Comparing SIW Resonator Types And Their Impact to RF Performance

SynMatrix will soon release support for substrate-integrated waveguide (SIW) filter structures using automatic 3D geometry workflows in Ansys HFSS. The research and development process to prepare this capability has been thorough - yet enlightening - as we complete the final touches on the interface.

Part of the R&D engineering process to develop a comprehensive library of tools and guidelines for SIW structures has yielded a comparison analysis of different types of SIW resonator shapes, some of which we would like to share publicly (Fig1).

There were two types we compared: A perimeter resonator design and the commonly-used open loop resonator (Fig2)

Each of these resonator types have different size and performance characteristics as summarized in the following table (Fig3):

This can be further elaborated when we evaluate the S-Parameter curve for each of these resonator types noting the unloaded Q and how this relates to the form factor of each resonator type (see Fig4):

Each scenario was evaluated at a central frequency of 30GHz with 10% BW, return loss of 20dB, and one transmission zero located at the higher side. Considering the wideband application with the I/O loading effect, the loaded Q will be 80% of the unloaded Q. The overall RF performance is shown above marked with center and band edge insertion loss values; under conservative considerations, 0.1-0.2 dB loss may also be added due to the I/O connection.

Readers can clearly see the impact of each of the different resonator types, particularly the impact to Q and insertion loss.