Measurement of the broadband complex permittivity of soils in the frequency domain with a low-cost Vector Network Analyzer and an Open-Ended coaxial probe
The performance of a handheld Vector Network Analyzer (VNA), the nanoVNA, a low-cost, open-source instrument, was evaluated. The instrument measures the complex permittivity of dielectric media from 1-port reflection parameters in the 1 – 900 MHz bandwidth. We manufactured an open-ended coaxial prob...
| Autores: | , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universidad Politécnica de Cartagena(UPCT) |
| Repositorio: | Repositorio Digital UPCT |
| OAI Identifier: | oai:repositorio.upct.es:10317/12127 |
| Acceso en línea: | http://hdl.handle.net/10317/12127 https://doi.org/10.1016/j.compag.2022.106847 |
| Access Level: | acceso abierto |
| Palabra clave: | Complex permittivity Soil spectroscopy Frequency domain reflectometry Soil moisture Open-ended coaxial probe nanoVNA Low-cost instrument Vector network analyzer Dielectric dispersion Ecologíal Electrónica Ingeniería Eléctrica Tecnología Electrónica Tecnologías del Medio Ambiente 3306 Ingeniería y Tecnología Eléctricas 2410.05 Ecología Humana |
| Sumario: | The performance of a handheld Vector Network Analyzer (VNA), the nanoVNA, a low-cost, open-source instrument, was evaluated. The instrument measures the complex permittivity of dielectric media from 1-port reflection parameters in the 1 – 900 MHz bandwidth. We manufactured an open-ended coaxial probe using a SMA-N coaxial adapter to perform dielectric measurements. The accuracy of the nanoVNA was comparable to that of a commercial VNA between 1 and 500 MHz according to tests in reference organic liquids, while a lack of stability was found beyond 700 MHz. The self-manufactured open-ended coaxial probe was subjected to a Finite Element Method (FEM) analysis and its electromagnetic (EM) field penetration depth was determined to be 1.5 mm at 100 MHz, being reduced to 1.3 at 900 MHz and thus demonstrating a frequency-dependent support volume. The broadband complex permittivity of three mineral soils of varied textures was obtained for a range of bulk densities and water contents from dry to water-saturated conditions. The dielectric response of the soils approximated the well-known Topp et al. (1980) equation at high frequencies. At lower frequency however, higher permittivities were exhibited due to dielectric dispersion, which emphasizes the importance of EM-based soil moisture sensor operating frequency when considering sensor calibration or comparing the response of different sensors. |
|---|