宽带射频功放晶体管非线性输出电容研究

分析了GaN(氮化镓)HEMT(高电子迁移率晶体管)非线性输出电容Cout与宽带功放效率的关系。通过建立非线性电路模型分析得出,利用Cout控制漏极端电压电流波形能减轻对谐波阻抗的精确要求,使高效率阻抗区域扩大化,从而使宽带功放匹配变为可能。选用GaN HEMT器件设计2~3 GHz频段射频功率放大器,实测结果为该放大器最高漏极效率(DE)为81.7%,功率附加效率(PAE)78.3%,功率为40.75 dBm。在1 GHz带宽内PAE也可达65%以上。实测结果验证了原理分析的可靠性,提出的方法不仅可用于宽带GaN功率放大器设计,对其他类型的微波功放设计同样有借鉴作用。

Study of Nonlinear Output Capacitance of the Wide-band Power Amplifier

The relationship between nonlinear output capacitance Cout of GaN HEMT and the efficiency of the wide-band power amplifier is studied.Through the analysis of an established nonlinear circuit model,it is shown that the accuracy requirement on harmonic impedance can be reduced by using Cout controlling the waveform of the drain,which can enlarge the high efficiency zone.A highly efficient amplifier based on the principle is designed by using a Cree GaN HEMT device at 2~3 GHz band.It provides a drain efficiency of 81.7% and a power-added efficiency of 78.3% at a saturated power of 40.75 dBm.The method established in this paper can not only be used in wide-band microwave GaN PA,but it is also useful to other PA designs.