动态偏置射频功率放大器研究

Investigation of RF Power Amplifiers in Dynamic Bias Operation

摘要: 分析了功率放大器输入输出响应特性与栅极偏置电路时间常数的关系，以及信号通过功率放大器后的矢量幅度误差(EVM)和邻信道功率抑制比(ACPR)。并基于MW4IC2230设计了工作于2 GHz频段，输出33 dBm的TD-SCDMA三载波射频功率放大器，以验证该关系。当动态偏置电路时间常数为1 ms时，功率放大器输出EVM为2.5%，ACPR为?43 dB。根据TD-SCDMA物理信道特点，提出对偏置电路的控制可以比传输信号起始时刻提前，当该提前量为1.5 μs、动态偏置电路时间常数为1 ms时，功率放大器输出EVM为1.8%，ACPR为?45 dB，满足TD-SCDMA系统标准要求。

Abstract: Radio frequency power amplifiers are analyzed in respect of their characteristics including the relation between the output response, the time constant of the gate dc bias circuits, error vector magnitude (EVM), adjacent channel power ratio (ACPR) of the output signal. A power amplifier with 33 dBm output power at 2 GHz is desighed, tested to verify the analysis. When the dynamic gate bias voltage works in a time constant of 1 ms, the amplifier is measured with EVM of 2.5%, ACPR of ?43 dB. After a redesign for the control signal with 1.5 μs ahead shift, EVM of 1.8%, ACPR of ?45 dB are achieved, which are compatible with the standards of TD-SCDMA.