The near-field microwave focusing in the layer mediums

This paper deals with the microwave focusing in the layer mediums near the antenna aperture. Based on the plane-wave spectrum theory, the relationship between the Hertz potential and the electromagnetic field is discussed. An approach to the description of the field distribution in the layer mediums in case of an arbitary field source is proposed. Given the focusing current distribution over the antenna aperture, the field distribution of the focal region is worked out. In describing the field distribution over the focal region, the integration of spectrum functions in the spectrum domain (k
x
, k
y
) is carried out instead of the complicated Fresnel integral. The approximations are obtained by the saddle-point integration. Comparison with experimental results demonstrates the validity of the approach.