# Post-wall waveguide

A post-wall waveguide (also known as substrate integrated waveguide (SIW) or a laminated waveguide) is a synthetic rectangular electromagnetic waveguide formed in a dielectric substrate by densely arraying metallized posts or via-holes which connect the upper and lower metal plates of the substrate. The waveguide can be easily fabricated with low-cost and mass-production using through-hole techniques where the post walls consists of via fences. The post-wall waveguide is known to have similar guided wave and mode characteristics to the conventional rectangular waveguide with equivalent guided wavelength.

For instance, the equivalent width of a rectangular waveguide compared to a SIW is described in the approximation:

${\displaystyle a_{RWG}=a_{SIW}-1.08(2r)^{2}/p+0.1(2r)^{2}/a_{SIW}}$

where ${\displaystyle p}$ is the distance between the posts in the post wall, ${\displaystyle r}$ describes the radius, and ${\displaystyle a_{RWG}}$ as well as ${\displaystyle a_{SIW}}$ are the widths of the rectangular waveguide and SIW respectively.