Howtosignalprocessing
- Why is bit reversal needed for FFT?
- What is bit reversal in FFT?
- How is bit reverse addressing used in FFT computations?
- Why is FFT efficient?
Why is bit reversal needed for FFT?
FFT and IFFT Blocks Data Order
The FFT block enables you to output the frequency indices in linear or bit-reversed order. Because linear ordering of the frequency indices requires a bit-reversal operation, the FFT block may run more quickly when the output frequencies are in bit-reversed order.
What is bit reversal in FFT?
Bit reversal is most important for radix-2 Cooley–Tukey FFT algorithms, where the recursive stages of the algorithm, operating in-place, imply a bit reversal of the inputs or outputs. Similarly, mixed-radix digit reversals arise in mixed-radix Cooley–Tukey FFTs.
How is bit reverse addressing used in FFT computations?
Bit-reversed addressing is a special feature provided in the dsPIC® architecture to support efficient implementation of FFT algorithms. Given the address of a particular element in the array, the dsPIC hardware automatically computes the address of the next element in the bit-reversed sequence.
Why is FFT efficient?
In an FFT, D and E come entirely from the twiddle factors, so they can be precomputed and stored in a look-up table. This reduces the cost of the complex twiddle-factor multiply to 3 real multiplies and 3 real adds, or one less and one more, respectively, than the conventional 4/2 computation.
