This paper presents a Rotman lens design in the K-band, using Substrate Integrated Waveguide (SIW) technology with microstrip transitions. A five beam prototype feeding a 7-element array working at K-band has been fabricated and tested. The design was verified using the electromagnetic simulation software CST Microwave Studio, and a working prototype was manufactured by standard PCB fabrication. For this design, a metal fill in the gaps was used to replace the tracks to test a new technique for filling the tracks with brass, which allowed cost savings and decreased implementation time. The experimental results demonstrate that the design was adequate; the isolation between input ports and between output ports is below 15 dB in the range of 18.5 to 22 GHz. Furthermore, the measured results show a behavior similar to the simulations.