Directional couplers from 30 to 140GHz in silicon

In this paper directional couplers with reduced size, by lumped elements, inverted microstrip, and broadside coupled lines at 61, 110, and 122 GHz center frequency and up to 156-GHz bandwidth have been designed. The couplers show an isolation up to 40 dB. Different SiGe BiCMOS technologies with 250-nm and 130-nm feature width and 5 to 7 metal layers have been used. The measurement results have been compared to simulation results and good agreement has been observed.