Monolithic integration of microstrip line couplers for automotive radar applications at 77 GHz using a Si-HBT technology

A branch-line, rat-race and a reduced-size branch-line coupler have been realized in a modern SiGe:C bipolar technology for application in automotive radar systems at 77 GHz. The paper describes the design methodology of passive circuits on lossy Si-based substrate up to 110 GHz and gives measurement results of the manufactured circuits.