The butterfly arithmetic structures of three kinds of Cooley-Tukey radix-4 FFT algorithm and the simple calculation formulas for their common factors ( p ) of twiddle factor indexes are derived.

• 推导出三种Cooley -Tukey基 4FFT算法的蝶算结构及旋转因子指数公因子 p的简单计算公式 ；可显著减少求 p值的次数及单次 p值的运算量 .