改进负载调制的GaN Doherty功率放大器及其线性化

Load Modulation Improvement and Linearization of GaN Doherty Power Amplifier

摘要: 在分析传统Doherty负载调制的基础上，通过选取合适的峰值放大器负载阻抗和采用较高的偏置电压，增强了Doherty功率放大器的负载调制，使其适用于大范围（9dB）回退情况下的应用。为了验证分析的有效性，设计和实现了一个具有100MHz瞬时带宽的2.55GHz GaN Doherty功率放大器。测试结果表明：在工作带宽内饱和功率约为49.4dBm，平均峰值效率为64%，9dB回退时的平均效率约为40%。当使用5载波100MHz带宽LTE-advanced信号激励时，在平均输出功率为40.2dBm时效率可达40.3%，经过数字预失真校正过的邻道泄漏比（ACLR）低于-48dBc，达到较好的线性度。

Abstract: To improve load modulation and enhance efficiency over 9 dB backoff range, the peaking amplifier is designed to achieve enough output current by choosing optimal load impedances and higher biasing voltage. A GaN Doherty power amplifier (PA) with 100 MHz instantaneous bandwidth at 2.55 GHz was designed and measured. The realized Doherty PA shows 9 dB backoff efficiency of about 40% and average peak efficiency of 64% at saturation power about 49.4 dBm. When driven with 100 MHz LTE-advanced signal, the PA achieves adjacent channel leakage ratio of -48 dBc after digital predistortion at an average output power of about 40.2 dBm with efficiency of 40.3%.