Ademola O. Kaka

Modified Hilbert fractal geometry, multi‐service, miniaturized patch antenna for UWB wireless communication

Purpose – The purpose of this paper is to describe a modified Hilbert‐based fractal antenna for ultra wideband (UWB) wireless applications. Simulation results show excellent multi‐band characteristics for UWB wireless applications.Design/methodology/approach – A Hilbert curve‐based fractal is optimised for self‐replicating, space‐filling and self‐avoiding properties. In the proposed design, the Hilbert curve is applied to a rectangle as an initial iteration and maintained for the later iterations. Additionally, a Yagi‐like strip is removed from the second iteration of the Hilbert patch and a hexagonal portion is removed from the substrate to achieve good optimization. The antenna feed is created through a micro‐strip line with a feeding section. Finally, a partial ground plane technique is used for improved impedance matching characteristics. A finite element method (FEM) is used to simulate the modified Hilbert model with commercially available Ansoft HFSS software.Findings – The proposed antenna is mini...

A fractal geometry, multi-band, miniaturized monopole antenna design for UWB wireless applications

A new combined fractal geometry based Monopole antenna design for ultra wideband (UWB) applications is presented in this paper. This fractal structure is implemented on square and Minkowski fractal is applied to the lines of a square. Then, a Sierpinski carpet fractal is formed on the first iteration of the Minkowski fractal. The proposed antenna is miniaturized (45 mm × 45 mm) and has multi-band characteristics. Simulation results show that the presented antenna has a reflection coefficient characteristic < −15dB, 80% radiation efficiency, 4–6dBi antenna gain and omni-directional radiation pattern properties over the UWB bandwidth (3.1 – 10.6 GHz). The gain variation is due to increased directivity at higher frequencies.

Dual band implant antenna design with miniaturized and biocompatible characteristics for wireless health monitoring

In this paper, the combination of Hilbert fractal geometry and the serpentine shape based microstrip implant antenna design proposed and optimized for wireless medical applications. The proposed antenna is miniaturized 5.5 × 5.8 × 1.7 (width × height × thickness mm3) and operates for dual band (MICS 402-405 MHz ile ISM 2.4-2.48GHz) operations. Superstrate is applied on top of the antenna to avoid a direct contact with the metallization and achieve biocompatibility. Implant antenna is simulated in three layer tissue (skin, fat and muscle) model. Simulation results show that the presented antenna has a reflection coefficient characteristic better than -10dB, omni-directional radiation pattern and acceptable specific absorption rate values for human body.

Design of a low-loss and multi-band fractal-based antenna for ultra wide band communication

As the demand for high bandwidth applications is increasing for wireless communication, the need for wideband antennas increases as well. In this paper, a new small fractal antenna design concept is proposed for ultra wideband (UWB) applications. UWB is a technology that high data rates (480Mb/s) and high bandwidth (0.528 – 7.5 GHz) with good signalling characteristics for wireless personal area networks (WPAN). First band group (BG:1, 3.1 – 4.752 GHz) of the UWB band is simulated and −41.3 dBm/MHz is observed. Fractal antenna geometry shows self-similarity characteristics that operates at multiple wavelengths with similar radiation patterns. Therefore, it is suitable to use for multi band orthagonal frequency division multiplexing (MB-OFDM) based UWB applications. Proposed fractal antenna design is analysed with less than −20dB return loss (S11) over whole UWB bandwidth (3.1 – 10.6 GHz). In addition to this, omni directional radiation pattern is observed for the BG:1 of the UWB band.

