A Comprehensive COMSOL Model for Surface Acoustic Wave RFID

Surface acoustic waves (SAW)s are ultrasonic waves propagating along the surface of solids.SAW RFID tags provide many advantages over the IC-based RFID tags. A comprehensivemodel for simulation of these devices is useful. In previous works, a series of studies have done to analysis this device in frequency domain and the fast Fourier transform and timegatingtechniques are used for data processing. The drawback of the method is long CPUtime. In this paper we propose a simulation model based on finite element analysis and employ proper boundary conditions for RFID SAW tag devices. To save computation time, a 2-D model is proposed. In this model, we calculate the wave propagation velocity and harmonicfrequency to use this data in subsequent step and then a tag with 4 reflectors is simulated. The simulations are done in COMSOL 4.2 and piezoelectric devices module (PZD) isapplied in model. To extend the data capacity of the tags, also the phase modulation is done on the tags, so we required the phase calculation of the Interrogated signal of the tag. In recentstudies very complicated post processing in MATLAB was done to show the phase ofthe Interrogated signal. Finally, we propose a simple and novel post processing method using Electrical circuit (cir) module of the COMSOL, to calculate the phase of the Interrogated signal of the tag.