Cross Coupling in Folded Interdigital Filters using Quarter-Wavelength Resonators with Non-Planar Structures

This work presents cross coupling in non-planar interdigital filters. This design uses shorted quarter-wave resonator in an air cavity structure. The filter structure is folded about one axis to bring non-adjacent resonators closer to each other and introduce cross coupling. The filter is fabricated in the PolyStrata technology. The additive manufacturing of PolyStrata technology allows for high volume, repeatable, low cost filters which scales to sub-THz frequencies. The process is also compatible with industry standard interfaces such as surface mount and wire bonds. As an example, we present a compact E-band diplexer with wire-bondable ground-signal-ground (GSG) interface