Multilevel Decoding Scheme for RFID and Sensor Signals in Inductively Coupled Systems

Inhalt:
To enhance the energy efficiency, it is desirable to design inductively coupled RFID or sensor transponder systems with high-Q antenna coils. By increasing the quality factor of the antenna coils the energy efficiency and hence the range for a constant voltage supply of the transponder is improved; however, the bandwidth is decreased by 1 over Q. Thus the reading performance is limited due to a high bit error rate. Our paper presents a new decoding scheme for such highly challenging systems, which improves the data detection significantly and enables the operation of highly energy efficient devices for mobile applications. The principle is based on an advanced maximum-likelihood receiver with a modified matched filter and a soft Viterbi decoding scheme which uses an a-posteriori probability of a Bayes model, which indicates the reliability of the provided data.