A novel broadband transition of Rectangular waveguide-to-Coplanar Waveguide without dielectric substrate

A novel broadband transition of Rectangular waveguide-to-Coplanar Waveguide without dielectric substrate is proposed in this paper. The transition without dielectric substrate means a low dielectric loss can be used at higher frequency compared with traditional CPW. The transition is designed based on a thin medal ridge which is approximately a square of cosine. On the other hand, the strip of CPW which has the same height with the medal ridge is connected to the ground. Thus, the transition not only is fabricated easily but also acts as a heat sink for circuit with active device. The simulation result is achieved by FDTD method, and from the result we can see that the return loss and insertion loss operating at 70GHz to 120GHz are better than 15dB and 0.3dB, respectively. The transition finds numerous applications in millimeter wave systems, such as mixers and multipliers and so on. To facilitate the design at arbitrary frequency range, the key parameters of the transition are analysis and some rules are concluded.