调整峰值功放电流响应提高效率的LTE-A Doherty功放

Aligned Current Response in Peaking Way of Doherty Amplifier to Improve the Efficiency Consistency for LTE-Advanced Application

介绍了一种利用宽带输入匹配网络调整峰值功放输出电流,改善Doherty功放负载调制效果和带内效率的设计方法。理论分析表明,Doherty功放中峰值功放C类偏置情况下带来的带内不一致开启特性会影响输出电流和负载调制效果。通过引入宽带输入匹配网络,能有效改善它的开启不一致性。为验证分析结果设计了具有宽带(采用简易实频技术)和窄带两种不同输入匹配网络,用于2.15GHz频段LTE-A的Doherty功放。仿真和测试结果表明,功放的输出功率超过49d Bm,在7d B回退功率处,宽带输入匹配Doherty功放的带内效率达到42%以上,效率波动由10%降低到2%。使用100MHz宽带LTE-A信号经过线性化改善后,在40d Bm输出时,宽带输入匹配网络的Doherty功放上下边带ACLR(adjacent channel leakage ratio)指标为-45.1/-44.9d Bc,效率为40.5%,均优于窄带输入匹配网络的Doherty功放。

This paper proposed a design method to improve the load-modulation mechanism and efficiency of Doherty by adopting the broadband input matching circuit to align the output current of peaking power amplifier( PA). From analytical investigation,the current response of the peaking PA in Doherty gives an inconsistent turn-on behavior due to the deep class C bias condition. To remove this inconsistent turn-on behavior,simplified real frequency technique( SRFT) is proposed. To verify this proposed method,two Doherty PAs with different input match are designed to work at 2. 15 GHz for comparison. These simulated and measured results show that the output of PAs is higher than 49 d Bm. At 7d B back-off power region,PA with broadband input matching gives a lowest efficiency of 42% and an improved efficiency deviation from 10% to2% in working band. Excited by 100 MHz LTE-A signals,with digital pre-distortion( DPD) PA presents an higher and lower band ACLR of- 45. 1 /- 44. 9d Bc around output power of 40 d Bm and efficiency of 40. 5%,which is both better than narrow band design.