Calculation of a low Q value, coaxial output cavity

The low Q value coaxial output-cavity with large coupling holes is often used in the high power microwave devices. The structure of this cavity is of three dimensions with traveling wave boundary, and it is very difficult to calculate its high frequency characteristics by methods of lumped parameters and numerical. On this condition, a new kind of analytical methods is developed in this paper. According to the equivalent principle of field, the cavity is divided into five regular regions. The field in each region is excited by proper surface magnetic current density on the common interface and it can be expressed as integral of Green functions. The magnetic fields of two adjacent regions are then matched on the common interface to obtain a set of integral equations. From the integral equations, the resonant frequency of the cavity and the magnetic current density can be solved. The coaxial output cavity is also calculated by Mafia code. The calculating results are matched well with the experiment.