Miniature Dual-Mode Microstrip Bandpass Filters with Enhanced Parasitic Coupling

We report the results of an investigation into dual-mode operation of microstrip loop resonator based on meander slow wave structure, and its applications for designing miniature dual-mode bandpass filters. A new feed arrangement for the miniature dual-mode filters is also proposed and investigated in detail. The feed arrangement supports the proposed enhanced coupling between I/O ports of the filter. Both calculated and measured results for two-pole and four-pole dual-mode filters are presented.