下面几个都叫啥滤波器哇？
1、
//! \brief     Runs a second-order filter of the form
//!            y[n] = b0*x[n] + b1*x[n-1] + b2*x[n-2] - a1*y[n-1] - a2*y[n-2]

static  _iq FILTER_SO_run(FILTER_SO_Handle handle,const _iq inputValue)
{
  FILTER_SO_Obj *obj = (FILTER_SO_Obj *)handle;

  _iq a1 = obj->a1;
  _iq a2 = obj->a2;
  _iq b0 = obj->b0;
  _iq b1 = obj->b1;
  _iq b2 = obj->b2;
  _iq x1 = obj->x1;
  _iq x2 = obj->x2;
  _iq y1 = obj->y1;
  _iq y2 = obj->y2;

  // compute the output
  _iq y0 = _IQmpy(b0,inputValue) + _IQmpy(b1,x1) + _IQmpy(b2,x2)
    - _IQmpy(a1,y1) - _IQmpy(a2,y2);

  // store values for next time
  obj->x1 = inputValue;
  obj->x2 = x1;
  obj->y1 = y0;
  obj->y2 = y1;

  return(y0);
}

2、
//! \brief     Runs a simplified second-order filter of the form
//!            y[n] = b0*x[n] - a1*y[n-1] - a2*y[n-2]

static _iq FILTER_SO_run_form_0(FILTER_SO_Handle handle,const _iq inputValue)
{
  FILTER_SO_Obj *obj = (FILTER_SO_Obj *)handle;

  _iq a1 = obj->a1;
  _iq a2 = obj->a2;
  _iq b0 = obj->b0;
  _iq y1 = obj->y1;
  _iq y2 = obj->y2;

  // compute the output
  _iq y0 = _IQmpy(b0,inputValue) - _IQmpy(a1,y1) - _IQmpy(a2,y2);

  // store values for next time
  obj->y1 = y0;
  obj->y2 = y1;

  return(y0);
}

3、
//! \brief     Runs a second-order filter of the form
//!            y[n] = b0*x[n] + b1*x[n-1] - a1*y[n-1] - a2*y[n-2]

static  _iq FILTER_SO_run_form_1(FILTER_SO_Handle handle,const _iq inputValue)
{
  FILTER_SO_Obj *obj = (FILTER_SO_Obj *)handle;

  _iq a1 = obj->a1;
  _iq a2 = obj->a2;
  _iq b0 = obj->b0;
  _iq b1 = obj->b1;
  _iq x1 = obj->x1;
  _iq y1 = obj->y1;
  _iq y2 = obj->y2;

  // compute the output
  _iq y0 = _IQmpy(b0,inputValue) + _IQmpy(b1,x1)
    - _IQmpy(a1,y1) - _IQmpy(a2,y2);

  // store values for next time
  obj->x1 = inputValue;
  obj->y1 = y0;
  obj->y2 = y1;

  return(y0);
}