Microwave moisture sensing via waveguide with slot array

摘要

An apparatus, for sensing the permittivity of a material is provided. The apparatus includes a waveguide (1) which has a linear array of slots (2) and a generator (6) which generates one or more microwave signals, where the microwave signals are directed to the waveguide (1). A measuring means (5) is also provided to determine a scattering parameter or equivalent for either transmission direction of the waveguide (1) in response to said one or more microwave signals. In use the scattering parameter or equivalent indicates the permittivity of the material by averaging measurements obtained in both transmission directions of the waveguide (1).