Effect of moisture content variation on dielectric properties of various plant leaves at microwave frequencies

Abstract

Overview

This study investigates the complex permittivity of Corn, Jowar, Ashoka, and Banana plant leaves across a broad microwave frequency range (500 MHz to 15 GHz). Measurements were performed using a Vector Network Analyzer, specifically the Anritsu Shockline Model-MS46322A, with the leaves at varying moisture contents.

Findings

• Both dielectric constant (e') and dielectric loss (e") of the tested leaves decrease as the moisture content decreases within the examined frequency range.
• For leaves below a certain critical moisture level (CML), values of e' and e" stay almost unaffected by frequency variation, indicating a plateau at low moisture.
• The dielectric loss (e") does not significantly rise with increased moisture up to the CML, and this critical level varies by plant type.
• At higher moisture content, both e' and e" display significant frequency dependence.
• When moisture in leaves exceeds a certain threshold, e" increases slowly with frequency beyond 3 GHz, approaching the relaxation properties of water.
• Measured values for leaf extracts matched well with those calculated from the Stogryn equations (for equivalent salinity).
• Empirical results were also in strong agreement with outcomes predicted using the Debye-Cole dual dispersion dielectric model.

Conclusion

The dielectric behavior of plant leaves under microwave frequencies is greatly influenced by moisture content, which in turn impacts their response to electromagnetic fields across the microwave spectrum. Understanding these properties is crucial for applications involving EMF exposure, and highlights a potential link between material characteristics and microwave energy absorption in biological matrices.