In this paper, substrate noise suppression for 0.18$\mu$m SiGe BiCMOS and fully-depleted silicon on insulator (FDSOI) processes is evaluated and compared. For both technologies, the most effective way for substrate noise reduction is assessed to identify the best approach for noise mitigation. The results show that the FDSOI process with large separation between analog and digital blocks is a more efficient substrate crosstalk suppression method compared to the best case in the SiGe BiCMOS process.