Recent communication satellites are designed to cater to a constantly increasing number of users, thus demanding increasingly higher bit rates. This combination implies increasing power levels of RF equipment downstream from the power amplifiers to the OMUXs. In this situation, different discharge phenomena such as multipactor may occur inside the microwave devices, limiting the transmit power of the satellite. Multipactor suppression techniques such as surface treatment tend to degrade with time, and surface geometry modification can be a very complex operation. Due to these limitations, this work investigated, via a mathematical model, the possibility of using a DC magnetic field to effect suppression of multipaction with particular emphasis on waveguides with rectangular geometry. The result of the analysis and simulations of the model using MATLAB and MS Excel Spreadsheet applications suggested that a small magnitude DC magnetic field perpendicular to the electric field and in the wave propagation direction is effective in reducing multipaction.

Microwave breakdown discharge phenomenon has continued to gain significant research efforts because of the limit it places on the power-handling capacity of satellite RF equipment and particle accelerators (Puech et al., 2003; Arregui et al., 2011; and Pérez et al., 2011). This paper follows earlier works on the same subject of multipactor suppression using DC magnetic field presented at the 2nd International Conference on Computer and Automation Engineering (ICCAE-IEEE, 2010) and the 3rd International Conference on Advanced Computer Theory and Engineering (ICACTE-IEEE, 2010). Wachowski (1964), explaining the multipacting process, stated that multipactor breakdown starts with the assumption that there are a few free electrons present in a waveguide filled with gas at a low pressure. Under the influence of the applied RF electric field, electrons cross the guide without colliding with a gas molecule. Upon striking the waveguide wall, secondary electrons are emitted. For most materials, the secondary emission yield becomes greater than unity if the impact energy of the incident electrons is sufficiently high. If the transit time of an electron across the guide is any odd multiple of a half-period of an RF cycle, then the number of electrons crossing back and forth in synchronism with the applied RF field increases very rapidly in avalanche fashion. Further transmission of RF energy is disrupted as a result. The consequences of this breakdown include damage to satellite microwave equipment, link budget degradation, and generation of excess heat which can lead to melting and cracking of components, increased noise generation, harmonic distortion and inter-modulation (when multiple frequency RF signals are applied) and general degradation in payload performance. Current conventional multipaction suppression techniques have showed limitations in effectiveness (Proch et al., 1996). Related work on the subject by Geng and Padamsee (1999) was limited to the assumption that electron emission velocities were perpendicular to the emission surface. In reality, electrons are emitted at random angles. The suppression model presented in this work took this random emission into full consideration.

Electrical and Electronics Engineering Journal, Microwave discharges, Multipactor breakdown, Rectangular waveguide,
Secondary emission.