volume | PIER Journals

Abstract

This paper presents the design, fabrication and experimental validation of a novel compact high-gain decagonal microstrip patch antenna designed for noninvasive soil moisture sensing. The antenna utilizes the strong correlation between its dielectric properties and soil moisture content, which directly influences the antenna's reflection coefficient and resonant frequency. The decagonal geometry using a Taconic TLY-5 substrate achieves a high gain of 7 dBi and an excellent radiation efficiency of 96.5% compared to the FR-4 substrate. The prototype antenna fabricated on Taconic TLY- substrate resonates at 2.445 GHz frequency with a measured reflection coefficient of -34.3 dB, validating the high-performance characteristics predicted by full-wave simulations using CST Studio Suite 2018. The sensing capability of the fabricated antenna is carefully tested across sandy, loamy, and clay soils, demonstrating a predictable downward shift in resonant frequency as moisture content increases. A linear regression analysis is performed on the experimental data from sandy, loamy, and clay soils, yielded a high coefficient of determination (R² ≈ 0.9) for all three soil types, establishing a calibration model to accurately convert the resonant frequency shifts into soil moisture values. The obtained sensitivity values for soil moisture detection are 4.76 MHz/% for sandy soil, 5.15 MHz/% for loamy soil and 4.89 MHz/% for clay soil respectively. The compact size, high gain and consistent performance across different soil samples make this proposed antenna a better solution for precision agriculture and environmental monitoring through integration into wireless sensor networks.

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Dr. Sahana K

Dr. Bharathraj Kumar M