Enhancement of corona discharge thresholds in microstrip bandpass filters by using cover-ended resonators

This paper studies the corona discharge power thresholds in microstrip bandpass filters (BPFs) and, in particular, is focused on a solution based on lambda/2 cover-ended resonators to enhance their peak power handling capability (PPHC). First, a parametric analysis is carried out to evaluate the variation of the maximum electric field and the unloaded quality factor (Q(u)) as a function of the cover's geometrical dimensions (i.e. height, length, and width). Next, several microstrip BPFs centered at 1.6 GHz are designed, and their behaviors under moderate-to-high applied RF power signals are simulated to corroborate the previous study. A suitable number and size of covers are selected to enhance PPHC without barely degrading the filters' electrical performance and, consequently, without hardly increasing the insertion losses. Finally, two third-order filters with covers and without covers (benchmark prototype) are manufactured, by way of illustration, and they are tested in the European High-Power RF Space Laboratory to validate the good performance of the proposed solution, where a PPHC enhancement of 3.1 dB at high pressures is achieved as compared to the benchmark prototype.