A Quasi-elliptic SIW Filter in Quadruplet Scheme Based on a New Frequency-dependent Coupling Structure

Abstract

A fourth-order substrate integrated waveguide (SIW) bandpass filter (BPF) in quadruplet scheme based on a new frequency-dependent coupling (FDC) is proposed. The proposed FDC has a positive slope, and detail characteristics of the FDC structure are studied by the extracted impedance inverter. The FDC has advantages of flexibly adjusting slope and zero position. Based on the proposed FDC, a fourth-order SIW filter example with center frequency of 10 GHz and bandwidth of 300 MHz was designed. For the strong dispersive cross coupling path, three finite transmission zeros (FTZs) of the designed SIW filter can be achieved. For the demonstration, the designed filter was fabricated and measured. The responses of the measured and simulated results are matched very well, which has verified the feasibility of the new FDC structure.