Anti-collision technique of SAW ID tags at unknown temperature using integer programming

Based on a synchronous separation method, a new identification algorithm for separating multiple asynchronous surface acoustic wave identification tags at variable unknown temperature is presented. For identification of the codes, the estimation of the reflector delays (round-trip delay-times - RTDTs) is necessary. Reading out multiple tags simultaneously, these impulse response patterns superpose and the assignment between reflectors and tags is lost. Furthermore, the answer and as a consequence, the RTDTs of the tags are scaled, thus stretched or compressed due to external effects, e.g., temperature. The radial tag position results in a shift of the impulse response and is handled as an offset. These parameters are usually unknown. In this paper, a novel technique is introduced, which estimates the offsets, scalings, and codes.