Phase difference of arrival distance estimation for RFID tags in frequency domain

The paper gives an overview of phase based ranging techniques, focusing on the phase difference of arrival method measured in frequency domain (FD-PDoA). After a theoretical overview of distance estimation and localization, it introduces an experimental RFID front-end prototype used for FD-PDoA measurements. Proposed modular design is very flexible and allows easy replacement of any block, as well as direct access to all required low-level signals. The main part of the article is devoted to range estimation experiments in an anechoic chamber, using the developed front-end and signal processing in a PC with MATLAB. Several measurement problems are addressed, such as demodulator phase imbalance correction, wrapped phase recovery, etc. Ranging is performed with common passive EPC Gen2 RFID tags.