TMS320F280039C: 关于PMP23338项目中陷波滤波器Notch的预矫正问题

Part Number: TMS320F280039C
Other Parts Discussed in Thread: PMP23338

TI专家您好！

在PMP23338中关于预校正陷波滤波器的有如下疑问：

为什么在函数 SPLL_1PH_NOTCH_coeff_calc中的预校正双线性变换方法和正常的方法不同？就是wn2的求法不理解，按照正常的方法应该是如下所示，麻烦专家们解答下，谢谢了！

static inline void SPLL_1PH_NOTCH_coeff_calc(SPLL_1PH_NOTCH *spll_obj,
                                             float32_t c1, float32_t c2)
{
    float32_t notch_freq;
    float32_t temp1,temp2;
    float32_t wn2;
    float32_t Ts, Fs;

    notch_freq=2*3.14159265f*spll_obj->fn;
    Ts = spll_obj->delta_t;
    Fs=1/Ts;

    //
    // pre warp the notch frequency
    //
    wn2=2*Fs*tanf(notch_freq* ((float32_t)3.141592653589)*Ts);

    temp1= 4*Fs*Fs + 4* wn2 * c2 * Fs + wn2*wn2;
    temp2= 1/ ( 4*Fs*Fs + 4* wn2 * c1 * Fs + wn2*wn2);

    spll_obj->notch_coeff.b0 = temp1* temp2;
    spll_obj->notch_coeff.b1 = (-8*Fs*Fs + 2* wn2* wn2)* temp2;
    spll_obj->notch_coeff.b2 = (4*Fs*Fs-4*wn2*c2*Fs+wn2*wn2)*temp2;
    spll_obj->notch_coeff.a1 = (-8*Fs*Fs + 2* wn2* wn2)*temp2;
    spll_obj->notch_coeff.a2 = (4*Fs*Fs-4*wn2*c1*Fs+wn2*wn2)*temp2;
}