Multimode Dielectric Waveguide Ring Resonator for Radar-Based Real-Time Emulsion Monitoring

Water-in-oil emulsions pose major challenges in areas as chemical- or offshore-systems, where droplet coalescence leads to blockage, corrosion, and equipment damage. Conventional monitoring depends on time- and cost-intensive laboratory analysis. This work introduces a multimode dielectric waveguide ring resonator combined with an extended D-band (126-182 GHz) FMCW radar for in-process emulsion destabilization monitoring. The key is a symmetric dual-coupling design that selectively excites ten even azimuthal modes with 6 GHz spacing, enabling robust, redundant sensing. Electromagnetic simulations and VNA measurements validate the resonator behavior. During coalescence, a 280 MHz frequency shift is measured, consistent with Boyle’s permittivity model. The radar-based sensor demonstrates high sensitivity and practical suitability for real-time industrial monitoring.