A new UHF/ultra wideband-radio frequency identification system to solve coexistence issues of ultra wideband-radio frequency identification and other in-band narrowband systems

This paper presents a new Ultra Wideband-Radio Frequency Identification (UWB-RFID) transceiver to mitigate the coexistence issues of RFID systems and IEEE802.11.a WLAN or other narrowband (NB) systems. The UWB pulse used in the RFID tag is a frequency up-conversion of the Gaussian pulse first derivative, which has a null in the frequency spectrum. The null is adjusted to be at the center frequency of the WLAN signal, mitigating the mutual interference between RFID and NB systems. In the receiving state, the proposed RFID reader operates in five modes: interference detection, transmitter frequency adjustment by sending commands to the tag, time-window synchronization, phase and frequency locking, and data reception. During the interference detection mode, the reader serves as a superheterodyne receiver, while it works as an envelope and matched-filter receiver in the synchronization and locking modes, respectively. In this paper, we show analytically that the reader's frequency in a Phase-Locked Loop (PLL) can lock on the null frequency of the transmitted signal by the tag. Furthermore, the reader's performance with particular emphasis on PLL and synchronization in the presence of a strong NB interferer is also evaluated. Simulation results demonstrate that the frame synchronization and the phase and frequency lock of the proposed UWB-RFID transceiver are possible.