Metal plate lens in a focused beam system for microwave material testing

This paper reports an investigation of metal plate lens behavior in the Fresnel region and, in particular, its beam-shaping capabilities. Both numerical modeling and measured results demonstrate a "stripe" beam, as predicted. The beam focusing was demonstrated experimentally by comparing the field produced by each component. Both the metal plate lens and the dielectric lens produce higher field amplitudes at the focus compared to the feeding horn-lens system. In addition, both have a flat phase characteristic over the beam waist. Compared to the dielectric lens, the metal plate lens is very simple to design and manufacture. However, the dielectric lens is more efficient and offers larger bandwidth.