基于GaN工艺的3.3~3.6 GHz Doherty功率放大器MMIC设计

A 3.3-3.6 GHz Doherty Power Amplifier MMIC Based on GaN Process

基于GaN工艺设计了一款饱和输出功率为44 dBm、功率回退为9 dB的非对称Doherty功率放大器。为了提高增益,在Doherty功率放大器前方增加驱动级。通过对主放大器的输出匹配电路进行阻抗匹配优化设计,去掉λ/4阻抗变换线;辅助功放输出阻抗采用RC网络等效代替,控制输出匹配电路相位为0°,确保关断时为高阻状态;合路点的最佳阻抗直接选取50Ω,从而去掉λ/4阻抗变换线。芯片仿真结果表明,在3.3~3.6 GHz时,Doherty功率放大器的饱和输出功率达到44 dBm以上,功率增益达到25 dB以上,功率附加效率(PAE)达到50%以上;功率回退为9 dB时,PAE达到34.7%以上。Doherty功率放大器的版图尺寸为3.4 mm*3.3 mm,驱动级功率放大器的版图尺寸为1.5 mm*1.7 mm。

An asymmetric Doherty power amplifier(DPA)with a saturated output power of 44 dBm and an output back-off of 9 dB was designed in a GaN process,with a front driving power amplifier(PA)added for gain increase.Afterwards,by optimizing the impedance matching network of main PA,theλ/4 impedance conversion line could be removed.The output impedance of auxiliary PA was replaced by RC network equivalently,and the phase of output matching was maintained at 0°,thereby ensuring high resistance state during turn-off.Also,the optimal impedance at closing point was directly selected as 50Ω,thus removing theλ/4 impedance conversion line.The simulation results show that when considering the frequency band of 3.3-3.6 GHz,a saturated output power,a power gain,and a power added-efficiency(PAE)of the proposed DPA are higher than 44 dBm,25 dB,and 50%,respectively.Besides,PAE can be above 34.7%at the output back-off of 9 dB.In addition,the chip size of DPA is 3.4 mm*3.3 mm,and that of driving PA is 1.5 mm*1.7 mm.