SDR reader for passive backscatter sensors

• Main Author: Batista, Diogo Manuel Policarpo
• Publication Date: 2019
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10773/29638
• topic: IoT; Backscattering; Wireless sensor networks; Reader; Receiver; Digital signal processing; SDR; Python

As the Internet of Things concept moves closer to reality, some technological gaps come to light and require addressing. Advancements in reader technology are needed in order to achieve higher degrees of capability and adaptability at lower costs. Conventional readers are currently priced in the range of thousands of euros. It’s crucial to lower this entry barrier, because the lower it gets, the more attractive IoT solutions will become and the faster the global network of sensors will grow. Improvements in the performance and cost of single board computers such as the Raspberry Pi and also of RF front-ends such as the RTL-SDR have opened the way to a new class of ultra-low-cost readers. This dissertation aims to explore a new possibility of reception and demodulation of an RF signal transmitted from a passive sensor using the aforementioned technologies. The final prototype’s architecture was designed and implemented to facilitate the reception, conditioning and discretization/quantization of the ASK modulated RF signal by the RTL-SDR based front-end, so that it can then be sent via USB into the Raspberry Pi where its information will be processed through steps such as filtering, decimating, demodulating, validating and integrating into the network. This process is first introduced under the architectural point of view and then, under a more detailed approach, in a description of the implementation. Testing results are presented with variations of antenna distance and decimation ratio. The prototype was tested in laboratory and field environments and the results are promising. Also included are some potential future development suggestions and a package of development tools.