Low-energy and spectrally-efficient IoT sensors with low-cost additive manufacturing
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This thesis develops low-energy and low-cost communication and powering modules for sensors and devices for the Internet of Things (IoT). To minimize the energy footprint of IoT sensors, backscatter radio is utilized for communication, instead of power-demanding active radios. Custom tag front-ends are designed to increase the sensors' maximum range and incorporate RF energy harvesters for battery recharging or battery exclusion. Custom, non-conventional front-ends are proposed that a) maximize the backscattering efficiency and operating range, b) generate smooth, arbitrary waveforms for reduced per-sensor bandwidth occupancy which allows high network density, c) boost datarates up to the Gigabit-range by utilizing mmWave frequency bands. RF harvesting front-ends are developed to complement the communication front-ends, taking into account the complex requirements of the IoT: hassle-free device deployment without knowledge/predetermined RF source positions or frequency bands. Additive manufacturing (3D- and inkjet- printing) are fully exploited to build compact Origami-reconfigurable packages with embedded antennas and front-ends or fully-flexible and miniaturized printed communicators and harvesters that can be integrated to wearables and small portable devices. The broad range of modules presented in this thesis will reduce the complexity of IoT nodes ranging from low-bitrate, long-range sensors at UHF frequencies up to ultra-wideband backscatter communicators operating at mm-Wave bands for real-time, high-datarate applications.