A software-defined radio RFID reader design with improved wireless power transfer capabilities

We present a SDR-based RFID reader design possessing two features that allow to improve the wireless power transfer capability and thereby extend the reading range of passive transponders: 1) The reader generates optimized non-CW powering waveforms that improve the RF-DC conversion efficiency of passive transponders. The sensitivity of an RFID chip was measured using a CW and several non-CW signals, and a sensitivity gain of more than 3 dB relative to the CW was obtained for a 9-tone multi-sine signal. 2) Moreover, the reader employs a multi-polarization antenna scheme that switches between several linear polarizations to deliver 3 dB more power compared to circular polarization, while maintaining the desired orientation insensitivity.