Compact and Low-Loss U-Band Shielded Asymmetrical Coplanar Stripline to Rectangular Waveguide Transition

A compact and low-loss U-band transition from the rectangular waveguide to the shielded asymmetrical coplanar stripline (SACPS) is presented. A shielding cavity and the asymmetrical coplanar stripline (ACPS) transmission line are combined to construct the SACPS transmission line. Similar to the ACPS transmission line, the SACPS has the quasi-TEM dominant mode and do not need via holes and can be capable of shunt as well as series surface mounting of devices. In addition, owing to the removed radiation losses and low dielectric losses, the SACPS transmission line has low losses which is beneficial for applications at millimeter wave. The strip plate of the SACPS can be extended into the electrical wall of the rectangular waveguide as an E-plane probe and excite the TE10 mode at where the electrical field is the strongest in the rectangular waveguide. At the frequency range of 40–60 GHz, the measured and simulated return losses are larger than 10 and 20 dB, respectively, while the measured and simulated insertion losses are less than 0.7 and 0.2 dB, respectively.