High-frequency passive components and filters for future high-capacity space and ground communication systems in a hyper-connected world

Abstract

This Ph.D. thesis presents the design and fabrication of microwave filters in microstrip and coaxial technologies. The filters are designed using a novel synthesis technique based on coupled mode theory and inverse scattering techniques, resulting in smooth-profiled filters with improved performance characteristics. These filters are particularly well suited for high-power applications, such as satellite-based communication systems. Satellite RF payloads heavily rely on microwave filters, necessitating robust designs with small footprints and high power handling capabilities for both peak and average power. Traditional filter design methods face limitations when operating across wide frequency bands and achieving sufficient power handling capabilities. The proposed novel synthesis technique offers a general and flexible approach to design smooth-profiled filters, overcoming the drawbacks of conventional design techniques. The core of the novel synthesis technique lies in the coupled mode theory, which characterizes the electromagnetic behavior of non-uniform structures, like smooth-varying microwave filters. The technique involves determining coupling coefficients related to the physical dimensions of the structure through coupled-mode equations. Using this innovative synthesis technique, several smooth-profiled filters are designed in microstrip and coaxial technologies, for different frequency specifications. For microstrip filters, in addition to conventional substrates, non-conventional substrate is also explored. The non-conventional substrate is manufactured layer-by-layer using stereolithography (SLA) with a resin filled with ceramic material. Subsequently, silver nanoparticles are deposited on the ceramic substrate using Aerosol Jet Printing (AJP). The validity of the novel synthesis method and the fabrication technique is thoroughly demonstrated through a comprehensive comparison of theoretical, simulated, and measured results, showing a high degree of agreement between them. Overall, this thesis contributes to the advancement of microwave filter design for satellite communication systems, offering a promising approach to achieve enhanced performance, improved power handling, and reduced manufacturing costs through an innovative synthesis technique and novel fabrication processes.