Design and implementation of dielectric resonator based metamaterials

In this thesis, a metamaterial structure based on an array of dielectric resonators is designed and implemented in waveguides. In the first part of this thesis, the metamaterial characteristics of an array containing dielectric resonators is demonstrated by evaluating the permittivity and permeability of the array structure in rectangular waveguide and parallel-plate waveguide at X-band. The scattering parameters in both structures are obtained with CST Microwave Studio simulations and supported with measurement results. Then, the effective relative permittivity and permeability values are extracted with the de-embedding technique and retrieval method, and the frequencies at which the structures possess both negative permeability and negative permittivity simultaneously are shown. It is shown that the array with dielectric resonators has metamaterial characteristics at certain frequency bands. In addition, these certain frequencies of both structures are found to be consistent to each other. This means that the metamaterial behaviour of the dielectric resonator array is highly insensitive to the wave excitation. In the second part of the thesis, an implementation of the metamaterial structure is used in a waveguide directional coupler. For this purpose, a four-hole waveguide directional coupler in X-band is designed. Then, the block of dielectric-resonator array is inserted between isolation port and holes of the coupler, and the performances of the coupler with and without dielectric resonators are compared in terms of the coupling and isolation. The obtained results show that the coupler with dielectric resonators significantly improves the coupling and isolation performances at a new operation frequency band at which the traditional coupler does not work. Therefore, the metamaterial structure attains multi-band characteristics to the coupler. Besides, this new frequency band can be shifted by arranging the distance between the dielectric resonators and holes. Finally, it is also observed that the bandwidth of the new frequency band can be increased by using more dielectric resonators in the array.