Failure Analysis of Microwave Air Breakdown for the Cavity Filter with Remainder

The microwave breakdown threshold is one of the key factors when consider the power capacity of a cavity filter. In this paper, we analyzed theoretically how the air breaks down between the pin to plate electrodes firstly, and then two essential judgment conditions for breakdown were put forward. One is that the maximum electric field must reach to the breakdown threshold to produce plasma and another is that the average electric field is strong enough to support the charged particle evolve a short stream path between two electrodes. According to two judgment conditions, we made failure analysis of the continuous microwave air breakdown for cavity filter with redundant substance which varying with diameter, length, and rotation angle. It is found that the greater length and smaller diameter the reminder, the formation of breakdown occurs more easily. So, suggestion for quality test standard is concluded that the length of the redundant substance must be smaller than 0.63mm at a 20dBm continuous microwave input.