A Bidirectional Semi-Passive DS-CDMA-RFID Transponder for the UHF Band
This paper presents a first realization of a semi-passive UHF RFID transponder featuring a direct sequence code division multiple access channel access method for the RFID up-link, and, in addition, some limited down-link abilities, including carrier frequency and field strength measurements. The paper shows experimental results of the proposed transponder, which is already included within an UHF RFID system, containing an RFID reader being able to read out the transponders' data. The focus of this paper is on the transponder's modulator, generating an ASK-like modulation scheme by impedance miss-matching techniques. This paper presents results obtained from real life measurements of a realized UHF RFID transponder qualified for the application in CDMA-based RFID systems.