4电平S类数字功放的电平合成策略

Level synthesis strategy for 4-level class-S digital power amplifier

通过增加量化电平,Delta-Sigma调制器输出序列能够获得更好的调制性能。但在S类数字功放中,受限于开关功放的实现结构,多电平Delta-Sigma调制器输出脉冲序列无法直接驱动开关功放,需采用由多个开关功放单元构成的多电平开关功放。针对2比特Delta-Sigma调制器输出序列,分析了电平合成策略对4电平S类数字功放性能的影响,提出了两种优化的电平合成策略。理论分析和仿真结果表明,采用合适的电平合成策略,4电平S类数字功放可以获得更优的输出性能,尤其在输出功率回退状态下,电平合成策略对功放性能的影响更为显著。

The DSM(Delta-Sigma modulator)can get a better performance by increasing the quantizer′s levels.But the multi-bit DSM output cannot drive the SMPA(switch-mode power amplifiers)directly due to the multi-levels of DSM output in the class-S DPA(digital power amplifier).So the multi-level SMPA with multiple SMPA cells is needed.Several level synthesis strategies for 4-level class-S DPA based on 2 bit DSM were proposed and analyzed.The theory and simulation results show that,with an appropriate level synthesis scheme,the 4-level class-S DPA obtains a much better performance.Especially,the effect of level synthesis strategy is more remarkable in power back-off condition.