minimize the loss of signal energy into the substrate the transition functions by coupling the electric field in the waveguide 1 to the probe 12 of the transmission line extending into the waveguide the via holes significantly improve operation by preventing the propagation of energy into the substrate without the conductors 14 this energy would be lost e g by going off in spurious directions or by being reflected back into the rectangular waveguide it is noted that in fig1 the width of the substrate 8 extending into the waveguide 1 is less than the width of the waveguide 1 alternatively the portion of the substrate 8 inside the waveguide 1 may have a width equal to the full waveguide width it has empirically been found that ultimate performance is relatively insensitive to probe and substrate width it is possible to change the transition dimensions depending on the frequencies to be coupled and dielectric constant of the transition the shape of the probe specifically the angle 13 of the taper was found to have an effect on the bandwidth of the transition a large taper angle 13 yields an excellent return loss over a narrow frequency range while a smaller taper angle 13 increases the bandwidth but at the expense of return loss there may be additional transmission lines and circuit elements such as transistors diodes resistors inductors and capacitors connected to the coplanar transmission line these do not affect the operation of the transition provided they are not within one half wavelength of the waveguide the waveguide would usually extend in the direction of the viewer of fig1 and would be terminated with a short circuit at a.