In this paper, we briefly summarize the theory of transformation optics and introduce its application in achieving
perfect invisibility cloaking. In particular, we theoretically show how the task of realizing cylindrical invisibility
cloaks can be eased by using either structural approximation or material simplification. The corresponding
invisibility performances of the approximate or simplified cylindrical cloaks are presented in detail.
In the present paper, the properties of an antenna centred at a metamaterial slab with zero permittivity are investigated. It
is analyzed that the antenna can achieve high directive performance. Its half power beam width (HPBW) decreases
monotonically with the increase of the width of the slab. While the gain of such antenna can only be 0dB independent of
the slab's width. When the permittivity deviates form zero to a little positive number, antenna can achieve high gain by
choosing appropriate slab's width due to the transmission resonance. The effect of loss is also analyzed.