Radiation properties of fractal microstrip antennas

Abstract

SUMMARYThe fundamental configuration method and radiation characteristics are described for a new type of multiband planar antenna in which triangular microstrip antennas (MSA) with a Sierpinski fractal structure are used as the radiating elements. In order to verify the performance of the present antenna system, Sierpinski triangular microstrip antennas with multiband characteristics are fabricated for trial in the C band and X band. According to the experiment, excellent multiband characteristics can be obtained with the proposed antennas. The measured radiation patterns agree very well with those obtained by numerical calculations. Hence, it is clear that the present antenna system can be a promising format for a multiband planar antenna with a low profile.

Radiation properties of modified fractal microstrip antennas

“…3 are realized. When a coaxial feed scheme [3] attaching the feeding coaxial connector directly to the radiating element rather than employing this L-probe was used, it was not possible to achieve a return loss of less than -10 dB at all modes in the test antenna with the dimensions shown in Fig. 1.…”

“…Also, when multiband operations are realized by using a conventional equilateral triangular MSA with a nonfractal structure [17], a unidirectional pattern is obtained in the main mode, as is well known. In the first and second higher-order modes, the patterns have two or three lobes so that it is difficult to realize a unidirectional pattern [3]. In the present research, the targeted characteristics are such that the return loss at each resonant frequency f r in the multiband characteristic is less than -10 dB and the radiation pattern at each f r is unidirectional, while the cross-polarization level in the boresight direction is less than -20 dB.…”

“…The eigenmodes are called the 1st, 2nd, 3rd, and 4th modes in order of increasing resonant frequency f r . The main objectives of the present research are as follows: 1 to attain multiband operation of an antenna by generating several eigenmodes exhibiting unidirectional radiation patterns by utilizing the effect of slit loaded elements, in order to realize an antenna system whose design capability is superior to the conventional antenna systems intended to achieve unidirectional radiation properties of higher-order modes [3]; 2 by changing the slit shape of the loading slits, to control the value of f r at each mode so that an antenna system exhibiting multiband characteristics at the desired frequencies is realized. In the present research, the SG-MSA with slits is chosen for study.…”

“…2 A metallic shorting pin is inserted at an appropriate location of an SG-MSA element [2] or the element structure of the SG-MSA element is deformed [7] to realize multiband characteristics. 3 An equilateral triangular MSA element is loaded inside an SG-MSA and multiband characteristics are realized with a single point feed [3,11,13]. However, in these antenna systems, it is not easy to realize a unidirectional radiation pattern in all frequency regions exhibiting multiband characteristics.…”

“…Recently, in line with the broadband and multiband trends of wireless communication devices, research on fractal antennas has been carried out extensively, since this type of antenna is considered to exhibit multiband characteristics [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, the fractal structure of the Sierpinski Gasket type studied in this paper has been used mainly in the radiating elements of monopole antennas for multiband applications [5,6,8,10,14].…”