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Communications by Means of Reflected Power: Long Range Semi-Passive Radio Frequency Backscatter Communication

Housden, D; (2016) Communications by Means of Reflected Power: Long Range Semi-Passive Radio Frequency Backscatter Communication. Doctoral thesis , UCL (University College London).

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Abstract

Radio frequency (RF) backscatter communication systems use a powered interrogator to transmit RF energy towards a remotely located device. The device modulates the reflection of the interrogator’s RF energy to send data wirelessly from the device back to the interrogator. The objective of this thesis is to develop a backscatter data communication system to operate over at least 800 m with an interrogator that is radio licence-exempt in Europe. The prior art in backscatter communications is critically reviewed. Three backscatter communication systems are identified that achieved over 800 m range but all used interrogator transmission powers tens of millions of times higher than allowed under a European licence-exemption. To achieve the objective a significant improvement in the system efficiency is required. This thesis examines backscatter modulation techniques for data transmission. Harmonic generation and amplitude modulation (AM) techniques are selected for further investigation. System models are developed and verified experimentally for both systems. Predictions are made of the maximum standoff range for licence-exempt systems satisfying the objective of this thesis. The harmonic system is predicted to achieve 82 m at 2.45 GHz with a data-rate of 86.5 kbps and the AM system between 416 m and 1648 m at 867.5 MHz with a data-rate of 126 kbps. A long range trial of the AM system was conducted and semi-passive backscatter communication over 1050 m was achieved licence-exempt as per the thesis objective, with a potential data rate of just over 1 Mbps. The smaller size, weight and power of backscatter communication devices would make them ideal for applications such as high-voltage electricity substations, battlefields and satellite emergency telemetry. They would enable communications in extreme environments where there is limited access to the device and where changing batteries would be difficult or dangerous.

Type: Thesis (Doctoral)
Title: Communications by Means of Reflected Power: Long Range Semi-Passive Radio Frequency Backscatter Communication
Event: University College London
Language: English
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
URI: http://discovery.ucl.ac.uk/id/eprint/1513346
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