Accurate resonance frequency detection in a microwave moisture measurement

摘要

This paper describes a technique for accurate resonance frequency detection of a moisture measurement system using a dielectric ring resonator operating at a center frequency of about 2.1 GHz by eliminating the influence of noise superim- posing on the resonant curve. The curve fitting midpoint method is the most effective one among the three methods examined in this study. The cardboard samples with about 5 to 115/100 moisture on a dry basis were measured using the curve fitting midpoint method. The standard deviation of the predicted moisture contents is 1.14/100(d.b.)over the whole range of moisture contents measured.