The Use of Quarter-Wave Resonators to Improve Modal Filters Performance

The paper presents the results of a quasi-static analysis of the two-conductor and the four-layer reflection-symmetric modal filters with and without the quarter-wave resonators. The use of resonators can improve electrical properties of the devices based on modal filtering. The authors performed simulations in the time and frequency domains taking into account the losses. The geometrical parameters of the quarter-wave resonators were optimized using a genetic algorithm. The results show that the presence of the quarter-wave resonators improves interference suppression. Thus, the attenuation of more than 60 dB in a wide frequency range was achieved for the two-conductor modal filter. For the four-layer reflection-symmetric modal filter, the attenuation of 25 dB was obtained. The results of the time domain analysis demonstrate that the proposed configurations suppress ultra-wideband electromagnetic interference better than the configurations without resonators.