3-D Printed Bandpass Filter Using Conical Posts Interlaced Vertically

A new class of filters using conical post resonators is presented. The proposed structure consists of stacked rectangular cavities where each cavity has a capacitive conical resonating post positioned in its center. The resonator is very similar to that used in combline filters, but in this case, taking advantage of the stacked arrangement and of the conical shape, each post has its upper part partially inserted in the hollow base of the post above it. The resulting structure is more compact than the classical combline filter, whereas the Q-factor is very similar. In order to validate the proposed structure, a doublet filter prototype has been designed, manufactured using additive manufacturing techniques and tested.