  Focal-plane imaging with microwave and millimeter wave has many potential
applications. The bad resolution is a main shortcoming of this technique at
present. In this paper, influence of frequency of electromagnetic wave on the
refractive energy is analyzed. According to the refractive mechanism of
electromagnetic induction, the principle for designing artificial materials
with enough refractive ability is proposed. The material of artificial
molecules is fabricated with cage-shaped granules of conductor (CGC). The
refractive index of CGC material to microwave was measured by assembling CGC
prism with PS (polystyrene) prism or SGC (solid granule of conductor) prism.
The assemblies greatly eliminate displacement of the outgoing microwave caused
by diffraction. This is a key point to achieve direct measurement of the
refractive index under the microwave. CGC material shows a considerable
refractive ability. SGC material and PS show little refractive ability. The
results are useful in promoting image technique of microwave and
millimeter-wave by improving the refractive ability and eliminating detriment
of the diffraction on the lenses.
