Frequency-domain chipless RFID readers hold tremendous promise as a low-cost solution for mass production of this technology. However, the strong self-jamming signal leakage, from the transmitter to the receiver, significantly degrades the sensitivity of the reader. As a result, the maximum reading range of the system is diminished. To address this issue, we studied the sources of interference signals in the system and proposed a method to significantly reduce them. An ultrawideband compensator, over the wide frequency range of 4.3 to 7.3 GHz, was designed and implemented. This method realized an interference isolation better than 40, 55, and 55 dB in single-antenna, dual-polarized antenna, and two-antenna readers, respectively. A noticeable 25-dB excessive isolation to that of the conventional architecture which should help to bring this technology closer to commercial adoption.