High Power SMA Connectors

On board of satellites traditionally Travelling Wave Tube Amplifiers (TWTAs) together with standard waveguide technology were used for transmitters in telecommunication payload systems. With the advent of Solid State Power Amplifiers (SSPAs) printed circuit board (PCB) technology became also attractive for the output stages of these high-power transmitters with the advantage of smaller size, lower weight and higher integration density. In a power combining circuitry the PCBs have to be interconnected by phase stable coaxial cable assemblies with suited connectors. Although SMA RF connectors are preferred in space telecom missions because of their light weight and small size this type of connector has serious limitations in terms of the required RF power handling. Therefore in these high power sections, one is still forced to use the often bulky TNC connectors. Under the ESA activity ”High Power SMA Connectors” a European consortium has been created for the investigation of small size high power coaxial connectors that will be optimized with regard to RF-breakdown, Corona, Multipactor and PIM effects as well as thermal power dissipation making them applicable in satellite transmitter stages. The goal is the development of a new family of high power SMA connectors capable to withstand power levels of at least 50W CW in space environment to match the levels delivered by the new generation of Solid State Power Amplifiers. The research is manifold: First, suitable theories of PIM, corona discharge und multipactor in coaxial structures have to be established or adapted from known similar (waveguide) problems. Second, the power limiting effects in SMA connectors like the internal air gap have to be identified and eliminated by appropriate changes of the connector design. Third, suitable materials for the individual parts and the manufacturing process of the new high power SMA connectors have to be analysed and selected. The activity started with a deep literature research of the state of the art of the interesting phenomena followed by first suggestions of the basic design of a high power SMA connector. At the workshop we will report on the status of the project and on the achieved results.