https://www.dolphmw.com/products/waveguide-probe-coupler/ Waveguide Probe Coupler In waveguide coupling probes, a probe inside a coaxial line is used to distribute energy into a waveguide. As current starts flowing in the probe, an electric field is set up and it gets detached from the probe to the waveguide. The probe (also called a probe antenna) radiates energy equally into the waveguide where it is inserted. Probe antenna insertion is usually made perpendicular to the length of the waveguide, at a distance equal to the quarter wavelength from the shorted end of the waveguide. For more information. feel free to call us and discuss your needs with one of our sales engineers.