Microstrip to surface mounted foam-based waveguide transition for Ka-band filter integration

This paper introduces a novel transition structure between a microstrip line and a surface mounted waveguide. The waveguide structure is based on foam material and comprises a flange cavity, the design of which aims both to achieve the impedance matching of the transition and to enable potentially a fully automated assembly onto an RF printed circuit board (PCB), complying so with surface mounted device (SMD) technology. The new concept has been applied to two 30GHz waveguide filter designs, presenting respectively a Chebyshev and a pseudo-elliptic response.