Achieving hundreds-meter ranges in low powered RFID systems with quantum tunneling tags
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Sensor networks, radio equipped drones, and satellites are widely used in many applications such as health care, smart cities and precision agriculture. Nevertheless, the high power costs of communication per distance unit lead to poor technical solutions, particularly in terms of flexibility and efficiency. A future of devices connected through an Internet of Things (IoT) network will require billions of sensors that will affect costs and increase the energy requirements. Backscattering communication through RFID nodes is a promising solution to solve the energy burden of the future, but this technology is still limited in rage and cannot compete yet with the wide coverage advantages of BLE, WiFi, cellular and LoRa networks. Although BLE provides a solid infrastructure for the IoT thanks to largely available BLE-capable devices installed in smart phones, tablets and PCs, the Radio Frequency (RF) front-end of a BLE node is complex and its high power consumption limits portability and require continuous maintenance. Sensor-based RFIDs, on the other hand, require lower orders of magnitude of energy-per-bit for the wireless transfer of information but, despite a simpler RF front-end, their power constraints limit the communications to short ranges. This research aimed to design a power-stingy backscattering device able to cover an area so wide to enable the use of RFID communications for new applications. The outcome of this work is a highly sensitive 5.8 GHz quantum tunneling RFID tag that achieves backscattering ranges above 1.2 km while consuming biasing powers as low as 20 uW and a radio communication efficiency of 2.9 pJ/bit. This is over 10 times higher than the maximum range of a semi-passive 5.8 GHz RFID link and more than 1000 times lower energy per bit than WiFi (IEEE 802.11ac). Moreover, this device is characterized by a simple RF front-end, by modulation speeds as high as 7 MHz, a sensitivity of -84 dBm, and increasing SNRs for increasing RF impinging powers. This work lays out the basis for both entrepreneurial and research activities that will lead to a new class of long-range backscattering passive sensors with power consumption far lower than traditional radios.