A compact quasi-elliptic wideband bandpass filter using series LC-loaded microstrip line

A novel wideband bandpass filter prototype with compact size and sharpened transition has been proposed in this paper. Based on a tight-coupled structure composed of side-coupled series LC-loaded microstrip line, quasi-elliptic wideband filtering characteristics can be obtained easily with wide bandwidth and enhanced skirt roll-off rate by adopting a proper LC load. Detailed theory analysis, electromagnetic simulation and measurement demonstrate that the proposed filter has a number of advantages including low insertion losses, sharp rejection skirts, wide bandwidth as well as its compact size.