It is a finite impulse response (FIR) digital filter, and its order is N/3(N is the sampling number in a period). The direct current in i P(i Q) can pass through this filter damplessly, while 3n harmonics damp thoroughly.

• 该滤波器具有线性相位的有限冲激响应 (FIR)数字滤波器 ,阶次为N/3(N为一个周期的采样点数 ) ,可使iP(iQ)的直流分量无衰减地通过 ,而 3n次谐波处的幅值衰减为0。