Design of miniaturized and biocompatible implant antenna for retinal prosthesis systems

In this paper, the combination of Hilbert fractal geometry and rectangular shape based microstrip implant antenna design for retinal prosthesis systems is presented. The proposed antenna is miniaturized 5.8 × 6.5 × 2 mm3 (width × height × thickness mm3) and operates in the ISM band (2.4-2.48 GHz). PDMS superstrate is applied on top of the antenna to avoid a direct contact with the metallization and achieve biocompatibility. Implant antenna is simulated at the size of the eyeball (12.5 mm) which is filled with vitreous humor liquid model. Simulation results show that the presented antenna has a reflection coefficient characteristic <; -15dB and axial ratio of 1.08 dB for circular polarization. Designed antenna has acceptable specific absorption rate values for eye implantation at 2.4 GHz.

Design of miniaturized and biocompatible antenna for continuous health monitoring

In this paper, the combination of Hilbert fractal geometry and the serpentine shape based microstrip implant antenna design for health monitoring is presented. This structure is implemented on an empty triangle. First, three copies of the first Hilbert fractal geometry is applied on the top edge of the triangle. Then, a serpentine shape is applied to the main body of the triangle in order to increase the electrical length. The proposed antenna is miniaturized 10 × 8.4 × 2.6 mm3 (width × height × thickness mm3) and operates in the MICS band (402-405 MHz). Superstrate is applied on top of the antenna to avoid a direct contact with the metallization and achieve biocompatibility. Implant antenna is simulated in three layer tissue (skin, fat and muscle) model. Simulation results show that the presented antenna has a reflection coefficient characteristic <; -19 dB, 80% radiation efficiency and omnidirectional radiation pattern properties over the MICS bandwidth.

Miniarutized and lightweight automotive antenna design for vehicle to vehicle communication

In this paper, automotive antenna design for vehicle to vehicle communication is proposed. Antenna design is based on elliptical geometry by utilizing the self-similarity of the fractal concepts. The initiator is an elliptical shape based vertical to horizontal ratio of about 3:1. The proposed antenna is a combination of two reproduced elliptical shape placed at +/- 30 degrees to the central point of the initiator. Antenna is miniaturized (42 × 34 mm2) and lightweight with efficient characteristics. Simulation results show that the presented antenna has a reflection coefficient characteristic better than -17.5 dB, 70% radiation efficiency, 4-6dBi antenna gain and omni-directional radiation pattern properties over the 75 MHz of 802.11p standard (5.85 - 5.925 GHz).

Miniaturized stacked implant antenna design at ISM band with biocompatible characteristics

Purpose – A vertically stacked, three layer hybrid Hilbert fractal geometry and serpentine radiator-based patch antenna is proposed and characterized for medical implant applications at the Industrial, Scientific and Medical band (2.4-2.48 GHz). Antenna parameters are optimised to achieve miniaturized, biocompatible and stable transmission characteristics. The paper aims to discuss these issues. Design/methodology/approach – Human tissue effects on the antenna electrical characteristics were simulated with a three-layer (skin, fat and muscle) human tissue model with the dimensions of 180×70×60 mm3 (width×height×thickness mm3). Different stacked substrates are utilized for the satisfactory characteristics. Two identical radiating patches are printed on Roger 3,010 (e r=10.2) and Alumina (e r=9.4) substrate materials, respectively. In addition, various superstrate materials are considered and simulated to prevent short circuit the antenna while having a direct contact with the metallization, and achieve bio...

Multi-band and miniaturized antenna design for ultra wide band applications with band rejection characteristic

In this paper, the combination of concentric square loop and the Koch curve fractal geometries based microstrip antenna design for ultra wideband (UWB) applications is presented. This fractal structure is implemented on a empty square. Three progressively concentric square loop is applied inside the empty square and a full square is applied to the center for the first iteration. Then, a Koch curve fractal is applied to the lines of the first iteration. The proposed antenna is miniaturized (44 × 43 mm2) and has multi-band characteristics. Simulation results show that the presented antenna has a reflection coefficient characteristic <; -15dB, 80% radiation efficiency, 4-6dBi antenna gain and omni-directional radiation pattern properties over the full UWB bandwidth (3.1 - 10.6 GHz) while showing the band-rejection performance in the frequency band of 4.75-6.75 GHz.