Low-Loss Air-Filled Substrate Integrated Waveguide (SIW) Band-Pass Filter with Inductive Posts

A low-loss band-pass filter made of inductive posts and based on air-filled Substrate Integrated Waveguide (SIW) is proposed in this work. It is implemented on a low-cost multilayer printed circuit board (PCB) process. The top and bottom layers may make use of an extremely low-cost standard substrate such as FR-4 on which base-band or digital circuits can be designed so to obtain a very compact, high performance, low cost and self-packaged integrated system. For measurement purpose, an optimized-length Ka-band dielectric-to-air-filled SIW transition with 0.23 +/- 0.06 dB insertion loss and a TRL calibration kit are introduced. The design of the proposed band-pass filter is detailed. Both third-order dielectric-and air-filled SIW band-pass filters are designed, fabricated and compared. They respectively achieve 0.56 +/- 0.24 and 0.18 +/- 0.17 insertion loss in the operating band of interest. The proposed filter is of particular interest for microwave and millimeter-wave low-noise receivers.