SBIR Phase I: Low-cost Time-domain Reflectometer for Soil Water Content Reporting in Precision Agriculture

这个小企业创新研究（SBIR）第一阶段项目将开发新技术，用于分离超快上升时间事件和反射阶跃函数，用于开发用于土壤含水量测量的集成差分时域反射仪（TDR）。 由于来自终止于可变土壤负载的电路板带状线的残余反射以及来自土壤中的润湿前沿和不连续性的反射，传播时间、介电常数和含水量的推导受到由寄生的、短期反射与来自波导端部的主反射的矢量相加所引起的误差的影响。干扰杂散信号的特性随土壤环境而变化。 出现在TDR数字化仪上的整个波形是入射阶跃、反射波和一组寄生信号的合成图像。 所需的研究是表征虚假信号模式，并开发机器学习和信号处理算法，以消除它们对反射波传播时间推导的影响。 还将包括湿润锋的识别和定时，以向传感器用户提供渗透监测能力。该项目更广泛的影响/商业潜力是提供一种负担得起和易于部署的方法，准确测量土壤含水量，包括可靠地测量粮食作物的吸水量。这一能力将促进水资源利用效率的显著提高，这是用更少的水种植高质量食物的基础。 对作物种植者的价值主张是降低边际成本，提高作物产量和质量，潜在的投资回收期为一到两个生长季节。 土壤湿度传感技术的商业化应用将有助于管理不断增加的淡水成本和需求，其中超过70%的淡水消耗用于农业。 该技术还将提供一个稳定和可靠的测量工具，用于研究和监测流域动态，以预测洪水和干旱，监测水坝、泥石流区和堤坝的潜在故障，并研究土壤水分动态对天气的影响。目前用于这些测量的工具要么是严格管制的（中子探针），难以安装（时域透射仪探针），要么是随着土壤电导率和压实度的变化而提供不稳定的读数（电容探针）。

This Small Business Innovation Research (SBIR) Phase I project will develop new technology for the separation of ultra-fast-rise-time incident and reflected step functions needed for the development of an integrated differential Time Domain Reflectometer (TDR) to be used in soil water content measurement. Because of residual reflections from circuit board striplines terminated in variable soil loads and reflections from wetting fronts and discontinuities in the soil, the derivation of propagation time, permittivity and water content are subject to errors caused by the vector addition of the spurious, shorter-term reflections with the main reflection from the end of the waveguide. The characteristics of the interfering spurious signals vary with the soil environment. The overall waveform appearing at the TDR digitizer is a composite image of an incident step, a reflected wave and the set of spurious signals. The research required is that of characterizing the spurious signal patterns and of developing machine learning and signal processing algorithms to remove their impact from the derivation of reflected wave propagation time. Identification and timing of wetting fronts will also be included to provide sensor users with infiltration monitoring capability. The broader impact/commercial potential of this project is to provide an affordable and easily deployed means of accurately measuring soil water content, including the credible measurement of water uptake by food crops. This capability will facilitate significant increases in water use efficiency - the foundation for growing high quality food with less water. The value proposition to crop growers is reduced marginal costs and increased crop yield and quality, with a potential payback time of one to two growing seasons. Commercial adoption of soil moisture sensing technology will help manage the increased cost and demand for fresh water, of which over 70% of consumption goes to agriculture. The technology will also provide a stable and credible measurement tool for studying and monitoring watershed dynamics for flood and drought prediction, for monitoring dams, mudslide areas and levees for potential failure and for studying the impact of soil water dynamics on weather. Current tools for these measurements are either heavily regulated (neutron probe), difficult to install (Time Domain Transmissometer probe) or provide unstable readings with changing soil electrical conductivity and compaction (capacitive probes).