A full Ka-band in-line suspended stripline (SSL) to rectangular waveguide transition is proposed in this paper. The antisymmetric probes are introduced to transform the quasi-TEM mode of the SSL to the TE10 mode of the rectangular waveguide. Two slots with polygonal shapes are cut on the two probes respectively to improve the bandwidth of the transition. To verify this design, a back-to-back structure is fabricated and tested. The experimental results show that the insertion loss of better than 0.32 dB and the return loss of more than 14.2 dB are obtained from 25 to 40 GHz. The measurement results agree well with the simulations.
