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Backscatter radios with LimeSDR

Giannakopoulos Konstantinos-Orestis

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Year 2020
Type of Item Diploma Work
Bibliographic Citation Konstantinos-Orestis Giannakopoulos, "Backscatter radios with LimeSDR", Diploma Work, School of Electrical and Computer Engineering, Technical University of Crete, Chania, Greece, 2020
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This dissertation presents two backscatter radio applications for wireless sensor networks with the low-cost software-defined radio (SDR) LimeSDR platform. Two different architectures are developed. The first application implements a monostatic receiver, where the LimeSDR is configured as both the RF-tag's illuminator, as well as the receiver of the backscattered signal. It is found that the monostatic architecture in combination with the transmitting power capabilities of the LimeSDR board (2 dBm output power) can achieve a range of 9.4 meters. The range coverage increased to 13.7 meters with the use of an external amplifier. The second application presents a reader for ambiently-powered scatter radio sensors that exploit the FM broadcast signals for illumination. In this architecture, the source of the illuminating signal is located 7 kilometers away. The backscattered signal is also an FM audio signal with a frequency that corresponds to the sensors' measurement. The receiver demodulates the signal and detects the frequency using periodogram-based Fourier analysis. The maximum range achieved between the sensor and the reader for this architecture, with a root mean square error (RMSE) less than 200 Hz, was 7 meters. Both applications implement low-cost radio link communication exploiting the fact that scatter radio, in principle, requires low energy consumption and simple hardware demands. Additionally, a WiFi adhoc network link was implemented with a USB adapter to transfer the sensed information to a central node/base station. TCP and UDP protocols were tested for range maximization between the reader and base station. UDP protocol achieved the maximum range coverage of approximately 146 meters. Experiments on soil moisture measurements were conducted to test the efficiency and the range coverage of each system.

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