Interpolated Filter 

A previous section explained that an IFIR filter is similar to a conventional FIR, but with the unit delay operator replaced by k-1 units of delay. k is referred to as the zero-packing factor. One way to realize this substitution is by the insertion of k-1 zeros between the coefficient values of a prototype filter. When specifying an IFIR architecture, the full set of prototype coefficients is supplied in the coefficient file, without the zeros implied by the zero-packing factor. The zero-packing factor is defined through the filter user interface. For example, consider the filter coefficient data in the .coe file shown in Figure 3-48.

前一節解釋了IFIR濾波器類似於傳統的FIR，但單位延遲運算元被k-1個延遲單位取代。 k被稱為零填充因子。 實現這種替換的一種方法是在原型濾波器的係數值之間插入k-1個零。 在指定IFIR架構時，係數檔案中會提供完整的原型係數集，零填充因子不會隱含零。 零填充因子通過過濾器使用者介面定義。 例如，考慮.coe檔案中的濾波器係數資料，如圖3-48所示。

If a zero-packing factor of k=2 is specified, the equivalent filter impulse response is shown in Figure 3-49.

如果指定零填充因子k = 2，則等效濾波器脈衝響應如圖3-49所示。

If the zero-packing factor is changed to k=3, the impulse response is as shown in Figure 3-50.

如果零填充因子變為k = 3，則脈衝響應如圖3-50所示。

These examples use a symmetrical prototype impulse response; this is not a restriction of the filter core. The prototype filter coefficient set can be symmetrical, non-symmetrical, or negative-symmetric.

這些例子使用對稱的原型脈衝響應; 這不是濾波器IP核的限制。 原型濾波器係數組可以是對稱的，非對稱的或負對稱的。