<i>Ku</i>-Band Reflectionless Single- and Dual-Band Bandpass Filters in Groove Gap Waveguide

Ku-band two-port-reflectionless groove-gap-wave-guide (GGW) sharp-rejection single- and dual-band bandpass filters (BPFs) with close-to-passband transmission zeros (TZs) are presented. The single-band BPF design is firstly introduced, which consists of a balanced circuit topology with the following circuit blocks: 1) a pair of identical riblet-type 3-dB quadrature couplers with isolated ports ended in WR62-interface matched loads and 2) two similar reflective quadruplet-based BPF units. These BPF units with two out-of-band TZs are interconnected between the through and coupled ports of the input<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$/$ </tex-math></inline-formula>output couplers in both circuit arms. In this manner, the overall filtering transfer function is determined by the reflective quadruplet BPF units, whereas their out-of-band RF-signal-power reflections are dissipated by the matched loads. Hence, symmetrical-RF-power-absorption capabilities for the total BPF device are obtained. Subsequently, by applying a split-type single-to-dual-band frequency transformation over the reflective BPF unit, the symmetrical-reflectionless dual-band BPF counterpart is derived. In this case, a vertically stacked scheme for the reflective split-type dual-band BPF unit in the GGW implementation is adopted for higher circuit-size compactness. The RF operational foundations of the conceived two-port-absorptive GGW single- and dual-band BPFs are described. Besides, electromagnetically (EM)-simulated results and sensitivity analyses of their circuit parts for 15.2- and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$14.6\boldsymbol {/}15.2$ </tex-math></inline-formula>-GHz single- and dual-band BPF designs examples, respectively, are shown. Furthermore, to validate the conceived GGW reflectionless single- and dual-band BPF approaches empirically, proof-of-concept prototypes of these designs are manufactured and characterized.