Microwave system for moisture mapping by a linear array of slot sensors

Abstract

A linear array of microwave sensors for moisture content mapping in thin or thick material sheets is introduced. The array building block is represented by a straight microstrip line electromagnetically coupled to a resonant slot structure properly loaded by two PIN diodes. Each array element constitutes a single slot sensor interacting with the material under test by means of the fields radiated through the slot. When the diodes are in the ON state, each sensor and, thus, the whole array, acts like a low loss transmission line. Otherwise, when the diodes are in the OFF state, the slots are allowed to resonate. Switching the array elements one at a time, the array electronically scans the specimen under test.