A Wideband Directive Filter For LO Leakage Reduction in UWB Frequency Domain Chipless RFID Readers

In a vector frequency-domain chipless radio frequency identification (RFID) reader, a wideband mixer down-converts the backscattered signal from frequency-coded tags. The strong leakage signal from the LO port into the IF port of the mixer is a severe limitation of the vector reader. The leakage reduces the dynamic range of the receiver, adversely affecting the reading range. Herein, a wideband directive filter (DF) is designed to absorb the leakage signal, and as a result, improve the reading range of the system dramatically. A prototype filtering scheme is implemented for the stopband region of 4-8 GHz, where a suppression level of 50 dB is achieved.