Sensitivity considerations for inline fully canonical filters at ku-band

In this paper, a planar inline fully-canonical topology is proposed to reduce sensitivity to fabrication tolerances compared to conventional inline all-pole configurations. Major concerns are related with errors in the absolute positioning of via-holes to ground which affect inter-resonator (main-line) couplings. The total expanded sensitivity considering variations of the main-line couplings have been obtained for fully and non-fully canonical configurations. The result shows that sensitivity is lower in the case of fully-canonical topologies. Moreover, the allocation of the transmission zeros plays a key role in terms of sensitivity. A prototype has been designed for the Ku-band based on asymmetrical coupled lines obtaining IL = −1.6dB,RLbelow−18 dB, and out-of-band rejection higher than −50 dB.