We fabricated and characterized heterojunction field effect transistor radio frequency (RF) power amplifier (PA) test fixtures, for wireless applications, with various printed circuit board (PCB) structures. The RF matching and bias circuits of the test fixtures were designed so that they had the same RF characteristics. The only source of the variation of the RF gain (S21) was different thermal characteristics of each PCB. The values of the junction temperature (TJ) and the junction-to-ambient thermal resistance (RJA) of each test fixture were shown to be changed as much as 80°C and 30°C/W, respectively, by the change of PCB structures. The change of RJA was shown to be originated from the change of the PCB thermal resistance, assuring that the structure of the PCB was the dominant factor in determining RJA . Finally, we obtained a universal relation between S21 of the amplifier and TJ. This work suggests that thermal budget of PCB is as important as that of package in wireless RF equipments.
- Power amplifier (PA)
- Printed circuit board (PCB) thermal resistance
- Radio frequency (RF)
- Thermal design
ASJC Scopus subject areas
- Electrical and Electronic Engineering