A novel microstrip array antenna based on the meta-material zeroth-order resonator (ZOR) is presented in this paper. Considering both zeroth-order resonance and the array theory, a resonant array antenna has been designed and fabricated which has small dimensions both in length and width as well as an acceptable gain. Since the resonant frequency of the zeroth-order resonator is independent of the physical length of the resonator and determined only by LC values loaded in the resonator, therefore, antenna size can be reduced arbitrarily with no changes in the operation frequency and due to the array structure antenna gain can be enhanced. Additional benefit of the ZOR antennas is lower ohmic losses as compared to the other small antennas and hence the efficiency of the antenna is higher. The discrepancy between simulation and measurement determined by fabricating some of the simulated design and comparison between the results, has been taken into account for designing the final array. A small-sized two-elements ZOR array antenna with 50% reduction in size as compared to the conventional array with a acceptable gain and broad radiation pattern is tested at 4.25 GHz. The proposed antenna has application in radio altimeters. The commercial softwares such as CST and HFSS were utilized for design and analysis of the structure.
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