A Study of Software Defined Radio Receivers for Passive RFID Systems

In this paper, a Software Defined Radio (SDR) receiver structure suitable for readers using passive Radio Frequency IDentification (RFID) is presented. In such a passive RFID configuration, the undesirable DC-offset phenomenon may appear in the baseband of the reader receiver. This phenomenon can severely degrade the performance of the extraction of valid information from a received signal in the reader receiver. To mitigate this DC-offset phenomenon, a software receiver structure is proposed to remove the DC-offset in the digital domain. This aim can be e.g. achieved by using three methods: 1) Removing the DC offset using a Hamming windowing FIR high pass filter. 2) Extracting useful transition information from the corrupted signal using an edge detector. 3) Using a first order Butterworth IIR notch filter to remove the unwanted DC offset. A comparison between these methods based on measurements is presented to analyze the advantages and disadvantages of the different approaches.