高效率包络跟踪功率放大器

High Efficiency Envelope Tracking Power Amplifier

基于功率放大器(PA)效率提高技术,设计了一套包络跟踪(ET)功率放大器系统,射频(RF)功率放大器的漏极采用三电位G类结构的包络跟踪放大器提供自适应电压偏置,包络放大器包含两个自主设计的横向双扩散晶体管(LDMOS)开关管,RF功率放大器采用自主研发的LDMOS功率放大管进行优化匹配设计。在连续波(CW)信号激励下,28 V恒定电压下测得功率放大器在2.11 GHz下饱和输出功率为40 d Bm,饱和漏极效率为51%,输出功率回退8 d B时的漏极效率为22%,采用包络跟踪后提高至40%。在8 d B峰均比(PAR)WCDMA信号激励下,28 V恒定电压下测得功率放大器的平均效率为21%,采用包络跟踪后提高至35%。实验结果表明,采用自主设计的LDMOS开关管和LDMOS功率放大管应用到包络跟踪系统后,功率放大器的效率明显提高,验证了包络跟踪技术的优势和自主设计的LDMOS管芯的优越性。

Based on the efficiency improvement technology of power amplifier（ PA）,a PA system using envelope tracking（ ET） was designed. The drain of the radio frequency（ RF） PA used a threelevel class-G modulator with two self-designed laterally double diffused metal oxide semiconductor（ LDMOS） switching transistors provided for the adapted drain bias. The matching design of the RF PA was optimized based on the self-designed LDMOS transistor. Under excitation of continuous wave（ CW）signal,the RF PA achieves a maximum output power of 40 d Bm and a maximum drain efficiency of 51%at the 2. 11 GHz,and the drain efficiency at 8 d B back off output power can be increased from 22% to40% at the constant supply of 28 V with envelope tracking. When excited by 8 d B peak-to-average ratio（ PAR） WCDMA signal,the overall average efficiency of the PA can be increased from 21% to 35% at constant supply of 28 V with envelope tracking. The test results show that the efficiency of the PA is improved a lot with the self-designed LDMOS switching transistors and self-designed LDMOS power transistor applied in ET system,which verifies the advantage of ET and self-designed LDMOS chip.