Radio Frequency Energy Harvesting for Embedded Sensor Networks in the Natural Environment
Radio Frequency Energy Harvesting for Embedded Sensor Networks in the Natural Environment
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发表时间：
2012-04
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通讯作者：
Z. W. Sim
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作者：
Z. W. Sim
农业领域是无线传感器网络(WSNs)的新兴应用领域。这就要求传感器节点部署在室外环境中，以便监测相关的自然特征，如土壤状况或虫害。有限的能源供应和随后的电池更换是这些农业传感器节点的共同问题。一种可能的解决方案是使用能量收集，即提取环境能量并将其转换为可用电力形式，为无线传感器供电。本论文研究了在特定应用中使用射频(RF)能量采集的可行性，即为在室外环境中运行的一类无线地面农业传感器网络供电。调查主要是通过对这一主题的文献研究进行的。论文的第一部分研究了几种能量采集/无线能量传输技术，这些技术可能适用于为目标农业WSN节点供电。确定了每种技术的主要优点和局限性，并给出了选择远场射频能量采集作为研究技术的理由。然后进行基于理论的系统分析，试图确定所有相关的设计参数，并量化它们对系统性能的影响。还包括射频链路预算分析，以检查使用射频能量采集来为样本WSN节点供电的可行性。Zyrox2诱饵站。论文的第二部分重点研究了两种能量采集天线的设计。第一种设计是基于空气基板的具有固体接地面的折叠短路贴片天线(FSPA)，第二种设计是类似的FSPA结构，在其接地面中嵌入四对缝隙。这两种天线都是在电波暗室和实际工作环境中进行模拟、制造和测试的。户外田野。此外，使用商用现成组件构建的功率采集器电路在实验室中使用射频信号发生器源进行了测试。对室内试验和田间试验结果进行了分析。对所使用的测量技术进行了回顾，并对如何改进它们提出了一些意见。在明确确定这一应用的可行性和可行实施之前，必须对射频能量收集器进行进一步的工作，特别是在改进天线设计方面。
The agricultural sector is an emerging application area for Wireless Sensor Networks (WSNs). This requires sensor nodes to be deployed in the outdoor environment so as to monitor pertinent natural features, such as soil condition or pest infestation. Limited energy supply and subsequent battery replacement are common issues for these agricultural sensor nodes. One possible solution is to use energy harvesting, where the ambient energy is extracted and converted into usable electrical form to energise the wireless sensors. The work presented in this thesis investigates the feasibility of using Radio Frequency (RF) energy harvesting for a specific application; that is powering a generic class of wireless ground-level, agricultural sensor networks operating in an outdoor environment. The investigation was primarily undertaken through a literature study of the subject. The first part of the thesis examines several energy harvesting/ wireless energy transfer techniques, which may be applicable to power the targeted agricultural WSN nodes. The key advantages and limitations of each technique are identified, and the rationale is being given for selecting far-field RF energy harvesting as the investigated technique. It is then followed by a theoretical-based system analysis, which seeks to identify all relevant design parameters, and to quantify their impact on the system performance. An RF link budget analysis was also included to examine the feasibility of using RF energy harvesting to power an exemplar WSN node ? Zyrox2 Bait Station. The second part of the thesis focuses on the design of two energy harvesting antennas. The first design is an air-substrate-based folded shorted patch antenna (FSPA) with a solid ground plane, while the second design is a similar FSPA structure with four pairs of slot embedded into its ground plane. Both antennas were simulated, fabricated and tested inside an anechoic chamber, and in their actual operating environment ? an outdoor field. In addition, a power harvester circuit, built using the commercially available off-the-shelf components, was tested in the laboratory using an RF signal generator source. The results from both the laboratory and field trial were analysed. The measurement techniques used were reviewed, along with some comments on how to improve them. Further work on the RF energy harvester, particularly on the improvement of the antenna design must be carried out before the feasibility and viable implementations for this application can be definitively ascertained.