Adaptive Beamforming Capability and Reduced Side-Lobes

A modern design of fractal antenna arrays, called fractile array, which exhibits a fractal boundary contour within a tiled plane, is explored for enhanced array performance. In this paper, the Eisenstein fractile array is introduced to exploit the unique geometrical features of fractiles that allow multiband and wideband operation and avoid grating lobes in the radiation pattern even, in some cases, when the array elements’ spacing is greater than the half wavelength. To alleviate the large number of elements and the high Side-Lobe Level (SLL) occurred at large scales, the Genetic Algorithm (GA) optimization technique is considered for thinning the proposed antenna array by estimating the optimal set of “on” and “off” elements corresponding to the minimum SLL without degrading the directivity of the radiation pattern. Also, the proposed array configuration is designed with adaptive beamforming capability using the Least Mean Square (LMS) technique. The effectiveness of the proposed GA-LMS approach is investigated by performing several MATLAB simulations under various set of array configurations. Results reveal that the suggested thinned Eisenstein fractile antenna array using GA-LMS approach is superior in terms of multiband and wideband performance, array element reduction, SLL reduction, grating lobe elimination, and beamforming capability. This elucidates the robustness of the suggested thinned Eisenstein fractile array as a promising design for multiband, wideband, compact, inexpensive, and adaptive smart antennas in modern wireless systems.

Design and Analysis of Single Layer Proximity Fed Sierpinski Fractal 2x1 Array Antenna Embedded on Hexagon Shaped Patch with Defected Ground Structure

A novel innovative technique for producing a single layer proximity fed triple band antenna based on second iteration level Sierpinski fractal geometry implanted on a hexagonal shaped array antenna is being presented for next-generation cellular networks. The steps of fractal array antenna growth are examined. The array antenna is supplied using a single layer proximity fed method. The suggested single layer proximity fed hexagonal shaped array antenna with defective ground structure is developed and simulated using CST Microwave Studio, and characteristics such as bandwidth, return loss, directivity, and radiation pattern are investigated. The second iteration level single layer proximity fed array antenna's simulated -10 dB impedance bandwidth for the lower band is 237 MHz (1.6480 – 1.8850 GHz) with peak resonance at 1.8010 GHz, the middle band bandwidth is 66 MHz (2.4280 – 2.4940 GHz) with peak resonance at 2.4640 GHz, and the upper band bandwidth is 69 MHz (2.9080 – 2.9778 GHz) with peak resonance at 2.9 This antenna may be used for a wide range of wireless communication applications.

Investigation and Implementation of Integrated SIW System for Hexagonal Diamond of Lamda Shape Slots Fractal Array Antenna for X and KU-Band Applications

Investigation and Implementation of Integrated SIW System for Hexagonal Diamond of Lamda Shape Slots Fractal Array Antenna for X and KU-Band Applications

A MIMO Radar System based on Fractal Antenna Arrays for Level Measurement Applications

Abstract. In this contribution, the design of a multiple-input multiple-output (MIMO) radar system in 77–81 GHz range with 18 transmitting antennas and 24 receiving antennas for measuring the height profile of bulk solids in silos, is presented and discussed. The antenna array topologies are optimized by utilizing space filling fractals in order to approximate a circular shaped antenna array on a hexagonal grid. The proposed MIMO radar system achieves an angular resolution of 3.1∘ for a maximum scanning angle of ±45∘ and a side lobe suppression of 12.6 dB. The performance of the system has been evaluated by test measurements on a sand heap, showing an improved measurement accuracy compared to conventional radar level systems.

Design of a 1×2 CPW Fractal Antenna Array on Plexiglas Substrate with Defected Ground Plane for Telecommunication Applications

In this paper, a fractal antenna array for telecommunication applications is presented. The proposed antenna array is realized on a Plexiglas substrate, has 1×2 radiating elements, and dimensions of 170mm×105mm. The antenna array is composed of two Koch Snowflake patches and is fed by a Coplanar Waveguide (CPW) transmission line. Radiating elements and the ground plane are printed on the top side of the substrate. Defected Ground Structure (DGS) technique is employed to enhance the bandwidth and improve the impedance matching. The proposed antenna array operates at two frequency bands, 1.08-1.32GHz covering the GPS band and 1.7-3.7GHz covering the GSM 1800/1900, UTMS, Bluetooth, LTE, and WiMAX bands. In addition, the antenna has a good performance with efficiency and peak gain of 82% and 6.3dB respectively. These characteristics allow the antenna to be an attractive candidate for telecommunication systems. Design and analysis of different structures were carried out with Ansys HFSS.

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.

Development of virtual instrument model for parameter estimation of fractal antenna array

AbstractThis paper presents the parameter estimation of the fractal antenna array with the virtual instrument model designed in laboratory virtual instrument engineering workbench software. In this work resonant frequency, gain and voltage standing wave ratio have been used as an output parameter with the change in three input parameters such as radius of a circular patch, height of substrate, and dielectric constant of the material. Measured output parameters have been compared with neural network outputs and error has been represented in a graphical way for each output parameter of the antenna array. Along with output parameter estimation, a designing parameter such as radius of the circular patch has also been estimated with virtual instrument model and absolute error for radius has been shown in the display window of the designed model. The proposed antenna array has been fabricated and simulated results have been validated with measured results.

A wide input power range rectenna for energy harvesting and wireless power transfer applications

This article describes a novel rectifying-antenna design with extended input power range operating at 2.4 GHz for both ambient wireless energy harvesting and wireless power transmission (WPT) systems. The rectenna consists of a 2 × 2 fractal antenna array and a rectifier circuit with a high-power conversion efficiency (PCE) in a wide input power range. This circuit contains two conversion stages based on two different Schottky diodes, and a third stage that dissipates the unconverted input power, which can disturb the harvesting process. These three stages are controlled by a power management block based on circulators, that direct the input power to the adequate stage according to its power range. A prototype of the proposed harvesting system is fabricated and experimentally validated. The measurement results confirm the wide input power range behavior of the designed rectenna with a relatively constant and high PCE (between 58% and 67%) for a power density ranging from 4 to 252 μW/cm2. The proposed solution can be successfully used for both ambient energy harvesting and WPT systems.

Array Pattern Synthesis of Multiband Hexagonal Fractal Antenna Array for Reduced Sidelobe and Deep Null Control using Modified Invasive Weed Optimization Algorithm

Array Pattern Synthesis of Multiband Hexagonal Fractal Antenna Array for Reduced Sidelobe and Deep Null Control using Modified Invasive Weed Optimization Algorithm