Abstract

Among state-of-the-art guiding structures, the Ridge Gap Waveguide (RGW) is a promising technology, as it minimizes the losses in high-frequency applications and supports wide operating bandwidth. There is another form of the guiding structures that utilize the idea of the Artificial Magnetic Conductor (AMC) surfaces such as Groove Gap Waveguide (GGWG). It has the same advantages as the RGW in terms of losses, and immunity to leakages without the need for electrical contacts, but with different dispersion characteristics. The RGW supports a quasi-TEM mode while the GGWG supports TE modes as it's a different form of the rectangular waveguide. Therefore, GGWG has high power capability comparable to the standard waveguides. As currently, interest is increasing of millimeter wave and microwave applications, the RGW and GGWG are excellent candidates for these applications due to their low loss. It is quite essential to develop microwave components with superior electrical characteristics for such applications.

The anisotropic materials have useful physical properties that can benefit the microwave devices, due to their enormous advantages such as high stability and wide bandwidth in the millimeter wave band. Ferrite is an example of such anisotropic materials. Their properties can be deployed to improve the performance of the millimeter microwave devices in terms of higher stability, wider band, and high power handling.

Taking advantages of the above characteristics, the research work in this thesis is focusing on their use for microwave and millimeter wave frequencies. The presented devices are responsible for the feeding of the antenna systems. Moreover, they can be deployed in different applications such as antenna beamforming. In this thesis, the differential phase shifters and the orthomode transducers (OMTs) are realized by different technologies that are suitable for both of the microwave and the millimeter wave bands that serve different applications of the wireless communication systems.

The research work done can also be summarized in two parts. The first part starts with the study and investigation of the ferrite material properties and their role in the microwave devices. Then, later providing a new accurate model with mathematical formulas for the differential ferrite phase shifter. Moreover, a new design methodology for those phase shifters is presented. Later, the ferrite is applied in the conventional waveguide, Substrate Integrated Waveguide (SIW), and RGW technologies.

In the second part, study, design, and analysis of different types of the orthomode transducers are presented. They are devices responsible for combining and separation of two orthogonal polarizations. The presented OMTs has a compact size with excellent performance. Several OMT types are considered such as the one-fold symmetry, asymmetric, and two-fold symmetry. The first mentioned two OMTs are realized by deploying the waveguide technology, while the two-fold symmetry OMT is based on the GGWG technology. It has the ability to design a feeding network for an array of antennas based on the GGWG technology. Moreover, this OMT is fabricated using 3D printed technology that uses the carbonated plastic material, in which two copper layers are covering all the structure surfaces by electroplating. This fabrication is a new promising technology that is not expensive, lightweight and less complex than traditional machining. However, there are some concerns about power handling and high temperature withstanding. Such problems might have a solution in the future with a more accurate 3D metallic printers.