This paper presents a reading methodology for RFID readers to overcome the problem of the limited reading range and enhance the reading efficiency of the UWB chipless tags in a noisy environment. We apply this methodology on passive UWB chipless tag consists of a circular patch loaded with multiple rings resonators. The main problem of these passive chipless tags is that the reflected UWB power is hardly detected, because the transmitted UWB power is dramatically low by the FCC regulations. In this work, is a new methodology has been developed to make the best use of the restricted UWB regulations to increase the effective radiated power by the RFID reader. This leads to a significant improvement of the reader range and the overall system performance. The FCC regulation states that the maximum allowed limit for the Effective Isotropic Radiated Power (EIRP) for an UWB device operating in the 3.1-10.6 GHz must not exceed than -41.3 dBm/MHz. However, the FCC regulations allows a peak level of emission with a maximum of 0 dBm, contained within a bandwidth of 50 MHz centered at the frequency at which the highest emission occurs. Therefore, the methodology depends on detecting the presence of a tag in a carrier sense manner using frequency sweeping and hoping techniques, instead of sending an UWB signal. The link budget analysis shows a considerable enhancement in the RFID system range and improving the signal to noise ratio at the reader. Simulation results show the expected improvement of the overall system performance.
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