High Power Ka Band Multiplexer

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In response to the growing interest in broadcast services a new frequency band has been allocated in the 17/24 GHz band (17.3-17.7 downlink reverse to current DBS and uplink at 24.75-25.25 GHz). In order to achieve a sufficient power flux density on ground (e.g. for future BSS applications), transponder power levels exceeding 250W up to about 500W are required.

The current technology is limited in power handling and thermal constraints to about 250W for narrow bandwidth applications. This activity addresses the challenges for high power OMUX at Ka Band with narrow channel bandwidths.

The objective is to demonstrate extreme power handling at Ka Band using advanced RF, Mechanical, and Thermal design to build and test a proof of concept output multiplexer. Special consideration is to be given to all aspects of the high power design associated with self-heating, multipaction, corona breakdown and PIM.

Specific interest and attention will be given to critical components of the multiplexer which may pose a limitation to the power handling capability. By means of investigation and verification the manifold, irises and tuning elements will be carefully examined to ensure compliance and margin to the specifications outlined for the activity.


The key issues presented by this project are overwhelmingly related to the power and thermal design. Loss and dissipation generally scale with frequency and channel bandwidth. This activity requires that the boundaries of both be extended. The thermal design is a significant driver of the complete OMUX design effort and tradeoffs will be anticipated at many points.


COMDEV consider the use of the Ka Band spectrum to be an emerging market. Demand for existing spectrum is ever growing and driving the interest in Ka Band. COMDEV consider this activity an opportunity to extend our product offering and verify the performance of novel filter and multiplexer configurations. By conducting these investigations in advance of the market we are afforded the benefit of time. It allows COMDEV to thoroughly scrutinize new technologies and offer our customers a thorough, complete, and compliant product.


Demonstration of the filter and multiplexer concept will be provided by the design, build and test of a 4 channel multiplexer. The channel filters will be 36MHz bandwidth in a contiguous configuration. Channels will be designed and tested up to 500W per channel.

The channel filters themselves will be 4 pole and presented in three configurations demonstrating the flexibility of the design. All filters will be manufactured from aluminium and utilize COMDEV’s thermal compensation mechanism to correct for the thermally induced frequency instability of aluminium cavities.

Multiplexing will be achieved by use of a low expansion manifold material. Careful multiplexer design and the flexibility of the filter allow the manifold length and thermal effect to be muted without additional measures.


The project is divided into three elements.

Element 1 will investigate the OMUX technologies available to COMDEV to fulfil the requirements of the activity. This time will also be utilized to vet the chosen resonator and temperature compensation techniques.

Element 2 will focus on the filter specific design. This time will be spent investigating and designing the filter to withstand the significant RF and thermal demands of operating at 500W power in a fully contiguous condition.

The final phase will focus on the design verification. A multiplexer will be built and tested to verify the operation against the design.

All elements are planned to be complete in 24 months from kickoff. COMDEV have a dedicated R&D department and have allocated resources from that pool to the activity for the duration of the body of work.

Current status

The activity is now complete. COMDEV have executed the contract as intended and the project objectives have been met and exceeded. COMDEV have developed a novel filter concept which exceeded the demands of the requirements. The final delivery demonstrated three variants of the filter concept on a single manifold underlining the flexibility and robustness of the design.

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