Wideband and low‐loss transition from low‐temperature co‐fired ceramic laminated waveguide to subminiature coaxial connector for millimetre‐wave applications

Abstract

This letter presents a novel transition scheme from laminated waveguide (LWG) to subminiature coaxial connector with wideband and low-loss performance. The laminated waveguide is achieved using multilayer low-temperature co-fired ceramic (LTCC) technology. In the conventional transition scheme, a length of grounded coplanar waveguide (GCPW) is used to connect the LWG and coaxial connector to obtain a wide bandwidth, which increase the transition size and radiation loss, especially in millimetre-wave (MMW) band. To realize a compact and low-loss LWG-to-coaxial connector transition, the GCPW line is removed and the whole LTCC transition structure is designed underneath the coaxial connector. Moreover, two stages of waveguide step are introduced to constrain the electromagnetic field in the transition for lower radiation loss, which also contributes to the wideband impedance matching. The back-to-back transition is designed and fabricated with LTCC technology to validate the proposed transition scheme. A measured bandwidth of 44% from 27.3 to 42.9 GHz is achieved under |S11| < −15 dB and the insertion loss of single transition is about 0.4 dB.