Dual-mode microwave cavity for fast identification of liquids in bottles

An open metal cavity loaded with a ceramic dielectric resonator and a lumped inductor - capacitor structure allows for simultaneous excitation of the TE_01δ dielectric resonator mode at 2 GHz and a lumped element mode at 100 MHz. The measured quality factors are about 7,000 and 400, respectively. Both modes exhibit strongly overlapping evanescent fields above the aperture outside the cavity. These fields can be used for dielectric and conductivity measurements on liquids stored in non-metallic bottles. The simultaneous use of both modes enables liquid category identification within one second. This method has been successfully applied for bottle scanning in checkpoints.