Analysis and Design of the SISL Waveguide Filter With Co-Designed Electric-Coupled SISL Resonators for Ku-Band Applications

This article presents a novel filter structure named by substrate-integrated suspended line (SISL) waveguide filter (SISLWF). Based on the SISL platform, by introducing the novel SISL via, both the magnetic-coupled air-filled waveguide resonators (AF-WRs) and the electric-coupled SISL resonators can be co-designed in the conventional SISL cavity. Magnetic-coupled TE101 mode of the AF-WR is excited by the SISL via and is utilized to design the passband. The co-designed electric-coupled SISL resonators, such as SISL open stub line (SISLOS) and a quarter of open-ended metal ring resonator (QRR), are utilized to generate transmission zeros (TZs) out of band. The SISLOS printed on G5 layer is designed as a notch filter and it is directly connected to the SISL via to generate multiple notch bands. At the end of the SISLOS, an electric-coupled QRR printed on G6 layer is also designed to generate a new TZ at higher band. Measured results show that for the proposed SISLWF, by optimizing the sizes of the SISLOS, QRR, and nonresonant SISL line, five TZs can be generated and controlled simultaneously.