When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
Abstract
Microwave filters have been an interesting research topic for more than half a century. Since any communication system is required to use some microwave filters, considerable effort is being made to optimize the performance and size of these filters. As operating frequency is on the rising, filter design becomes more challenging with the demand for low insertion losses and low cost. As low cost might require the use of printed circuit technology, high performance demands waveguide technology that derives the cost to unacceptable levels. There is a need for a new technology that achieves both requirements of low cost and high performance.
The new technology of ridge gap waveguide that was proposed in 2011 shows promising characteristic as a new guiding structure, especially for high-frequency bands. Therefore, it is necessary to design and propose classic or even new filtering devices on this technology. Since ridge gap waveguide is still in its infancy, only a few articles exist in the literature about microwave filters in the ridge gap waveguide. Here, we propose the use of this technology to design practical and efficient microwave filters.
The work of this thesis can be divided into three major parts: (1) Developing efficient codes and methods to optimize the computationally expensive structure of ridge gap waveguide or any other large-scale microwave filter device. (2) Characterizing cavity structures on ridge gap waveguide and using them in the design of simple microwave filters. (3) The third part will discuss more advanced and practical filters, especially using printed ridge gap waveguide technology.
The ultimate goal of this thesis is to design and propose a state of the art designs in the field of microwave filters that can satisfy the requirements of today’s advanced communication systems and to be cost efficient and compete with other rival technologies. Considering the potentials of ridge gap waveguide, we achieved these objectives using efficient optimization, efficient design techniques, and fabrication of the models using advanced technology.