Development of a New Electro-thermal Simulation Tool for RF circuits

10 1.2. The limitations of present simulation codes
Figure 1.12: Electro-thermal simulation with ADS from Agilent. Both self and mutual
interactions are included.
ity to activate the self-heating option (see e.g., the model MEXTRAM 504 for bipolar
junction transistors). Such models are equipped with a supplementary terminal, namely
a "thermal node", and include a default value for the thermal self-resistance. Hence,
the temperature increase above ambient is evaluated from the dissipated power and
considered, in turn, as a further input that modifies the thermally-sensitive parameters
(electro-thermal feedback). However, thermal interactions between active devices
integrated in the chip are not accounted for, which represents a considerable limitation
for the electro-thermal simulation of high-density ICs.
The possible solution to the problem could be the development of new schematic components,
so called Electro-thermal Feedback Blocks (ETFBs), as shown in Fig. 1.12.
Correctly constructed ETFB could take into account both types of electro-thermal
interactions that is for self and mutual ones.