Summary: FFT structures with different memory layout and interconnection patterns are occasionally useful for certain applications. These alternate structures include decimation-in-frequency FFTs with in-order outputs, decimation-in-time FFTs with in-order inputs, structures with both in-order inputs and outputs, and constant-geometry structures with the same connection pattern in every stage.
![]() Figure 1: Decimation-in-frequency radix-2 FFT with bit-reversed
input.
This is an in-place algorithm
in which the same memory can be reused throughout the computation. |
![]() Figure 2: Decimation-in-frequency radix-2 FFT with in-order input and output. It can be computed in-place
if two butterflies are computed simultaneously. |
![]() Figure 3: This constant-geometry structure has the same interconnect
pattern from stage to stage.
This structure is sometimes useful for special hardware. |