Octave Bandwidth High-Performance Microstrip-to-Double-Ridge-Waveguide Transition

This letter presents a microstrip-to-double-ridge-waveguide transition with high performance in the octave bandwidth operation between 6 and 12 GHz. The structure is based on a three-chamfered-step transformer supported directly over the microstrip line without soldering. The electric contact is ensured by the pressure between the first step of the transformer and a groove in the microstrip line. The transition is formed by two halves, minimizing the manufacturing complexity and the loss contact. A sequential procedure has been followed in the design process. Initially, a port directly feeding the planar structure has been considered, obtaining a simulated return loss level better than 25 dB in the whole operation band. Afterward, feeding through an SubMiniature version A (SMA) coaxial connector, a simulated return loss level better than 20 dB has been obtained. In order to verify the above theoretical simulations, a back-to-back arrangement has been measured, connecting two similar transitions. The prototype shows an insertion loss for a single transition lower than 0.8 dB in the 67% fractional bandwidth from 6 to 12 GHz.