【作者】 杨国辉；

【导师】 谭久彬；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2006， 硕士

【摘要】 水分是影响农作物、食品和矿物等产品品质的根本因素。传统的微波透射法,由于其微波耦合到自由空间,测量易受到外界干扰,测量精度很难再有实质性提高。而以谐振腔作为测量物料水分的传感器,由于被测物料位于腔体内部,不适合工业在线测量的应用。因此,有必要研制一种使用开路同轴谐振腔作为传感器的测量系统,实现快速、高精度的测量。本课题“基于微波谐振腔的物料水分传感器研制”采用谐振腔进行物料水分测量中所涉及的理论、方法和关键技术进行深入的研究,主要研究工作如下:首先,通过系统分析国内外微波法物料水分测量技术的发展现状,指出高精度、快速的物料水分测量已经成为相关生产加工领域面临的主要问题;在分析现有水分测量方法的基础上,指出红外法、自由空间微波法在水分测量中存在的不足。基于此提出了一种开路同轴谐振腔水分传感器。提出了一种基于同轴谐振腔微扰原理的谐振微波传感模型,从谐振腔微扰原理出发,利用时域有限差分法(FDTD)对谐振腔空间进行网格划分并求解,建立了谐振腔传感模型。以该模型为基础,系统分析了传感器和物料作用后的内外电磁场分布。利用FDTD方法和CST软件,研究了谐振腔空载谐振频率及开口保护盖材质对测量精度的影响。仿真结果表明:选择2.45GHz作为谐振频率可以较好地平衡测量非线性和分辨力两个因素;开口保护盖材质影响测量分辨力。研究了谐振腔传感器应用于在线测量的安装方法和相应物料传送结构。最后,研究了实验样品的制备过程。对同轴开路谐振腔水分传感器的稳定性、分辨力和重复性进行了实验研究。更多还原

【Abstract】 The quality of materials such as crop, food and mineral is influeced by moisture content. The traditional measurement method using microwave transmission technique distributes electromagnetic fields in free space easily which makes it hard to improve measurement precision. Resonant cavity sensor is not suitable for on-line industry applications because the measured material is inside. It is necessary to develop an open-ended coaxial resonant sensor to obtain rapid and high precise measurement.In this study, some key technologies, related theories and methods on designing microwave coxial resonant moisture sensor, are adopted and researched. The main reaearch works are as follows:Firstly, high precise and rapid moisture content measurements have become the main problem that some industries face. On the base of analyzing existing moisture content measurement techniques, some disadvantages about infrared and free space microwave are presented. So open-ended coaxial resonant cavity as moisture content sensor are presented.An open-ended coaxial resonant cavity for moisture content sensor is presented and developed. On perturation theory resonant cavity model is built by FDTD dividing grids of resonant cavity space and solving them. On the base of the model, electromagnetic fields distribution inside and outside of resonant cavity, also noload resonance frequency and cover material’s influences on measurement precision are analyzed. Otherwise installation manner and transfer system on line for resonant cavity sensor are designed. Simulation results show that taking 2.45GHz as resonance frequency balances measurement nonlinearity and resolution well, and cover material can infulence the measurement resolution. Last, samples prepared for experiment are introduced. Experiments of stability, resolution and repeatability on open-ended resonant cavity sensor are researched.更多还原