Boresight radiation of a dipole antenna with a uniform or non-uniform left handed superstrate

In this paper measurements of the radiation performances of a dipole fed by a coaxial balun and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell are compared. Two types of superstrates, uniform and non-uniform, have been characterised in terms of impedance matching, resonant frequency and gain. First of all the dependence of the impedance matching and resonant frequency with the size of the superstrate has been analysed, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of approximately 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.