Design of an RF-power amplifier and optimization of the thermal properties

This bachelor thesis covers the realization and thermal properties optimization of a broadband radio frequency power amplifier in the Reader of Radio Frequency Identification applications in the Super High Frequency band from 5.725 to 5.875 GHz. Based on the preceding internship at the Fraunhofer Institute for Microelectronic Circuits and Systems, a number of different designs are developed in simulation to improve the thermal properties from some cost-effective aspects. Furthermore, some designs with the area of 4 cmx4 cm are selected for production and verification. Through measurement, their electrical characteristics and thermal properties are compared and evaluated respectively. Through the thermal simulation results and measurement results, it can be concluded that the AC ground and DC ground on the PCB of the RF-power amplifier have a great influence on the electrical characteristics and thermal properties. When AC ground and DC ground are separated from each other, the gain and impedance matching of transmission line is good. However, the heat on the PCB cannot be conducted well in the practical application, so the temperature of the chip might be too high, thereby degrading the electrical characteristics of the chip or even damaging the chip. On the contrary, the electrical characteristics of the PCB are slightly worse, while the thermal characteristics are greatly improved. Therefore, the design requirements need to be specifically considered in practice. In addition, increasing the density of the vias (reducing the via-to-via spacing) around the chip or reducing the thickness of the PCB can slightly improve the electrical characteristics and thermal properties of the PCB. Based on the consistency of the measurement results and the simulation results, it can be inferred that if the area is increased, the thermal performance will be significantly improved. Therefore, in the practical application, if the front end of the RFID reader has more space left for the RF-power amplifier, it can also be considered to separate the AC ground from the DC ground on the PCB with larger area, such as 5 cmx5 cm.


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