This paper presents a 7.5 × 7.5 mm 2 tunable segmented square loop reader antenna working in UHF band for magnetic near field RFID applications. The proposed reader is combined with a post-processing method based on frequency sweep envelope (FSE) for detecting miniaturized chipless tags. Using FSE method, the reader can detect octagonal single turn loop resonators of 17.89 mm 2 , 2.92 mm 2 , 1.65 mm 2 and 0.75 mm 2 dimensions at 19.5 mm, 10 mm, 6.5 mm and 1 mm distances, respectively. These results improve the ones obtained with others chipless systems based on phase-dip, reflection distortion (PRD), group delay distortion (GDD) and splitting frequency (SF) detection methods. Moreover, the designed chipless system is capable of reaching detection ranges comparable to chipped systems with similar dimensions. In view of the promising results obtained with the proposed system, some possible modifications for improving the detection range are suggested.