Monitoring of water/ice state using millimeter waves for the agricultural field

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Monitoring of water/ice state using millimeter waves for the agricultural field

Ogawa, Y. / Shindo, K. / Mizuno, M. / Otani, C. / Kawase, K.

In this research, we have built an experimental setup for measuring the water content in plants or food material, and for determining the water/ice state of a sample, as an application of millimeter waves in the agricultural field. Our measurement system for water content is based on a 35 GHz Gunn oscillator. We have checked that the absorption of a leaf is directly proportional with its water content; consequently, we suggested a nondestructive technique for monitoring the leaf moisture level by measuring its transmission in the millimeter wave region. This method can be applied in agriculture for monitoring the plant growing process. Identically, the water content in sesame seeds was measured in a reflection configuration. Additionally, a possible industrial application was suggested. Another direction of research consists in discriminating between the liquid state and the solid state of water. The difference in absorption coefficients for water and ice in the millimeter range is significant (ice absorbs three order of magnitude less than water), which allows the detection and monitoring of the water/ice state in a series of applications.