Abstract: A sensor and method for identifying the surface properties of a workpiece includes a microstrip sensor for transmitting and receiving microwave signals and surface properties determining means for determining the surface properties of the workpiece, including the type of material from which the workpiece is constructed, based upon the strength of the detected microwave signals. The surface properties identifying sensor also includes a microwave generator for producing microwave signals at a predetermined frequency for transmission by the microstrip sensor and a detector for detecting the microwave signals received by the microstrip sensor from the workpiece. Thus, workpieces comprised of a conductive material, an insulative material and a conductive material coated with a radar absorbing material can be readily distinguished by the surface properties identifying sensor and method.

Abstract: In a microwave drying cavity, a thermal radiator provides infrared radiation that complements the microwave radiation in effecting a more uniform drying of a product within the cavity. The radiator includes a metal plate having apertures of a trifoliate configuration and electrical resistance-type heaters embedded in the plate. The trifoliate apertures permit microwave radiation of universal polarization to pass through the plate, so the radiator may be placed close to the product without shielding the product from the microwave radiation.