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

这个小型企业创新研究(SBIR)第一阶段项目将开发分离超快上升时间事件和反射阶跃函数的新技术，这是开发用于土壤水分测量的集成差分时域反射仪(TDR)所需的。由于端接在可变土壤负载中的电路板带状线的残余反射，以及来自湿润锋和土壤中的不连续性的反射，传播时间、介电常数和水分的推导容易受到虚假的较短时间的反射与来自波导末端的主要反射的矢量相加所引起的误差。干扰杂散信号的特征随土壤环境的不同而变化。在TDR数字化仪处出现的整个波形是入射阶跃、反射波和一组杂散信号的合成图像。所需要的研究是表征杂散信号的模式，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的推导的影响。湿润锋的识别和计时也将包括在内，为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、易于部署的准确测量土壤水分含量的手段，包括可靠地测量粮食作物的吸水量。这一能力将有助于显著提高水的利用效率--这是用更少的水种植高质量食物的基础。对作物种植者来说，价值主张是降低边际成本，提高作物产量和质量，潜在的回报时间为一到两个生长季。商业采用土壤湿度传感技术将有助于管理增加的成本和淡水需求，其中70%以上的用水量用于农业。该技术还将为研究和监测流域动态、洪水和干旱预测、监测大坝、泥石流地区和堤坝的潜在破坏以及研究土壤水动力学对天气的影响提供稳定可靠的测量工具。目前用于这些测量的工具要么监管严格(中子探头)，安装困难(时域透射仪探头)，要么提供随土壤电导率和紧实度变化而不稳定的读数(电容式探头)。

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).