Contents I. Introduction
Microstrip patch antennas have been widely used during the last years because of their good characteristics such as weight, low cost of fabrication, conformity… but their performances suffer from serious drawbacks like narrow bandwidth, leakage due to power supply, relative high cross-polarization and low capacity to handle high power [1]. With the evolution of theory and technology, some of these drawbacks were overcome, or at least attenuated to a certain level [1]. The analysis and design microstrip patch antennas are based on many techniques. The transmission line model and the cavity model techniques are imprecise and limited to only simple and regular shapes of the radiating elements with thin substrates. The spectral domain techniques are widely used in the analysis and conception of microstrip patch antennas of complex forms. The dyadic Green function, which relies tangential electric fields to the current on the surface of the patch is developed [2]. Recently, a big interest was observed in the development and the use of high transition temperature superconducting materials. Many researches have shown that the dissipated power in the millimetric band is very high, especially in the case of a normal conducting material. To decrease the dissipated power and improve the gain, superconducting materials are used. The advantages of using superconducting materials include: small losses which means a reduction in signal attenuation and reduction in noise level; small dispersion up to frequencies of tens of GHZ; miniaturization of the micro-wave devices, which allows a large scale of integration; reduction in propagation time of signals in circuits. Superconducting microstrip patch antennas have a gain relatively greater than the one in the conventional antennas, but they suffer from narrow bandwidths, which limits their applications [3]-[4].
