This work presents the design, fabrication, and experimental validation of a complete near-field magnetic RFID system tailored for the detection of ultraminiature RFID chipless tags operating in the UHF range. The proposed system comprises four subwavelength-sized chipless RFID tags, a RFID reader and a backend detection system. The chipless tags are implemented as LC resonators consisting of an octagonal loop antenna and a floating capacitor that have areas of 17.89 mm 2 , 2.92 mm 2 , 1.65 mm 2 and 0.75 mm 2 and resonate at 1.21 GHz, 1.33 GHz, 1.29 GHz and 1.18 GHz, respectively. The RFID reader is a frequencyreconfigurable segmented loop antenna with an area of 122.54 mm² that is controlled by voltage and operates between 1.14 GHz and 1.50 GHz. To evaluate the maximum detection distance at which each tag can be detected by the reader, a backend system based on the Frequency Sweep Envelope (FSE) method is applied to the phase derivative of both the reflection coefficient and the input impedance measured at the reader, in absence and presence of the different tags. The results demonstrate that combining the FSE method with the derivative of the input impedance phase provides higher sensitivity to the subtle perturbations introduced by the ultraminiature tags, enabling greater detection distances.