Folded ESIW Bandpass Filter With Inverters Based on Short-Circuits Along the Folding Gap

Abstract

The benefits of empty substrate integrated waveguide (ESIW) are already well-known and contrasted in the literature, as well as the benefits of designing filters and other devices according to this technology. Recently, the Folded-ESIW (FESIW) has been presented, that halves the width of the original ESIW waveguide and maintains the cross-section area with good performance indexes and a similar bandwidth. This paper discusses three alternatives to design bandpass filters based on FESIW using irises, vertical cylindrical soldered posts or short-circuits along the folding gap. The most robust and effective way of manufacturing them is objectively determined. A prototype example is, for the first time, completely designed, manufactured and measured, with results of 3.71% fractional bandwidth at the central frequency of 14 GHz, 1.39 dB of filter insertion loss and Q-factor around 1300; this proves the feasibility and reliability of this new type of filters in comparison with other filters based on similar topologies.

Keywords

• Folded
• empty substrate integrated waveguide
• filter
• post
• iris
• short-circuit