Microwave foreign object detector for detecting foreign matter tobacco, incorporates line resonator intensifying energy density within test zone

摘要

A microwave resonator monitors a conveyor-borne supply of tobacco (3) particles. The resonator has a housing (4.1-4.5) with a flow (3) passage (10) where it is exposed to microwaves. The resonator has especially a line resonator (21) with an end-face (20) which intensifies the energy density of the electromagnetic waves within some or all of the test zone. The assembly has a coupling antenna (17) and a de-coupling antenna (18). The resonator (21) has a cavity (7) defined by walls. The resonator end-face is located in the immediate vicinity of the testing zone (3). The resonator end-face (20) is parallel to and smaller than the cross-sectional area of the testing zone. The resonator is a metal strip whose end-face is directed to the test zone. An Independent claim is also included for a testing process in which cut tobacco is simultaneously subject to examination by two or three resonator probes. The resonator probes point in different directions.