24μ Watt 26m range batteryless backscatter sensors with FM remodulation and selection diversity

Summarization: Reflection radio principles, used in RFID systems, have been recently exploited in wireless sensor networking, due to their inherent low-power requirements. This work offers a complete batteryless analog sensor design, implemented and tested in real-world conditions, able to backscatter its sensed information, without any type of analog-to-digital converter (ADC), digital logic or dedicated illuminator, towards any off-the-shelf FM receiver. Selection diversity exploited simultaneous illumination from multiple FM broadcasting stations, located 6.5 km away. Sensor-to-smartphone distance of 26 and 15 meters, outdoors and indoors, respectively, was experimentally demonstrated at (audio) output SINR of 10 dB. The ultra-low cost circuit consumed measured power of 24μ Watt in continuous and batteryless operation, tested with various ambient power sources. The design can in principle accommodate various resistive or capacitive sensors that can be literally 'listened' by a single, conventional FM receiver (e.g., in a smartphone).Presented on