Interference recognition and fault reduction method for FSCW-based SAW-tag readers

Many state-of-the art surface acoustic wave (SAW) sensor applications operate in the 2.45GHz industrial-scientific-medical band utilizing radar based reader units. In particular, focusing on identification tag applications, the large available bandwidth in this frequency band offers the possibility to realize a large number of different codes on the SAW tag. Unfortunately, numerous other appliances operating at the same frequency range-especially WLAN devices-may introduce strong interference to the sensitive SAW sensor readout. In this paper we present a simple method suitable for frequency-stepped continuous-wave radar based reader systems to recognize these interferences online during interrogation, to lower the code error rate and avoid a time-consuming re-interrogation process. The performance of this method is verified by measurements.