Radiation of a rectangular microstrip patch antenna covered with a dielectric layer

The effect of a protecting dielectric superstrate on the radiation pattern of a rectangular microstrip patch antenna is investigated theoretically. The analysis approach is based on the spectral-domain method of moments in conjunction with the stationary phase method. A new concise expression is derived for computing the radiation electric field. The validity of the solution is tested by comparing the computed results with the experimental data. At higher superstrate thicknesses, numerical results indicate that the radiation pattern drastically changes into three lobes. The resonant frequency, on the other hand, increases with the increase of the thickness of the dielectric cover.