EM-based Design Approach for Multiband Filters by Reflected Group Delay Method and Cascade Space Mapping

In this paper, an EM-based design approach for designing multi-band filter is proposed. In this method, N multiband resonant units with M resonating nodes (or an M mode resonator) are cascaded to create an N-pole and M-band filter response. Each unit is sequentially designed using the reflected group delay method and cascade space mapping technique. It also provides an efficient approach to reconfiguring a bandpass filter into a multiband filter by adding resonant node to main line resonators to form multiband resonant units. To validate the proposed method, a dual-band filter and tri-band filter are designed in Sonnet em simulator, fabricated and tested. The proposed method results in reliable performance and very good isolations between passbands.