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In this letter, circularly polarized (CP) chipless tags for a ultrawideband radio-frequency identification (UWB-RFID) system are demonstrated for the first time. Different from conventional linearly polarized tags, CP tags not only help to significantly reduce the mutual coupling between the transmitting and receiving antennas in a UWB-RFID reader, but also greatly lessen the signal ratio between structural and antenna modes to improve system performance. In addition, short delay line is adopted to make the chipless CP tag with compact size. Nevertheless, a short delay line usually results in the structural and antenna modes being overlapped. To separate these signals, a time-domain processing scheme is then proposed and validated. Measured results and system demonstration show that the compact chipless CP tag is a very promising candidate for low-cost UWB-RFID applications.