Phase-based soil moisture sensing using radars and passive backscatter tags
Yu, Angquan
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Permalink
https://hdl.handle.net/2142/127412
Description
Title
Phase-based soil moisture sensing using radars and passive backscatter tags
Author(s)
Yu, Angquan
Issue Date
2024-12-11
Director of Research (if dissertation) or Advisor (if thesis)
Soltonaghai, Elahe
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Soil Moisture Sensing
Digital Signal Processing
Stepped-Frequency Continuous-Wave (SFCW) Radar
Abstract
Soil moisture sensing is important to optimize water usage in agriculture and fire prevention. In agriculture, it enables smart irrigation systems to use water efficiently, reduce wastage, and enhance crop yields. For fire prevention, accurate soil moisture data improves estimates of fuel moisture levels, and helps to raise earlier wildfire warnings. Existing work on soil moisture measurement using RF signals can be categorized into contact-based and contactless methods. Contactless techniques, such as Ground Penetrating Radar (GPR), estimate soil moisture without direct soil contact but face challenges like high cost and limited signal penetration at greater heights. Contact-based methods, like burying a Wifi antenna or Lora antenna under soil, involve deploying sensors or reflectors underground, offering higher accuracy but often requiring complex setups, and high power consumption. This research introduces a hybrid system that integrates SFCW radar technology with wireless backscatter tags, offering a cost-effective, low-maintenance solution for accurate soil moisture sensing. Compared to previous RF-based approaches that buried an active and power-hungry transmitter under the soil, this approach buries a passive backscatter tag, which reflects a square wave from an active radar transmitter back to the receiver. The phase difference between the two antennas of the backscatter tag provides information about soil permittivity, which in turn indicates soil moisture. Controlled experiments demonstrate the the feasibility of inferring soil moisture from phase variations.
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