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

João G. D. Oliveira,Erica N. M. G. Pinto,Adaildo G. D’Assunção,Valdemir P. Silva Neto

doi:10.3390/s20010255

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.

Highlights

Recent technological advances related to wireless and mobile communication technologies, increasingly demanding high transmission rates and low latency, have aroused the interest of researchers worldwide in the development of sensors that can get information on the electromagnetic characteristics of dielectric materials present in the communication channel or used in the manufacture of microwave devices and circuits.Several analysis techniques have been developed but the most interesting are those with noninvasive and nondestructive characteristics with respect to the material under test (MUT)
Substrate integrated waveguide (SIW) sensors are developed to characterize the complex permittivity of microfluidics [1,2] or are submerged in the liquid under test (LUT) [4,5]
The proposed sensor was initially modeled as a circular microstrip antenna patch antenna (Figure 1a), operating at 3.1 GHz, with a quarter-wavelength impedance matching circuit and a complementary split-ring resonator (CSRR) slotted element, as shown in Figure 1b, which caused a resonance frequency shift to 2.26 GHz and the emergence of a second resonance at 3.5 GHz

Summary

Introduction

Recent technological advances related to wireless and mobile communication technologies, increasingly demanding high transmission rates and low latency, have aroused the interest of researchers worldwide in the development of sensors that can get information on the electromagnetic characteristics of dielectric materials present in the communication channel or used in the manufacture of microwave devices and circuits.Several analysis techniques have been developed but the most interesting are those with noninvasive and nondestructive characteristics with respect to the material under test (MUT). Recent technological advances related to wireless and mobile communication technologies, increasingly demanding high transmission rates and low latency, have aroused the interest of researchers worldwide in the development of sensors that can get information on the electromagnetic characteristics of dielectric materials present in the communication channel or used in the manufacture of microwave devices and circuits. Planar sensors can be classified into several groups according to their application, principle of operation, or even the intrinsic characteristics of the used resonator. There is the group of planar sensors used in the characterization of microfluidics, which has been considered by several researchers [1,2,3,4,5]. Substrate integrated waveguide (SIW) sensors are developed to characterize the complex permittivity of microfluidics [1,2] or are submerged in the liquid under test (LUT) [4,5].

Methods

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Discussion

Conclusion