Wideband 3-D-Printed Coaxial-Line Filters for SatCom Applications

In this paper, we present the latest advancements in the development of 3-D-printed, self-supported air-filled coaxial-line filters. The filters are intended for satellite communication (SatCom) systems, where they must effectively reject signals in a wide frequency range. Each filter design incorporates a low-pass filter (LPF) structure, integrated with a short bandpass filter (BPF) section. Two filters are presented, differing in the design of the BPF part. In the first design, the bandpass section is composed of four short-circuited linear stubs and provides a passband located at X-band (8-12 GHz). The second design employs specially shaped conical, radial stubs, aiming for a more wideband behavior (with fractional bandwidth (FBW) reaching 80%). In order to suppress the third harmonic and other undesired out-of-band frequencies, both designs utilize a smooth-profile low-pass structure which provides a wide rejection band up to around 40 GHz, in line with the requirements of the target application. Several prototypes were fabricated in one piece in aluminum alloy using selective laser melting (SLM) and measured, exhibiting excellent agreement with simulations, thus validating both design concepts.