A Millimeter Wave System for The Analysis of Logs

The measurement resolution of the internal structure of logs and sawn timber can be enhanced by using the transmission and reflection of Ka-band millimeter wave energy injected with a selected polarization into the test samples. Particularly, the size, number and location of knots and other similar defects e.g. due to insects can be recorded in nearly real time with a spatial resolution of 1 mm and a positioning accuracy of 3 mm. Most sensitive test parameters are phase changes up to several hundred degrees and attenuation dips of 10 - 30 dB. The base attenuation in dry knot-free timber is typically 300-700 dB/m. Thus, with an output power of 0 dBm, samples having a diameter of 200 mm or less can be measured. A simultaneous recording of reflection can reduce errors caused by non-significant surface deformations.