Low-cost Implementation of a Waveguide-based Microwave Filter in Substrate Integrated Waveguide (SIW) Technology

Abstract

This paper presents the design and practical implementation of a waveguide-based microwave filter in Substrate Integrated Waveguide (SIW) technology. The use of SIW technology for implementing waveguide filters makes the presented design specially aimed for being used in undergraduate courses related to microwave engineering and filter designing. Their low cost and easiness from the filter fabrication point of view allows their use in microwave laboratory courses where students can implement their own theoretical filter designs and measure their frequency response. The requiring mechanics in the manufacturing of microwave filters in waveguide technology (both rectangular and circular) makes its use practically unfeasible in academic laboratories because of its cost. For this reason, a practical design example of a waveguide iris filter using the impedance inverter model is proposed in this paper for academic laboratories, using SIW technology. This is a low cost and easy to manufacture technology. The overall process includes the design of the ideal band-pass prototype filter using the impedance inverter and its implementation in an inductive iris-coupled waveguide filter, by using a developed electromagnetic simulator based on the mode-matching technique. Finally, the equivalent filter in SIW technology is obtained and optimized by using HFSS simulator, including a SIW to microstrip transition. A prototype of the designed filter has been fabricated and measured, showing a good agreement between measurements and simulations.