CSRR-Based Microwave Sensor for Dielectric Materials Characterization Applied to Soil Water Content Determination

Abstract

A new and compact sensor based on the complementary split-ring resonator (CSRR) structure is proposed to characterize the relative permittivity of various dielectric materials, enabling the determination of soil water content (SWC). The proposed sensor consists of a circular microstrip patch antenna supporting a 3D-printed small cylindrical container made out of Acrylonitrile-Butadiene-Styrene (ABS) filament. The principle of operation is based on the shifting of two of the antenna resonant frequencies caused by changing the relative permittivity of the material under test (MUT). Simulations are performed enabling the development of an empirical model of analysis. The sensitivity of the sensor is investigated and its effectiveness is analyzed by characterizing typical dielectric materials. The proposed sensor, which can be applied to characterize different types of dielectric materials, is used to determine the percentage of water contained in different soil types. Prototypes are fabricated and measured and the obtained results are compared with results from other research works, to validate the proposed sensor effectiveness. Moreover, the sensor was used to determine the percentage of water concentration in quartz sand and red clay samples.

Review of Novel and Emerging Proximal Soil Moisture Sensors for Use in Agriculture

“…[57] also developed an invasive open-ended microwave antenna which consisted of a 16 mm diameter by 170 mm long PVC sealed pipe containing a transmitting (TX) and a receiving (RX) dipole antenna, spaced 50 mm apart. Whist [58] reported that they had developed a compact, low cost and easy to manufacture narrowband open-ended antenna microwave sensor for measuring soil moisture.…”

Microwave Sensors Based on Resonant Elements

“…A permittivity sensor based on a CSRR is presented in paper [ 74 ]. The intended application is the determination of soil water content.…”

Noncontact planar microwave sensor for liquid interface detection by a pixelated CSRR ‐loaded microstrip line

“…Microwave sensors based on complementary split‐ring resonators (CSRRs) have been reported in many different sensing situations, such as for magneto‐dielectric materials 6 soil water content, 7 complex permittivity, 8 conductive losses, 9 wireless pressure, 10 ethanol, 11,12 petrol, 13 oil, 14 strain level, 15 and surface cracks 16,17 . The CSRR structures were proposed for increased sensitivity and to reduce the size of the structure.…”