Model-Based Identification Method for Pulse Position Coded Surface Acoustic Wave Identification Tags

In this paper, a novel code identification algorithm based on a least squares reflector grid estimation technique for single delay-line-based surface acoustic wave (SAW) sensor identification tags using pulse position coding is derived. The least squares estimation procedure considers all round-trip delay time information encoded on a single tag. Hence, the pulse position coding grid can be estimated with higher accuracy compared with the standard grid estimation technique, which uses only framing reflectors for grid calculation. The need for framing reflectors is completely eliminated, and thus additional space for data on the tag is obtained. With a more accurate grid, the probability of correct identification increases. Ensuring a large data capacity on the SAW tag, the newly derived estimator also works well with fine pulse position coding grids, for which common grid estimators fail, in particular, in low signal-to-noise ratio scenarios.