proposed antenna, probe feeding and an air gap (capacitive gap) were used. Simulations were conducted to optimize the lengths of the probe and air gap in order to obtain the widest bandwidth in terms of return loss (VSWR [lt] 2) at 2 GHz band. According to the measured results for the antenna implemented, the impedance bandwidth was 734 MHz (29.01%) ranging from 2.163 to 2.897 GHz and the axial ratio bandwidth (AR [lt] 3dB) was 135 MHz (5.48%) ranging from 2.394 to 2.529 GHz. The CP characteristic of the antenna can be applied to mobile applications for the 2.4 GHz WLAN. [3][4][5][6][7][8][9][10][11][12][13][14]. Generally, the properties of the fractal geometry are related with the electromagnetic behavior of the antennas. As for the Koch fractal dipole antenna, if the heights of the antennas are fixed and the number of iterations is increased the resonant frequency of the antennas decreases. Decreasing the resonant frequency with fixed height has the same effect as miniaturizing the antenna at a fixed resonant frequency. In addition to the miniaturization effect, using fractals improves the antenna parameters, making them suitable for many applications. Most of the fractal antennas can also be used as multiband and wideband antennas because of the self-similar property of the geometry. Sierpinski antenna is one of those which can be used to achieve similar radiation patterns at various operating frequency bands.When small and multiband antennas are considered, fractal trees are also very good candidates [15,16]. They are widely used in the design of miniaturized antennas because of their space filling ability, compact size, and multiband behavior. Three dimensional fractal trees with self-similar branch structure are also examined in [17,18]. Fractal tree antennas are designed by using various scale factors [19] but the length ratios of consecutive branches are constant. In this study, the antennas with nonuniform branch length ratios are proposed and investigated. The new antennas are compared with the ones designed by using uniform length ratios in terms of the fundamental antenna parameters. The antennas are also fabricated and measured. ANTENNA DESIGNFractal tree antennas generated by applying an iterative procedure are obtained by using a constant scale factor and this factor in the designs is generally chosen as 1/2. Therefore, the branch lengths increases according to the number sequence 1, 2, 4, 8, 16, 32, . . . from the tip of the antenna to its base. Since the length of the following branch is the double of the previous one, the antenna is called as the D version in this work. The new antenna whose branch length ratios are not constant is designed similar to the D version but its branch lengths increases according to the Fibonacci number sequence from the tip to the base. The Fibonacci numbers appear in many unexpected places in nature such as on flowers, plants, and trees [20]. Therefore, in this study, it is intended to use this special sequence for the generation of fractal trees. The Fibonacci...
-In this paper, a compact monopole microstrip antenna is presented for dual-band WLAN mobile modules operating in 2.4 GHz and 5.2GHz bands. A novel dual-broadband multiple-input-multiple-output (MIMO) antenna Set Top Box (STB) system is developed. The bandwidths (return loss 10 dB) achieved for the dual-band antenna element are 2.4 GHz (20%) for the lower band and 5.2 GHz (38%) for the upper band. Various configurations of this monopole antenna for MIMO application are also studied. It is shown that good MIMO performance can be achieved even for small element spacing. Simulation results are compared and discussed. Promising small-size WLAN monopole antenna suitable to be mounted along the front edge of the STB with metal housing is presented. The antenna is formed by a two branch structure of a monopole strip and a loop strip. The antenna has attractive features of low profile and wideband operation.
Abstract-Sinc functions are used in the basis and testing procedures in the conventional method of moments (MoM) formulation. But unlike conventional MoM, simple pointwise meshing is enough and no integral computation is required due to the mathematical properties of the sinc function. The simulation results of surface current densities and radar cross section for a few wavelength square flat plate are obtained by using our own codes. The results are compared with those of the rooftop basis functions. The CPU-time decreases by half of the time of the conventional method. The error that occurs from the approximated integral of the sinc function in the computation of main matrix elements is very small and decreases while the bandwidth of the sinc function increases.
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