An OOK Chirp Spread Spectrum Backscatter Communication System for Wireless Power Transfer Applications

• Published in: IEEE transactions on microwave theory and techniques Vol. 69; no. 3; pp. 1838 - 1845
• Main Authors: Belo, Daniel, Carvalho, Nuno Borges
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-03-2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplitude modulation; Amplitude shift keying; Backscatter; Backscatter (BS) communications; Backscattering; Chirp; chirp spread spectrum (CSS); Circuits; Communications systems; Internet of Things (IoT); Keying; Low-power electronics; Power management; Spread spectrum; Spread spectrum communication; Spread spectrum transmission; Voltage controlled oscillators; Wireless communication; wireless power transfer (WPT); Wireless power transmission; wireless sensor network (WSN)
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2020.3041249

In this work, a general-purpose wireless energy receiving unit with improved backscatter (BS) communications capabilities assisted by far-field wireless power transfer (WPT) techniques is proposed. The unit employs an auxiliary RF-to-dc converter circuit which is used to simultaneously power and tune a low-power voltage controlled oscillator (VCO). By doing so, a relation between its frequency of oscillation and the instantaneous available RF input power is established. It is shown that by adding a small amplitude modulation to the wireless power carrier, the device can generate a linear frequency modulated signal which is used to provide low-power and long-range ON-OFF keying (OOK) chirp spread spectrum (CSS) BS communications. Experimental validation in real scenarios is provided, showing its superiority against the well-known conventional BS amplitude shift-keying (ASK) modulation scheme. Moreover, contrary to other designs, it is demonstrated that the proposed design does not need a dedicated processing unit to generate the required baseband signals, allowing to save power and complexity.