New achievements and configurations of helical resonator filters for space applications - theory and design
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The satellite for communication uses frequencies from UHF band (300MHz to 3 GHz) up to Ka band (40GHz). The dimensions of the components in the satellite transponder, usually decrease with the frequency increment. For the Ka band typical dimensions of the microwave components are in the order of 10mm while for lower frequencies such as UHF band, the dimensions are in the order of 100mm. For this last case, there is the necessity of the reduction of the size of the component to save mass and minimize the footprint in the satellite transponders. This work focuses on the filters that compose the input and output multiplexer (IMUX and OMUX) for the UHF band applications. In particular, the OMUX manage several hundred of watts of RF power, so, in this case, the filters has to be designed for high power, maintaining the small dimensions and low mass. In the thesis, prototypes waveguide filters loaded by single helical resonator were designed and manufactured. The prototypes were tested for high power in ESA-VSC High Power RF Laboratory in Valencia to verify their power handling characteristics. For the IMUX, the thesis concentrates on the mass and dimensions saving due to the fact that, for UHF band, typical size of waveguide filters is higher than 100mm. the proposed solution is to use a dual mode concentric helices filters. The novelty of this kind of solution required the development of the mathematical background for the first dimensioning and analysis of filter characteristics. All the theory developed is reported in this work. The output of this procedure is the design and simulation of a very compact dual mode concentric helices filter (28.08mmx28.08mmx10.36mm). A prototype is produced using 3D additive manufacturing technique and the test campaign is in progress. In conclusion, for the helical resonator filter in OMUX, the high power test confirms that this technology is promising for power handling purposes and gives some suggestions for future development such as changing the helix geometry and loading the helices with dielectrics. For the dual mode concentric helices filter, the hope is that the test campaign will confirm the designed results and after, the possible next step is to improve the design for high power applications.