基于增益扩展现象的线性化技术在Doherty功放中的应用

在分析Doherty放大器特性基础上,研究了利用Doherty具有增益扩展特性的放大器线性化技术.深入分析了Doherty功放中辅助功放的栅压变化对增益扩展特性的影响,并讨论了据此将具有增益扩展特性的前级Doherty功放作为模拟射频预失真器与末级Doherty功放进行级联而构成的线性化功放.最后根据这一原理,采用一对MRF21010功放管所设计并优化的Doherty模拟预失真功率放大器与前级为平衡放大器、末级为相同Doherty功放的级联电路相对照,表明三阶互调可以改善15dB,效率提高2%.研究结果对高效率、高线性功放的设计具有实际意义.

Linearization Technology Based on Gain Expansion Phenomenon in a Doherty Amplifier

This paper discusses linearization technology of Doherty amplifier using gain expansion characteristic. We analyze the effection on gain expansion characteristic for the variation of the gate-biasing of the peaking amplifier. A RF analog predistorter is proposed using this driving stage Doherty amplifier with gain expansion phenomenon, then connect it to the final stage of the Doherty amplifier to buildup linearized power amplifier. This paper designes and optimizes the predistorter using two MRF21010. In order to verify the validity of the circuit, a Doherty amplifier using a balanced amplifier as its driving stage amplifier is presented. In comparison with Doherty PA using predistorter, 15dB improvement of IMD3 and 2% improvement of power-added-efficiency is achieved. The result is worthy to the design of high efficiency and high linearity microwave power amplifiers.