Two right-angle microstrip to waveguide transitions suitable for metal backed substrates

For some applications the use of metal backed substrates is advantageous. The solid backside-metallization provides a good heatsink and gives the possibility to produce MMIC-cavities by milling. However, the circuit design is bounded to one layer, and therefore the choice of suitable waveguide transitions is limited. Especially if right-angle transitions are needed, no structures are known to the authors that can be produced easily by single-layer etching and milling processes. In this contribution two microstrip line (MSL) to rectangular waveguide transitions are presented that can be used with metal backed substrates. One of the transitions can be fabricated even without via holes. Designs are presented for the E-band and the Ka-band, but the principles can be scaled to other frequency ranges.