Research On Surface Acoustic Wave RFID With Pulse Position And Phase Modulation

Surface Acoustic Wave (SAW) tag is passive and can perform better in harsh environments than other passive Radio Frenquency Identication (RFID) tag.Since it is critical when choosing an efficient modulation method, this paper investigates into the modulation methods of SAW-RFID. The main points have implemented include:Firstly, we discuss the performance of OOK, MPSK, MPPM, TOPPS modulation methods. After the discussion, we come to the conclusion that TOPPS modulation has the highest efficiency. And this conclusion lead us to deeper the research upon TOPPS, and then we face with the temperature drift of time delay and phase in pulse echos.Secondly, we present the architecture of time sampling and frequency sampling tag reader as well as the estimation methods for time delay and phase of pulse echos. And then we give the Cramer-Rao bound respectively.The third and the most important, we analyze the temperature compensation of SAW-RFID. Utilizing the error of phase estimation, we justify that suitable designed time delay can perform temperature compensation. As a result, there comes the new type modulation of TOPPS by using two pulses for temperature compensation.Based on the success of de-modulation with temperature compensation, we propose an improved algorithm called dynamic temperature compensation which can compesate the temperature drift of long time delay. And then we simulate and manufacture tags with TOPPS modulation. After temperature compensation and signal processing, we discuss phase and time delay accuracyFinally, we simply introduce the developed vehicle management system that is basded on SAW RFID technology.