Proximity-Coupled Microstrip Patch Antenna Miniaturization Using New Fractal Geometry S. Sadat*, M. Fardis, Gh. Dadashzadeh, R. K. Baee Iran Telecommunication Research Centre ssadat@itrc.ac.ir Abstract In this paper, for more antenna miniaturization, we present a novel fractal geometry that allows decrease in the resonance frequency without occupying more space, while remaining radiation pattern similar to that of normal square patch. Also for improving the inherently narrow bandwidth of patch fractal antenna a proximity-coupled feed is implemented. The performance is demonstrated by simulation based on a numerical analysis with the Finite Element Method (FEM) and a practical application to Personal Communication Services (PCS). Keywords: Fractal, Microstrip Antenna, Bandwidth, 3/2 Curve. Introduction When the size of an antenna is made much smaller than the operating wavelength, it becomes highly inefficient. Its radiation resistance decreases, while proportionally, the reactive energy stored in antenna neighborhood rapidly increases. Both phenomena make small antennas difficult to match to the feeding circuit, and they display a high Q with very narrow bandwidth when it’s matched [1]. There are various solutions to overcome this problem. The best way making small antenna is application of fractal geometry [2], [3]. In recent years, the fractal shape antenna elements have drawn interests of many antenna designers. Fractal geometries are featuring two common properties: fractals are space-filling contours, meaning electrical lengths play such as a viable miniaturization technique and self similarity property. Fractal shaped antenna have various advantages, such as wideband, multiband and reduced size in wire antennas [2], [3], but in microstip patch antennas the gain and impedance bandwidth decreases seriously, so we should solve this problem using the methods of broadbanding of a patch antenna. For improving the inherently narrow bandwidth of a microstrip antenna, it is very effective to use an electrically thick substrate [4]. Several studies for feeding the microstrip antenna with a thick substrate have been reported, such as the L-shaped probe [5] and the capacitively probe-fed structure [6]. Recently the proximity-coupled microstrip antenna with a linear slot in ground plane has also been proposed [6], [7]. It should be noted that the proximity-coupled microstrip antenna without a slot in the ground plane is hard to achieve impedance matching. In this paper, we miniaturize a microstrip patch antenna with suitable gain and impedance bandwidth. For increasing the frequency bandwidth, a proximity-coupled feed is used and an H-shaped slot is placed in along the diameter of the square patch. In order to validate, we compare the proposed model with Minkowski and koch geometries. Proposed Geometry Description The proposed model is an iterative model to a normal square patch with a generator of shape is called 3/2 curve, shown in fig. 1; substituting both length and width of the patch antenna structure with generator shape. Fig. 1 Generator for 3/2 curve fractal 0-7803-8883-6/05/$20.00 ©2005 IEEE