Application of electro-thermal simulation and non-invasive in-situ waveform probing techniques to GSM PA optimization

The application of electro-thermal coupling simulation and high impedance dynamic loadline probing to the understanding and optimization of a GSM power amplifier (PA) is described. Electro-thermal simulation explains the temperature imbalance across the output HBT PA stage, which may lead to thermal collapse and amplifier damage. Direct probing of the voltage and current waveforms at different locations on the output combiner confirms the electro-thermal imbalance in the output PA HBT array. Results of the modified PA module are presented showing significant improvements in RF performance and ruggedness.