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

这项小型企业创新研究（SBIR）第一阶段项目将开发分离超快速上升时间入射和反射阶跃函数的新技术，用于开发用于土壤含水量测量的集成差分时域反射仪（TDR）。由于在可变土壤载荷下终止的电路板带状线的残余反射以及湿润锋面和土壤不连续面的反射，传播时间、介电常数和含水量的推导受到矢量添加的误差的影响，这些误差是由来自波导末端的主反射的虚假、短期反射引起的。干扰杂散信号的特性随土壤环境的变化而变化。在TDR数字化仪上出现的整体波形是一个入射阶跃、一个反射波和一组杂散信号的合成图像。需要进行的研究是表征伪信号模式，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。还将包括湿锋的识别和定时，为传感器用户提供渗透监测能力。该项目的更广泛的影响/商业潜力是提供一种经济实惠且易于部署的精确测量土壤含水量的方法，包括可靠地测量粮食作物的吸水量。这种能力将有助于显著提高水的利用效率，这是用更少的水生产高质量粮食的基础。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控制淡水成本和需求的增加，其中超过70%的淡水消耗用于农业。该技术还将为研究和监测流域动态以进行洪水和干旱预测、监测水坝、泥石流区和堤坝的潜在破坏以及研究土壤水动态对天气的影响提供稳定和可靠的测量工具。目前用于这些测量的工具要么是严格调节的（中子探头），难以安装（时域透射探头），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（电容探头）。

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).