基于RF-PWM的主动谐波消除方法

An active harmonic elimination method based on multi-level RF-PWM for constant envelope signal

摘要:

开关模式功放(SMPA)适合于恒包络信号的高效功率放大，但会产生大量高次谐波，不仅对开关功率器件是一大挑战，还可能引入额外失真，对滤波器提出更高要求。针对上述谐波问题，根据叠加原理，在射频脉冲宽度调制(RF-PWM)的基础上，提出了一种针对恒包络信号的主动谐波消除方法。该方法通过选取多个特定的比较门限，对构成多电平输出脉冲的多个子脉冲的脉冲宽度进行控制，使其特定次谐波分量相互抵消，从而实现对特定次谐波的主动消除。该方法一方面可显著降低恒包络信号高效放大对滤波器的设计要求和实现难度，适合宽频段应用；另一方面可提高编码效率，有利于提高SMPA对恒包络信号的功放性能。仿真结果验证了该方法的可行性和有效性。

Abstract:

Switch Mode Power Amplifier(SMPA) is suitable to the efficiency amplification of constant envelope signal，but numerous higher harmonics will be generated. This is not only challenging for the switching power devices which may introduce distortion due to bandwidth limitations，but also put forward a higher requirement on the filter. According to the principle of superposition，an active harmonic elimination method for constant envelope signal is presented based on Radio Frequency Pulse Width Modulation(RF-PWM). This method adopts multiple selective thresholds and controls the pulse widths of the sub-pulses, which constitutes the multi-level output pulses. Then, the selective harmonics of RF-PWM can be actively eliminated by canceling the corresponding harmonics of multi sub-pulses. Consequently, the proposed method can significantly decrease the design requirements and implementation difficulty for the filter, which is good for wide band use. Furthermore, the coding efficiency is increased, which provides benefit to improve the amplification performance of SMPA for constant envelope signal. Finally, the feasibility and validity of the proposed method is verified through the simulations.