Use of metamaterials on antennas and reflectors

The common classical method that is used to improve the directivity gain of microstrip patch antennas, which are frequently used in wireless and mobile communication systems, is to design the array antennas. But the main two disadvantages of this method are; coupling between each element and the feeding of each antenna. This thesis proposes using of a separate superstrate metamaterial (MM) lens layer to enhance the directivity gain of the microstrip patch antenna in the Ku Band (12 GHz). Initially, a microstrip patch antenna is designed at Ku-Band. Later, the unit cell structures of the metamaterials are designed and scaled to show the metamaterial characterization in the Ku band. Furthermore, the geometric details on the unit cells of the metamaterials leading to the inductive and capacitive effects, is investigated. Є and μ curves of the unit cells are plotted in MATLAB by utilizing the Robust method to verify that both media parameters (є,μ) are negative at Ku band. In order to convert the unit cell metamaterial structures into a periodic lens layer, the optimal distribution in the dielectric layer, the optimum distance to the reference antenna and the optimum angle with the incident wave are determined and the five different metamaterial lenses are used according to these values. Simulations and designs are carried out in CST, and production and laboratory measurements are carried out in the RF and Microwave Laboratory of Electronics and Communication Department at Yıldız Technical University. It has been observed that the measurement results are close to computer simulations and that in both cases there is an improvement in the reference antenna directivity gain. In addition, parallel to the increase in the directivity gain of the reference antenna, the HPBW is also found to be decreasing as an evidence of increase in the directivity. Finally, an offset horn feed parabolic reflector antenna operating at 29.75 GHz Ka band transmitter frequency, is designed, simulated and the directivity radiation pattern is plotted. Then an omega MM lens layer is designed to show DNG characteristic in the same frequency range and used inside the horn antenna and the far field radiation pattern was replotted. According to the simulation results, when the MM lens is used, an increase of +3.7 dB in the directivity and a 4.3 ° decrease in the HPBW of the feed horn antenna, is observed.