Microstrip to waveguide transition
Image of the Microstrip to waveguide transition.

The transition between a microstrip line and a rectangular waveguide is accomplished by inserting a probe, connected to the microstrip line on the same substrate, into a slot in the broad wall of a rectangular waveguide. These transitions are useful for the device and circuit characterization of millimeter-wave MICs and MMICs. Some systems may also require transitions between microstrip and waveguide to combine IC’s and waveguide components.

Operation of the transition is similar to that of a coaxial to waveguide transition where the extension of the probe couples strongly to the TE10 waveguide mode by acting as a short capacitive monopole.

Typical reflection coefficients versus frequency
Typical transmission coefficient versus frequency