HBT射频功率放大器热优化的研究

Radio frequency (RF) power amplifier (PA) is a key component for a wireless transmitter. It has been widely used in the field of mobile communication, bluetooth, wireless local area networks (WLAN) and other modern communication systems. Maturity of thermal management is the premise for its further development. The purpose of this project is to explore the thermal optimization technology for HBT RF PA design. According to the disadvantages in current thermal processing, such as high cost, complex technology, poor heat dissipation and lack of theoretical direction, we focus on the affecting factors for temperature rise and its non-uniform distribution. In order to improve the ability of heat dissipation and achieve a low steady-state temperature, a shortest collector metal cooling path connected with the heat source is added when the research on temperature gradient in device is completed. The thickness, geometry and position of the metal are optimized at the same time. After the analysis on isothermal of multi-finger structure, we propose the computing method for thermal resistance matrix network with respect to heat flux down to substrate and up to metal. Temperature field model is then developed for guiding the design of thermal compensation to obtain a uniform temperature distribution. As a result, an optimization theory is developed for RF PA thermal design.

射频功率放大器是无线发射机中的关键组成部分，广泛应用于移动通信、蓝牙、无线局域网等现代通信领域中。热处理技术的成熟是推动射频功放进一步发展的前提。本项目的研究目的在于探索HBT射频功率放大器设计中的热优化技术。针对目前热优化处理中存在的不足，如成本高，工艺复杂，散热能力差，均匀度热设计缺乏理论指导等问题，对温升及其非均匀分布的影响因素展开研究。通过对器件内部温度梯度的研究，拟增加集电极金属散热路径以最短路径连接热源集中区，并对金属厚度、形状、位置进行优化，以改善散热能力，降低稳态温度；通过对多指等温线的分析研究，同时考虑热源向下至衬底以及向上至金属的热流分布，拟分区讨论并提出热阻矩阵网络精确的计算方法，构建温度场模型；通过温度计算分布指导热补偿设计，改善功率单元的非均匀温度分布，为射频功放的热设计提供理论指导。

热处理技术的成熟是推动射频功放进一步发展的前提，本项目的研究目的在于探索HBT射频功率放大器设计中的热优化技术。因此，针对目前热优化处理中的不足，我们对升温以及非均匀分布的影响因素等进行了研究。通过对HBT器件内部热源以及热生成机制的研究，提出了器件次集电区优化掺杂的热结构设计；通过对功率单元散热路径的研究，提出了提高散热效率的功率单元结构；通过采用Volterra级数展开射极镇流电阻对非线性影响的定量计算模型的研究，为非均匀镇流电阻改善热提供理论支持。