Koch Fractal Slot Research Articles

Multiband PIFA antenna with Koch Fractal slot for GPS, LTE and WiMAX wireless communication systems

In this article, a five frequency band PIFA antenna for GPS (1.57 GHz), LTE (2.6 GHz) and WiMAX (3.17GHz, 4.1GHz, 4.83GHz) applications is presented. The proposed antenna consists of a PIFA antenna with a Koch fractal slot at the first iteration that was applied to all sides of a square located in the center of the radiating element. The radiating patch modification of the proposed antenna with the fractal slot made the antenna multiband and also contributed to miniaturize the proposed antenna compared to the initial form. The results presented in this work are carried out under the CST MWs software and compared to those obtained by the HFSS software where a good agreement was recorded. The proposed antenna has a gain ranging from 1.13dB to 6.01dB corresponding to the five frequency bands achieved.

A Second-Iteration Square Koch Fractal Slot Antenna for UHF Downlink Telemetry Applications in CubeSat Small Satellites

This article presents the design, fabrication, and measurement of a square Koch fractal slot antenna for UHF band using both the FR4-G10 and Cuclad 250 substrates. Conveniently, this 56.56 cm full-length antenna possesses a geometry that allows it to be incorporated into the standardized 10 cm × 10 cm faces of the CubeSats. Furthermore, it is shown that both selected substrates exhibit an acceptable performance at the frequency of interest despite the economic cost difference and relative permittivity. Hence, the commercial FR4-G10 antenna substrate can be preferred because of its low-cost and admissible performance at 458 MHz, which is a frequency in the UHF band that is commonly used for telemetry, tracking, and command downlinks of CubeSats. Measurements show that the proposed antenna exhibits a reflection coefficient of −16.53 dB, a bandwidth of 22.62 MHz at −10 dB, a VSWR of 1.3508, a normalized impedance of 0.794 − j0.173 at 50 Ω, and a directivity of 2.24 dBi. The contribution of this work consists in the use of a fractal geometry to construct a low-cost slot antenna working at UHF frequencies over the limited area of the CubeSat faces and in order to optimize the area for an eventual coexistence with solar cells.

Multiple fractal-shaped slots-based UWB antenna with triple-band notch functionality

A planar elliptical shape band-notched UWB antenna with multiple fractal-shaped slots and a Sierpinski fractal curve-shaped ring resonator at the back of the substrate is introduced in this paper. The proposed antenna exhibits a triple-band notch characteristic. Koch fractal slot etched from the radiator is responsible for creating notched band centred at 5.5 GHz for wireless local area network rejection. The Minkowski fractal slots in the ground planes create rejection characteristics at 8.1 GHz to avoid interference with X-band uplink satellite communication systems. The RFID rejection band centred at 6.8 GHz is achieved by using a Sierpinski fractal curve-shaped ring resonator at the back of the substrate. Sierpinski fractal slot of third iteration on the radiator contributes to an impedance bandwidth of 2.8–12 GHz with VSWR < 2 by improving matching at lower frequencies except at three notched bands. The antenna gain varies from 1.5 to 4 dBi over the band. Stable radiation patterns are obtained throughout its operating frequency. The antenna has a compact size of 41 mm × 45 mm.

CPW-Fed Fractal Slot Antenna for UWB Application

A novel printed ultrawideband (UWB) CPW-fed Koch fractal slot antenna is proposed. The UWB bandwidth is largely enhanced by the three-iteration Koch fractal slot whose extrusive angle is 900 instead of 600 to obtain better convoluted shape and self-similarity. The −10 dB impedance bandwidth is 3400 MHz (1270–4670 MHz) or about 114% in comparison with 1290 MHz (1620–2910 MHz) or about 57% of the referenced square slot antenna. Details of the proposed antenna design and performance are presented and discussed.

Ultra-Wideband Koch Fractal Antenna with Low Backscattering Cross Section

In order to find an effective way to reduce the radar cross section (RCS), the influence of different metal areas of the square slot antenna on the RCS is analyzed. Koch fractal slot and rectangular loop feed-in patch are applied to reduce the RCS. An ultra-wideband Koch fractal slot antenna with low backscattering radar cross section is achieved. In comparison with the initial square slot antenna, the antenna has lower backscattering cross section and more stable gain almost in the whole operating frequency band. The radiation patterns are comparatively symmetrical at both 3 GHz and 8 GHz. Simulated and measured results also show that the –10 dB impedance bandwidth is from 2.7 GHz to more than 15 GHz while that of the square slot antenna is only from 3.0 GHz to 13.1 GHz.

Miniaturized Dual-Mode Filter Using Fractal Slot and Snaky-Shape Spur-Line

In this paper, miniaturized dual-mode filters using Koch fractal slot and snaky-shape spur-line are proposed. Compared to conventional dual-mode bandpass filter (BPF), fractal slot and snaky-shape spur-line provides more current distribution distortions which improve the electrical length and realize a compact design. A size reduction of about 61.1% is obtained compared to the traditional design. In addition, the relative 3-dB bandwidth is improved by about 20.7% after adopting the second-order Koch fractal shape. This dual-mode BPF has a good prospect in compact and broad-band microstrip circuit applications.

CPW-Fed Koch Fractal Slot Antenna for WLAN/WiMAX Applications

A dual wide-band CPW-fed modified Koch fractal printed slot antenna, suitable for WLAN and WiMAX operations, is proposed in this paper. Here, the operating frequency of a triangular slot antenna is lowered by the Koch iteration technique resulting in a compact antenna. Studies on the impedance and radiation characteristics of the proposed antenna indicate that a modified Koch fractal slot antenna has an impedance bandwidth from 2.38 to 3.95 GHz and 4.95-6.05 GHz covering 2.4/5.2/5.8 GHz WLAN bands and the 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Empirical relations are deduced and compared with the results.

Compact frequency notched ultra-wideband fractal printed slot antenna

A novel frequency notched ultra-wideband (UWB) fractal printed slot antenna is proposed. The antenna is similar in configuration to a conventional microstrip-fed wide slot antenna, however, by introducing a Koch fractal slot, not only the size of the antenna is reduced significantly but also frequency notched function is achieved. Several properties of the antenna such as impedance bandwidth, frequency notched characteristics, radiation patterns and gain, have been investigated numerically and experimentally in detail. As will be seen, the operation bandwidth of the antenna is from 2.85 to 12GHz, in which a frequency notched band from 4.65 to 6.40GHz may be achieved, and relatively stable, omnidirectional radiation performance over the entire frequency range has also been obtained.

A slow‐wave structure with Koch fractal slot loops

AbstractIn this Letter, a Koch slot loop in the ground plane has been utilized to obtain slow‐wave characteristics, and its electrical performances are analyzed with the use of the ABCD matrix approach. The validity of this approach has been verified through experimental results, and this technique was then applied to microstrip patch antennas in order to obtain a small antenna size. The cross‐sectional areas of this type of antenna are 47% to 65% smaller than those of conventional square patches. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 87–88, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10381