A dual-mode quasi-elliptic filter in air-filled substrate integrated waveguide technology

This paper presents a novel quasi-elliptic band-pass filter in air-filled substrate integrated waveguide (SIW) technology. It is based on a dual-mode cavity resonator and features a frequency response with two poles and two transmission zeros. This structure exploits the properties of the air-filled SIW, which has been recently proposed to realize integrated interconnects and allows for reduced losses. The geometry of the air-filled area in the SIW resonator allows controlling the pass band of the filter, by setting the frequency of the first and second cavity modes. The position of the input/output microstrip lines, conversely, permits to modify the location of the transmission zeros. As an example, a band-pass filter operating at the frequency of 3.6 GHz, with a relative bandwidth of 1.4% and two transmission zeros, has been designed, fabricated, and experimentally verified.