Compact Ku-Band OMUX with a high number of channels

Status date
Activity Code
As the telecom satellites become larger and larger the number of channels to be accommodated is increasing steadily. This results
in output multiplexers (OMUX) with a higher number of channels and a larger footprint often together with operating power levels which are still increasing. The ideal output multiplexer has all the properties listed below:
– small footprint
– low mass
– insert positions which do not depend on the multiplexer optimisation or channel centre frequencies or bandwidth, but only on the number of channels required, thus allowing to freeze insert positions at the very beginning of the design phase
– lowest losses for the channel filters and the manifold in order to optimise the electrical performance (low self heating, therefore lower absolute drift) and to minimise the heat flux to be covered by the heat pipes
– all housings, waveguides, baseplate made of aluminium in order to improve the heat flux and to avoid any thermomechanical stress
– all input ports well accessible, sufficient space in order to be able to mount the waveguides without any problems – this is contradictory to the requirement for a minimum footprint.
– Design optimised for good manufacturability and assembling (e.g. Aluminium half shell design) and therefore low cost and reduced delivery time
– all frequency plans within Ku transmit band should be realisable
– channel filter order and filter function type can be chosen individually for each channel (e.g. asymmetrical filter function)
– temperature compensation for the channel filters
– electrical properties of the manifold independent of the temperature
– high power handling capability covering most customers' needs
– low insertion loss, low in band parameter variation, but providing required near band rejection
The output multiplexer proposed here will be designed in order to come as close as possible
to all design goals listed above.
The key issues are:
- Dielectric material with low losses and high thermal conductivity
- Using of dual mode resonator if possible
- Thermal compensation

The increasing number of channels results in output multiplexers (OMUX) with a higher number of channels and a larger footprint. The use of dielectric loaded resonators and/or folding of the manifold will enable a reduction of the footprint. Advances in the understanding of dielectric loaded resonators and the availability of very low loss dielectric material have lead to the introduction of novel dielectric resonator configurations. Very low dissipation losses in the dielectric can now be achieved resulting in acceptable temperatures of the dielectric such that it is feasible to built 120W channel filters in Ku-band. At the same time the dissipation losses are significantly reduced due to the improved resonator Q. Thus, high power dielectric OMUX in Ku-band with at least 25% reduced dissipation losses become feasible with 25% footprint, 50% mass reduction and superior spurious performance in comparison to competing dual-mode TE113 or even lower loss TE114 cavity technology.

In the frame of the project Tesat and KIT develop a compact Ku-Band OMUX with a high number of channels.
The work is divided into two technical phases
The first phase covers the development of the compact high power Ku-Band channel filter. It is dedicated to the material and process selection, electromagnetic design and analysis, fabrication and testing of at least one narrow band and one wideband dielectric high power channel filter BB in Ku-band.
The second phase is dedicated to all RF, mechanical and thermal concept developments for a compact scalable Ku-band higher power dielectric OMUX. Existing temperature compensation techniques for the manifold and resonators will be investigated and further developed to achieve a temperature stable OMUX
configuration. The mechanical, thermal and electromagnetic analysis, design, fabrication and testing of a compact scalable 16 channel Ku-band OMUX channel will be carried out.

The close out of the study will be in 2015.

Current status
The filter CDR was declared successful based on two different concepts. The first concept was based on a single mode cavity loaded with dielectric with permittivity of 10. The second solution was based in a dual mode cavity loaded with dielectric with permittivity of 24. Lately the solutions were re-considered due to the unacceptable high temperature in the Concept 2 and the large dimensions of the Concept 1 design (less market opportunities)
By combining the advantages of both concepts an innovative solution was found which will be followed up in a different program. Therefore the actual program has been stopped at this point.
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