A PCB Technology-Based 22–42-GHz Quasi-Absorptive Bandstop Filter

A K/Ka-band low-cost continuously tunable quasiabsorptive bandstop filter fabricated with PCB technology is presented for the first time in this letter. A unique implementation of vertically integrated PCB-based evanescent-mode cavity resonator allows the filter to reach a maximum operating frequency of 42 GHz with commercially available linear actuators. The measured results reveal a state-of-the-art performance with less than 1-dB out-of-band insertion loss (1.5-3.2 dB with connectors) and higher than 50-dB isolation. The measured 3-dB bandwidth varies from 1.47% at 22 GHz to 4.65% at 42 GHz. This firstof-its-kind demonstration reveals the high potential of low-cost PCB technologies for manufacturing the high-performance RF front-end filters for high-frequency applications.