Sensing dielectric properties of arbitrarily shaped biological objects with a microwave resonator

A rectangular waveguide resonator operating in the H/sub 107/ mode at 6 GHz was used in determining the change in resonant frequency and the Q-factor of the cavity when loaded with single soybean seeds or corn kernels of various shapes and dimensions. By measuring those variables for a kernel oriented in two positions differing by 90 degrees with respect to the maximum electric field vector, the average values of Delta F (shift of resonant frequency) and Delta T (transmission factor) were found to be virtually shape-independent. The ratio Delta F/ Delta T is a size-independent and well-defined function of the material properties ( epsilon '-1)/ epsilon ", and as such it can be related to the material density, moisture content, or other characteristics when all other properties remain unchanged.<
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