Computer Aided Design of Microwave Front-End Components and Antennas for Ultrawideband Systems

This dissertation contributes to the development of novel designs, and implementation techniques for microwave front-end components and packaging employing both transmission line theory and classical circuit theory. For compact realization, all the presented components have been implemented using planar microstrip technology.;Recently, there has been an increase in the demand for compact microwave front-ends which exhibit advanced functions. Under this trend, the development of multiband front-end components such as antennas with multiple band-notches, dual-band microwave filters, and high-Q reconfigurable filters play a pivotal role for more convenient and compact products. Therefore, the content of this dissertation is composed of three parts. The first part focuses on packaging as an essential process in RF/microwave integration that is used to mitigate unwanted radiations or crosstalk due to the connection traces. In printed circuit board (PCB) interconnects, crosstalk reduction has been achieved by adding a guard trace with/without vias or stitching capacitors that control the coupling between the traces. In this research, a new signal trace configuration to reduce crosstalk without adding additional components or guard traces is introduced.;The second part of this dissertation considers the inherent challenges in the design of multiple-band notched ultrawideband antennas that include the integration of multilayer antennas with RF front-ends and the realization of compact size antennas. In this work, a compact UWB antenna with quad band-notched frequency characteristics was designed, fabricated, and tested demonstrating the desired performance. The third part discusses the design of single- and dual-band dual-mode filters exhibiting both symmetric and asymmetric transfer characteristics. In dual-mode filters, the numbers of resonators that determine the order of a filter are reduced by half while maintaining the performance of the actual filter order. Here, in order to maintain high performance of conventional rectangular waveguides in planar form, substrate integrated waveguide (SIW) technology was utilized. A design of single-band dual-mode SIW filters with improved upper stopband performance and a design of dual-band dual mode SIW filters are introduced. Compact evanescent-mode SIW filters are also realized for low frequency applications and for better stopband performance. In addition, a novel tuning solution for planar SIW reconfigurable filters is also presented. Tunablity of the reconfigurable filter is achieved by adjusting dc-magnetic bias applied to the ferrite material. The new tuning technique leads to a dramatic reduction in complexity for the external control system.