This paper presents a new miniature low cost planar RFID antenna designed @ 2.45 GHz. In order to validate the final structure, we have conducted a study on two antenna structures. The first one is based on a rectangular patch with a centred slot line, and the second one is based on a monopole antenna. By comparing the performances of both structures we have chosen the second one because due to the fact that presents a miniature dimensions and especially due to their compactness and robustness against the mechanical tolerances. The antenna achieved and measured demonstrates a good agreement between simulation and measurement results. Moreover, for improving the matching input impedance of the antenna, we have studied and optimized all geometry dimensions of the whole structure. For the feed line we have used a CPW feed which permits to integrate this antenna easily with the memory circuit to form a tag system.