In the present work a custom-developed, avalanche noise diode model is used in a commercial CAD software and is applied to three real case scenarios. The considered diode is the 20um2 p-i-n diode developed with commercial 130-nm SiGe BiCMOS Infineon technolog, whose model is available in literature. Simulations are carried out with the diode connected to: an attenuator, a switch, and a SIW band-pass filter. The equivalent noise temperature at the output of all the above systems is evaluated, showing realistic responses. The originality of the study lies in the fact that no avalanche noise diode models are available in modern CAD, and results show that many circuits can be rigorously studied with the proposed approach.