A Novel Open Drum Shaped Ultrasensitive Permittivity and Permeability Sensor Based on Electric–Magnetic Toroidal Dipole

A novel open drum shaped cavity (ODSC) is employed to estimate the variation of the dielectric and magnetic properties of materials. Compared with the conventional resonant mode excited by normal multipoles, it has the following remarkable property, i.e., concentrating energy. Almost all time-varying electric and magnetic fields are confined inside the ODSC and has high quality factor Q = 573.3. The resonant frequency is ultrasensitive to permittivity and permeability perturbations. The sensitivity is as high as 400 MHz, which is much higher than that in the published literatures. The properties of the target material are estimated by the amount of frequency shift of reflection coefficient S 11. The operation principle of the proposed sensor is initially illustrated by simulations, and then, measurements are performed to show the validity of the proposed procedure. This ultrasensitive sensor can be applied in accurate monitoring variations of permittivity or permeability of liquids, gases, and solids, such as avoiding overuse of cooking oil and qualified dried milk composition.