This paper presents novel designs of Ka band transitions between standard rectangular waveguide and substrate integrated waveguide (SIW). The proposed transitions can provide simultaneous field and impedance matching. The transition with a height-tapered waveguide exhibits outstanding low-loss performance over an ultra-wideband range (entire Ka-band). And the other one with Chebyshev transformers has a compact profile and low loss better than 2dB in a bandwidth of 11GHz at Ka band. The simulation and analysis of the transitions are carried out with Ansoft HFSS.