A 20–26.5-GHz PCB Bandpass Filter Tuned With Contactless Tuners

This letter presents the first substrate integrated waveguide (SIW) k-band filters tuned with contactless printed circuit board (PCB) tuners. Unlike previous efforts, the presented filters exhibit two key advantages that make them particularly attractive with respect to manufacturing, performance, and reliability: 1) they are based on low-cost PCB technology and 2) they employ contactless tuners that exhibit no hard contacts with the evanescent-mode (EVA) cavities they control. A proof-of-concept two-pole prototype with 3.2-3.4 dB loss is experimentally demonstrated in the 20-26.5 GHz band. The fabricated resonators employ a unique contactless tuner geometry that minimizes insertion loss (IL) by utilizing extended cavity sidewalls. This design improves IL by an average of 10 dB in the demonstrated band. This letter also discusses fabrication imperfections and their impact on filter performance.