Study on Multipactor Breakdown in Coaxial to Microstrip Transitions

The objective of this paper is to study multipactor breakdown in coaxial to microstrip transitions. This kind of transitions generally exhibit a gap just below the central pin of the coaxial connector. This gap can create a region where the electric fields are relatively strong so that an electron path may be created that could potentially lead to a multipactor breakdown. In this paper, we study the multipactor modes which may be induced as a function of structural parameters, such as the substrate thickness and the gap length. In particular, it is found that two kinds of electron trajectory can be created leading to critical power levels that are even lower than those obtained with the parallel-plate model, generally used as a conservative model. In this context, we demonstrate that multipactor breakdown can happen for input power levels lower than 500 W. This, in turn, may become a critical issue for the use of classic coaxial to microstrip transitions in new high power satellites whenever payloads are manufactured using planar technology.