Non-Destructive Moisture Content Measurement Using X-Band Rectangular Waveguide: Theory, Simulation, and Experimental Validation

¹ Information and Communication Technology Laboratory (Labtic) National School of Applied Sciences, University of Abdelmalek Essaadi Tangier, Morocco
² Research Group in Emerging and Sustainable Technologies Faculty Multidisciplinary, Abdelmalek Essaadi University Larache, Morocco
³ Biomécanique & Microsystems, National School of Applied Sciences, Abdelmalek Essaadi University, Tangier, Morocco
⁴ Secure and Mixed Architecture for Reliable Technologies and Systems (SMARTS) National Institute of Posts and Telecommunications, Rabat, Morocco

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 3 August 2026

Abstract

We present a novel non-destructive method for estimating the moisture content of solid materials based on the strong sensitivity of microwave propagation in order to detect the dielectric changes in a rectangular waveguide moving from the X-band to the K-band. The method is based on the well-known relationship of water content and complex permittivity that causes the dissipative movement of electromagnetic waves through the guide. We obtain a closed-form theory based on Maxwell's equations and the dispersion of the waveguide with a moist sample. We use the transmission coefficient S21 as the sensing parameter. The finite element simulations are then used to validate the analytical formulation and identify the frequency range that is most sensitive to moisture change. We find a dramatic and nearly linear relation between attenuation and moisture content in the 15–20 GHz range and develop a simple affine calibration model for real-time contactless moisture estimation. We show that in comparison to gravimetric and resistive methods the proposed sensor is faster, non-invasive and applicable to a wide range of materials.