Accurate Indoor Ranging by Broadband Harmonic Generation in Passive NLTL Backscatter Tags

• Published in: IEEE transactions on microwave theory and techniques Vol. 62; no. 5; pp. 1249 - 1261
• Main Authors: Yunfei Ma, Kan, Edwin Chihchuan
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2014; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Ambiguity; Applied sciences; Backscatter; Broadband; Broadband communication; Circuit properties; Design. Technologies. Operation analysis. Testing; Distance measurement; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Frequency conversion; Harmonic analysis; harmonic generation; Harmonic generations; Harmonics; Indoor; indoor communication; Integrated circuits; Interference; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Phase error; phase measurement; Radiofrequency identification; Radiolocalization and radionavigation; ranging; Reflection; RF identification (RFID) tags; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Tags; Telecommunications; Telecommunications and information theory; Phase measurement; Backscattering; Continuous wave; Accuracy; Transmission line; Indoor installation; Wide band; Robustness; Phase error; Multiple frequency; Fundamental frequency; Backscatter; Range finding; Wide band transmission; Harmonic generation; Vulnerability; Continuous phase; ranging; RF identification (RFID) tags; Simulation; Second harmonic; Heuristic method; Radiofrequency integrated circuits; indoor communication; RFID tag; Radio frequency identification
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2014.2311381

Millimeter-precision meter-distance real-time indoor ranging capability is challenging due to multipath reflections in a rich scattering environment. Traditional continuous wave (CW) phase-based ranging methods, although simple and flexible, are vulnerable to phase offsets and interferences. We improve the previous CW approach by passive broadband harmonic nonlinear-transmission-line (NLTL) tags. Since phase information is now contained within the second harmonic rather than the fundamental frequency, interferences and phase errors caused by direct reflections of the interrogating signal are greatly reduced. By the broadband property of NLTL, a heuristic multi-frequency CW method is formulated to resolve the phase integer ambiguity and to further improve ranging accuracy and robustness even under large phase errors. We present theoretical and simulation analyses, followed by experimental verification.