The power handling capability of helical resonator filters is studied by means of the parallel plate model (employed in the European Cooperation for Space Standardisation) and more rigorous modelling techniques (like the one available in the commercial software tool SPARK3D™) as well as through an experimental test campaign. The results indicate that the parallel plate model provides conservative power handling capabilities for this class of filters, while rigorous modelling can better capture the impact of the geometrical features on multipactor evolution. Although the accuracy of the estimated power handling depends on the knowledge of the practical secondary emission yield values, the use of such rigorous modelling tools enables the design of helical resonator filters with improved power handling capability by exploiting the large gap approach, therefore opening opportunities to avoid additional dielectric fillings.

When two filters are cascaded together, unwanted spikes appear in the rejection region. These spikes can have a strong impact on the rejection performance of the resulting filter. Therefore, it is desired to suppress or move them far away from the operational band, including part of the rejection band as well. This paper addresses a systematic evaluation of such phenomenon and proposes a simple yet effective method, called spike envelope curve, to have, in a single run and for any frequency, the worst possible case, without the need of repeating onerous analyses. It is also shown that a judicious choice of the length and losses of the line separating the filters can be exploited to mitigate considerably such a negative effect. The method is assessed by full-wave simulations and measurements.

This contribution presents numerical and experimental results on a 2 nd order UHF filter prototype that exploits helical resonators with modulated radius. Earlier works have proposed this geometry as means to enhance power handling without significantly compromising on unloaded quality factors. Here we present a detailed prototype design and evaluate its performance at low and high power levels using both rigorous numerical tools as well as the results of an experimental test campaign. Low power results include CST predictions against measurements on a Vector Network Analyser. High power results include predictions from the tool SPARK3D as well as the outcome of a test campaign at the ESA-VSC laboratories. Despite some discrepancies in the power handling predictions, which are largely attributed to uncertainties associated with prototyping, the presented results indicate that there is margin for significant performance improvement by adopting the large gap approach for this class of filters.

This paper presents an efficient segmentation of a filter made up of cylindrical multimodal cavities, coupled side by side, that leads to a reduced-complexity model. The latter is built by the combination of the Generalized Reactance Matrices of only two parallel cylindrical waveguides coupled through an aperture which the filter is segmented in. This allows to build the databases necessary for the optimization considering one coupling aperture at a time, thus reducing drastically the computation effort.

The design of a space qualifiable tunable Ku-band bandpass channel filter is presented. The filter is able to be reconfigured once in orbit in terms of both center frequency (150 MHz approx.) and bandwidth (36/54/72 MHz). In order to match the performance characteristics of current state-of-the-art IMUX channel filter technology, in terms of Q-factor, amplitude/phase flatness and size/mass, dielectric resonator technology is employed. The actuation mechanism, composed by two (space-qualified) actuators and two displacement sensors per channel, is such as to deliver the positioning accuracy needed with very low power consumption (zero while in hold). The design, that accounts for the on-board environmental conditions and constrains such as temperature variation, microvibration and EMC rules, is supported by bread-boarding activities performed for both the RF and mechanical concepts.