Metamaterial Loaded Miniaturized Microstrip Annular Slot Antenna with Increased Gain

In this paper the microstrip annular slot antenna (MASA) loaded with surrounding metamaterial having permittivity and permeability less than zero is investigated with analytical and numerical methods. A solution to the source surrounded by an infinite inhomogeneous medium is obtained. Then the same technique is used to formulate the field equations of the microstrip annular slot antenna (MASA) surrounded by a homogeneous metamaterial. The power gain of the microstrip annular slot antenna (MASA) surrounded by the metamaterial medium relative to the dielectric medium is analyzed and calculated. The analysis of the reactance ratio and the reactive power of the MASA shows that the surrounding metamaterial acts as a natural impedance matching network for an antenna. The equivalent circuit model for the surrounding inhomogeneous medium with metamaterial has been proposed. It justifies the approval of the metamaterial as a natural impedance matching network. The radiated power of the MASA surrounded by metamaterial (with media constant $\varepsilon_{2}=-\varepsilon_{0}, \mu_{2}=-\mu_{0}$) has been increased by 73.66 times the radiated power of the MASA surrounded by a dielectric medium $(\varepsilon_{2}=\varepsilon_{0},\ \mu_{2}=\mu_{0})$.