New design techniques for telecommunication payloads of space systems suitable for additive manufacturing in the context of large platforms

Abstract

In this thesis, microwave filters capable of handling high-power designed using novel synthesis method based on coupled-mode theory and inverse scattering technique and fabricated using metal additive manufacturing (AM) is presented with a view for space-based satellite applications. Microwave filter is one of the key components in a satellite payload system and as such its design and engineering requires careful consideration of various factors such as frequency range, size, weight, and power consumption limitations. The filters designed using classical methods usually suffer when operating in a wide frequency band and have low power handling capability. Thus, in this thesis, the novel synthesis technique which is general and flexible for any passive and causal frequency response is used to design filters having smooth-profile, which provides the advantage of supporting high-power. Such complex structures cannot be easily fabricated using traditional CNC methods and if done will require more time which increases the overall manufacturing cost. Thus, the smooth-profile variation of the filters is also orientated such that it is suitable to be fabricated using additive manufacturing in metal with ease. The coupled-mode theory, on which the synthesis technique is based, is used to characterise the electromagnetic behaviour of a non-uniform structure, such as a smooth-varying microwave filter, in terms of its coupling coefficients which is related through the coupled-mode equations to the physical dimensions of the structure. On the other hand, the inverse scattering technique, such as integral layer peeling method, is used to calculate the coupling coefficients from the target frequency response. Once designed, the filters are fabricated using Selective Laser Melting (SLM) technique which is one of the most commonly used metal-based AM technology. Various prototypes of the microwave filters, in both rectangular waveguide and microstrip technology, in different frequency range are considered and the results of their synthesis and fabrication are compared and analysed with the theoretical background where a high degree of agreement between them suggests the validity of the novel synthesis method and the fabrication technique.