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A braod bandwidth and high gain rectangular patch antenna was specifically designed in this paper using planar-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed strip-line gaps etched on the metal patch and ground plane, respectively. Demonstrated to have left-handed characteristics, the patterned metal patch and finite ground plane form a coupled capacitive-inductive circuit of negative index metamaterial. It is shown to have great impact on the antenna performance enhancement in terms of the bandwidth significantly broadened from a few hundred MHz to a few GHz, and also in terms of high efficiency, low loss and low voltage standing wave ratio. Experimental data show a reasonably good agreement between the simulation and measured results. This antenna has strong radiation in the horizontal direction for some specifical applications within the entire band. 1,2 represents one of the most commonly utilized printed antennas in practice. It enjoys its advantages of low profile, simple structure, low cost, and omnidirectional radiation patterns 1,2 . A narrow bandwidth is, however, the main drawback of the microstrip patch antennas. Some approaches have been therefore developed for bandwidth enhancement 3-6 . Among those common ones, one is to increase the height of the dielectric substrate while the other is to decrease the substrate dielectric constant. Certainly, the latter will induce the matching circuits to be impractical due to excessively wide lines designed.Since the artificial left-handed materials (LHMs) or metamaterials were proposed, theoretically characterized, and experimentally realized 7-13 , scientists and engineers have tried various ways to bring these special material characteristics into practical applications. The metamaterials have been successfully applied in optical frequency band for optical imaging [14][15][16][17] . Although it is easier to realize metamaterials in microwave frequency region for negative refractions, there was still little progress toward practical applications 18 . At microwave frequencies, potential applications include primarily (a) substrate materials for antenna and microwave component designs and fabrications, and (b) absorbing materials for engineering and radar applications. For example, split ring resonators (SRRs) 11,[19][20][21] and some other planar structures 22-24 were applied in some antenna fabrications to minimize the size and enhance the radiation. Also in some other designs, artificial magnetic materials 10,25 with

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