Understanding Substrate Integrated Waveguides (SIW)

This page explains the basics of SIW, which stands for Substrate Integrated Waveguide.

SIW is a modification of a dielectric-filled waveguide. It’s increasingly popular in RF (Radio Frequency) applications because of its many advantages.

As shown in Figure 1, an SIW structure consists of two metal ground planes – one on the top and one on the bottom – with a dielectric substrate sandwiched between them. A series of metallic vias (conductive holes) are placed between these two ground planes, forming the “walls” of the waveguide.

Due to its numerous benefits, as detailed below, SIW technology is increasingly used in 5G and other advanced wireless devices.

Dominant Mode in SIW

The presence of via holes along the sidewalls prevents the existence of the TM (Transverse Magnetic) mode. Therefore, the TE₁₀ (Transverse Electric) mode is used as the dominant mode in SIW.

In contrast, the SIW is derived from the dielectric-filled waveguide (DFW), which doesn’t have these via holes.

Benefits of SIW

Here’s a summary of the advantages offered by Substrate Integrated Waveguides:

• High Power Capability: SIWs can handle relatively high power levels.
• Low Radiation Losses: They exhibit minimal signal leakage and radiation.
• High-Density Integration: SIWs are suitable for compact and integrated circuit designs.
• Low Cost of Fabrication: Manufacturing SIWs is generally cost-effective.