Miniaturized Tri-Band Bandpass Filters Based on Multi-Mode Resonators with Pseudo-Interdigital Structure

Abstract

Based on open stub-loaded dual- and tri-mode resonators, two miniaturized microstrip tri-band bandpass filters with good performance are presented. A pseudo-interdigital structure is introduced to realize size reduction. The 0° feed network is applied to create at least one transmission zero near the passband edge of each passband, resulting in high rejection and selectivity. The mode-splitting technique is used by combining two multi-mode resonators with electrical coupling, and the split two modes generate one passband. For demonstration, two tri-band bandpass filters with dual- and tri-mode resonators are implemented, respectively. The simulated and measured results are presented and show good agreement.

Keywords:

• tri-band bandpass filter
• multi-mode resonator
• mode splitting
• pseudo-interdigital structure

Additional information

Funding

This work was supported in part by the Ministry of Science and Technology of the People’s Republic of China (grant 2013YQ200503).