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.
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