An Antenna System Sensor for Soil Moisture Sensing

In this article, an antenna system sensor for soil moisture sensing is proposed. The antenna sensor comprises the parasitic irregular structure-based double-spiral resonator (PI-DSR), the double-spiral resonator (DSR), a radiating patch, a microstrip feeding structure, and an integrated polydimethylsiloxane (PDMS) container. The ultrawideband (UWB) performance is achieved by smoothly transitioning the edges of the radiation patch and etching the circular slot on the ground. By employing the PI-DSR, the antenna sensor can generate rectangular band-notched characteristics. To separate the sensing and communication functionalities, a second notch structure using the DSR is located on the bottom of the substrate. Information transmission rate is significantly increased by arranging four antenna sensor elements to form an antenna system sensor. Furthermore, positioning the PDMS container containing soil specimens onto the DSR of the sensor facilitates the measurement of soil moisture content. By leveraging the variation in dielectric constant associated with different soil moisture levels, the sensor achieves a shift in the notch frequencies, thereby enabling the detection of soil moisture content. The sensitivity of the sensor can reach 5.95 MHz/%. The decoupling of communication and sensing frequency bands facilitates independent operation between the antenna and sensor, mitigating the potential for communication disruptions. Additionally, the proposed antenna sensor exhibits multielement transmission capabilities, thereby augmenting both the accuracy and efficiency of sensing operations. The antenna sensor exhibits notable advantages, including compact size, high detection accuracy, minimal sample volume, nonintrusive measurement capability, and high reliability.