Abstract

When the length of the antenna is less than a quarter of the wavelength of the operating frequency, good radiation properties are difficult to obtain. However, size limitations can be overcome in this case using a fractal geometry antenna. The shape is repeated in a limited size such that the total length of the antenna is increased to match, for example, half of the wavelength of the corresponding desired frequency. Many fractal geometries, e.g., the tree, Koch, Minkowski, and Hilbert fractals, are available. This chapter describes the details of designing, simulations, and experimental measurements of fractal antennas. Based on dimensional geometry in terms of desired frequency bands, the characteristics of each iteration are studied carefully to improve the process of designing the antennas. In depth, the surface current distribution is investigated and analyzed to enhance the circular polarization radiation and axial ratio bandwidth (ARBW). Both, simulation and experimental, results are discussed and compared. Two types of fractal antennas are proposed. The first proposed fractal antenna has a new structure configured via a five-stage process. The second proposed fractal antenna has a low profile, wherein the configuration of the antenna was based on three iterations.

Highlights

  • Size limitations can be overcome in this case using a fractal geometry antenna

  • Through using a fractal geometry antenna, where the shape is repeated in a limited size, in a way that increases the total length of the antenna to match, for example, half of the wavelength of the corresponding desired frequency, the size limitations can be overcome in this case

  • Fractal geometry is another type of micro strip antenna used in designing antennas

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Summary

Introduction

Fractal means broken or irregularly fragmented and refers to a family of complex shapes that possess an inherent self-similarity in their geometrical structures. The shape is repeated in a limited size such that the total length of the antenna is increased to match, for example, half of the wavelength of the corresponding desired frequency Many fractal geometries, such as tree, Koch, Minkowski, and Hilbert fractals, are used in designing antennas [1]. Through using a fractal geometry antenna, where the shape is repeated in a limited size, in a way that increases the total length of the antenna to match, for example, half of the wavelength of the corresponding desired frequency, the size limitations can be overcome in this case Many fractal geometries such as the tree, Koch, Minkowski, and Hilbert fractals are used in designing this type of antenna. Minkowski Fractal [6], Koch Fractal [7], H-Fractal [8], Sierpinski gasket arrangement [9], Fern Fractal leaf [10], Mandelbrot Fractal antenna [11], Amer fractal slot [12], Sunflower Fractal [13], Flame Fractal [14] and Butterfly Structure [15]

Compact fractal antenna
Resonant frequencies
Effect of the ground size
Measurements and results The five iterations are fabricated as shown in Figure 12
Meandered ring fractal antenna
Antenna design
Current distribution
Circular polarization
Findings
Conclusion
Full Text
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