A Semi-Passive CDMA-Based RFID Transponder Platform for the UHF Band

Inhalt:
This paper presents the concept and realization of a semi-passive UHF RFID transponder platform, featuring a direct sequence code division multiple access (DS-CDMA) channel access method for the RFID uplink. The UHF RFID system as a whole comprises several transponders and a CDMA-capable RFID reader. By means of CDMA as anti-collision protocol every transponder may transmit data at the same time within the same frequency band. In addition, the transponder platform provides some limited downlink abilities, including carrier frequency and field strength measurement. The paper shows experimental results of the proposed transponder platform including measurements of simultaneous data transmission based on backscattering. Furthermore, some basic distance measurements were carried out.