Whispering-Gallery-Mode Microwave Sensing Platform for Oil Quality Control Applications

A growing demand has been established over the recent years for quick and inexpensive oil adulteration detection testing to convoy the automated and computerized processes in the industry. This research study presents a practical application of a simple low-resource microwave sensor of small size and high sensitivity to rapidly identify oil types, and monitor its quality and authenticity without having to open any bottles off-shelf. The sensor utilizes the nonreciprocal whispering-gallery-modes (WGMs) traveling on a ferrite ring resonator (FRR) when coupled to a microstrip line (MTL). The magnetic anisotropy of the ferrite is exploited to acquire four sensitive WGM resonances of nonreciprocal nature in the 22–32-GHz spectrum. A fabricated prototype is practically tested for identifying oil samples of different ingredients and brands, when loaded onto the FRR at consistent volume inside glass bottles of identical geometry. The measured scattering responses have shown a high detection sensitivity for the small contrast between the edible oils as demonstrated by the explicit frequency shifts in magnitude and phase of both S
₂₁
and S
₁₂
. The article also discusses a generalized concept for the complementing system layers in an Internet of Things (IoT) architecture for potential implementation in the industry.