Structured fast Hartley transform algorithms

The flowgraph originally proposed for the computation of the radix-2 fast Hartley transform (FHT) is restructured for clarity and ease of implementation with hardware and software. By applying the transposition theorem to the newly formed flowgraph (which corresponds to a decimation-in-time algorithm), a decimation-in-frequency algorithm with a similar flowgraph is obtained. The number of operations for the two algorithms is the same because of an existing symmetry, which is also identical to that of another FHT algorithm recently proposed.