https://www.dolphmw.com/products/double-ridged-waveguide-tube/ Rectangular Waveguide Definition Dolph Microwave Double-ridge waveguide tubes are rectangular waveguide tube with two ridges protruding parallel to the short wall. Double-ridge waveguide tube are widely used in antenna and microwave systems since they exhibit low cut-off frequency, broad frequency band, low characteristic impedance, and capability of matching to coaxial cable.All Rights Reserved