Thermo-Harvested Autarkic Wireless Integrated Transmitter (THAWIT)

对于一般的物联网，特别是医疗传感器，需要低功率的无线数据发射器。到目前为止，大多数这样的发射机需要电池或低效的射频(RF)采集。在THAWIT，我们想要研究和演示第一个无线数据发射器，它可以通过紧凑、集成、热电采集的方式提供。要实现供应自给自足，我们必须应对以下挑战。发射机的功耗必须大幅降低。此外，还必须提高热电器件的功率密度。一个主要的挑战是在硅上集成的能力，限制了可能的材料成分。我们希望开发出前沿功率密度超过10μW/mm~2、中等温差为7K的硅兼容收获元件。为了实现这一雄心勃勃的目标，我们严格优化了几何结构和材料成分。高输出功率密度需要较高的热电极臂高，影响热电材料的光致抗蚀剂和沉积参数的选择。为了降低p型温差电桥臂的导热系数，研究了一种新的工艺。此外，我们开发了一种硅兼容的微型超级电容器作为能量缓冲器。为了能够与IFW的制造技术和设备兼容，我们通过高性能的全固态叉指平面内微型超级电容器来实现这一点。它是基于光刻刻画的溅射电极和固体电解质。考虑到节能损耗和2mm2的元件面积，cmos发送器必须在10μW或更小的直流功率下工作。为了实现这样的超低直流功率，我们研究了直接调制振荡器，它具有大约0.1%的积极占空比、超快的斜坡上升和睡眠阶段的小型化泄漏。除了需要缓冲放大器的阻抗匹配天线外，我们还考虑了可以直接集成到振荡器的LC谐振器中的电感天线。为演示器设计了一种与纺织品兼容的编织或印花天线。演示者应按照医疗植入物通信服务(MICS)进行操作。最终目标是展示400 MHz左右的数据传输，数据速率为1-10kb/S，距离长达1米。THAWIT结合了IFW的Gabi Schierning和TUD的Frank Ellinger在热电设备领域在低功率集成电路方面的互补能力。

For the internet of things in general and medical sensors in particular, low power wireless data transmitters are required. Up to date, most of such transmitters require batteries or inefficient radio frequency (RF) harvesting. In THAWIT, we want to investigate and demonstrate the first wireless data transmitter, which can be supplied by means of compact, integrated, thermo-electric harvesting. To allow supply-autarkic operation, we have to meet the following challenges. The power consumption of the transmitter must be massively reduced. Moreover, the power density of the thermoelectric devices must be increased. A major challenge is the capability for integration on silicon limiting the possible material compositions. We want to develop silicon-compatible harvesting elements with a leading-edge power density beyond 10 μW/mm2 at a moderate temperature difference of 7 K. To meet this ambitious goal, we rigorously optimise the geometry and material compositions. A high thermoelectric leg height is necessary for high output power density, affecting the choice of the photoresist and deposition parameters of the thermoelectric material. A new process for the p-type thermoelectric leg is researched to reduce the thermal conductivity. In addition, we develop a silicon-compatible micro-supercapacitor serving as energy buffer. To enable compatibility with the fabrication technology and equipment at IFW, we realize it by a high-performance all-solid-state interdigital in-plane micro-supercapacitor. It is based on photo-lithographically patterned sputtered electrodes and a solid electrolyte. Considering energy saving losses and component areas of 2 mm2, the CMOS transmitter must operate with a dc power of 10 μW or less. To enable such an ultra-low dc power, we study direct modulated oscillators with aggressive duty-cycling of around 0.1 %, ultra-fast ramp-up and miniaturized leakage in the sleep phases. In addition to impedance-matched antennas requiring buffer amplifiers, we consider also inductive antennas which can be directly incorporated in the LC-resonator of the oscillator. A textile-compatible woven or printed antenna is designed for the demonstrator. The demonstrator shall operate according to the medical implant communication service (MICS). The final goal is to show data transmission around 400 MHz with a data rate of 1-10 kb/s for distances of up to 1 meter. THAWIT combines the complementary competences of Gabi Schierning, IFW, in the area of thermoelectric devices, and Frank Ellinger, TUD regarding low power integrated RF circuits.