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K-band low-noise amplifier (LNA) chips are integrated in low-permittivity coplanar waveguide (CPW) and microstrip (MS) structures and are interconnected with substrate integrated waveguide (SIW) ports for direct applications in hybrid SIW technology. A commercial Hittite LNA chip is employed, and special transitions provide the interface between CPW or MS and SIW. The LNA with SIW-to-CPW transitions achieves more than 20 dB gain between 18 and 26.5 GHz, and input/output return losses remain below 10 dB between 21.5 and 26.5 GHz. Related design values for the LNA integration within SIW-to-MS transitions are: the gain is greater than 21 dB; the input/output return loss is better than 12 dB over the entire frequency range. Measurements of a back-to-back SIW-to-CPW transition are provided to put these values in perspective. The maximum noise figures are measured to be better than 4.6 and 4.2 dB, respectively, between 18 and 26.5 GHz. A comparison with measurements performed with an evaluation board supplied by the LNA manufacturer demonstrates successful K-band LNA chip integrations within CPW/MS and SIW.