Design of a Frequency-Agile and Surface Mountable Suspended Integrated Strip-Line Bandpass Filter Using Castellated Vias

In this paper, a novel method of surface mounting suspended integrated strip-line (SISL) components is designed, and a surface-mount technology (SMT) thru-line is built to demonstrate its feasibility. Additionally, a varactor-based tunable combline filter is designed and fabricated in the same SMT structure to illustrate an application of the technology. A castellated via is used in order to make surface mounting easy and accessible. The design concept is explained, models are provided, and simulated results are shown. The fabricated thru-line and filter are measured, demonstrating the SMT-able technology as well as an S-band tunable filter.