Coaxial versus rectangular waveguides for solid-state microwave circuits

It is shown that coaxial waveguides can have losses within a factor of 2.4 of rectangular waveguide. Furthermore, for impedance levels less than approximately 135 ohms, properly dimensioned coaxial guides are less lossy than rectangular guides of the same impedance level. The realization of this point is of significance in microwave solid-state circuit design.