soil moisture sensing via swept frequency based microwave sensors基于土壤水分遥感通过扫频微波传感器.pdf

Sensors 2012, 12, 753-767; doi:10.3390/s120100753 OPEN ACCESS sensors ISSN 1424-8220 /journal/sensors Article Soil Moisture Sensing via Swept Frequency Based Microwave Sensors Mathew G. Pelletier 1,*, Sundar Karthikeyan 2, Timothy R. Green 3, Robert C. Schwartz 4, 1 1 John D. Wanjura and Greg A. Holt 1 USDA-ARS, Cotton Production and Processing Unit, Lubbock, TX 79403, USA; E-Mails: john.wanjura@ (J.D.W.); greg.holt@ (G.A.H.) 2 Rain Bird Corp., San Diego, CA 92123, USA; E-Mail: skarthikeyan@ 3 USDA-ARS, Agricultural Systems Research Unit, Fort Collins, CO 80526, USA; E-Mail: tim.green@ 4 USDA-ARS, Soil and Water Management Research Unit, Bushland, TX 79012, USA; E-Mail: robert.schwartz@ * Author to whom correspondence should be addressed; E-Mail: Mathew.Pelletier@; Tel.: +1-806-746-5353. Received: 24 November 2011; in revised form: 28 December 2011 / Accepted: 29 December 2011 / Published: 11 January 2012 Abstract: There is a need for low-cost, high-accuracy measurement of water content in various materials. This study assesses the performance of a new microwave swept frequency domain instrument (SFI) that has promise to provide a low-cost, high-accuracy alternative to the traditional and more expensive time domain reflectometry (TDR). The technique obtains permittivity measurements of soils in the frequency domain utilizing a through transmission configuration, transmissometry, which provides a freq