Ultra-Compact Inkjet-Printed Folded Waveguide Resonator-Based Bandpass Filters

A concept to develop ultra-compact self-packaged 3D waveguide bandpass filter (BPF) is reported. It is based on inkjet-printed 3D folded-waveguide resonators. Size compactness is achieved using: i) a miniaturized waveguide resonator geometry and ii) monolithic integration by employing a two-material piezo drop-on-demand process. The operating principles of the folded-waveguide resonator concept are presented using eigenmode simulations while taking into consideration the process manufacturing capabilities. The applicability of the folded waveguide resonator concept to highly-miniaturized monolithic BPF is explored through the design and manufacturing of a second-order BPF that exhibits: i) a passband centred at 10.73 GHz with minimum in-band insertion loss (IL) of 2.65 dB and a 3 dB fractional bandwidth (FBW) of 21.6%. Furthermore, it occupies an ultra-compact volume of only 0.34λ₀ x 1.26λ₀ x 0.16λ₀ and only weighs 1.16 g.