Characterizing wood by microwaves

Common properties of raw wood can be determined by measuring the microwave propagation in the media. Unlike early designs from the 1970s and 1980s, simple constructions with phase and attenuation recording are now possible, if optimal frequencies are selected. At K-band, most quality impairments can be detected from basic group delay measurements, e.g., knots or insect holes smaller than 5 mm are observable. Impairments can be detected from a non-parallel viewing direction.