Miniaturizing SIW Filters with slow wave Technique

Filters are an inevitable part of any communication system. State-of-the-art devices are designed with miniaturization as an important criterion. Though miniaturization gained considerable attention, application of slow wave technique as a miniaturizing technique wasn't explored much. Furthermore, the analysis of slow wave filters in terms of its characteristic parameters like slow wave factor (SWF) and group delay has not yet been attempted. This work performs a comparative study of miniaturized inductive post and iris substrate integrated waveguide SIW band-pass filters. Inductive post and iris filters are designed, fabricated and analyzed. Implementation of slow wave requires a double layer topology, which results in physically separating the electric and magnetic fields. This helps in miniaturization. Application of slow wave technique improved the insertion loss by 0.23% for the inductive post filter and 7.53% for iris filter. SWF and group delay were found to be better in the iris filter. The inductive post filter was 38.17% and 61.36% miniaturized in size and area, respectively and iris filter, 56.35% and 72.72%, respectively. The miniaturized iris filter was fabricated and the results were validated by measurements. The quality factor for miniaturized iris and inductive post filters were found to be 918.45 and 755.15 respectively.