Whether recognized or not, SPICE simulators are at the heart of many or most circuit simulators. So the material that is about to be described can be of use to you if you use numerous other circuit simulators in addition to SPICE. A critical requirement of any simulator that qualifies it for use at microwave frequencies is that the simulator absolutely must have the capability of modeling transmission lines with frequency-dependent loss. Frequency-dependent loss is so pervasive at microwave frequencies that any tool without this capability will be of little use.

Figure 7.1: A Plot of Frequency-Dependent Loss