Patent ID: 7246143

Claim:
A computer readable medium including a program having instructions, which when executed perform a radix 2 fast fourier transform on a digital series to produce signals in cyclically noncontinuous output bins that are useable in demultiplexing carrier signals, the instructions comprising: determining the number 2 s of FFT points, the output bin index O s , and the input signal array; determining the butterfly index for the last stage by Ψ S - 1 = O S ⁢ ⁢ % ⁢ ⁢ ( N 2 ) determining the butterfly index for each stage other than said last stage by Ψ l - 1 = Ψ l ⁢ ⁢ % ⁢ ⁢ ( N 2 S - l + 1 ) where % means modulo operation and where 1 varies from 1 to (S−1); using said butterfly index, calculating only those butterflies necessary for calculation of the output bins, providing to storage or further processing said signals in cyclically noncontinuous output bins, and applying said signals from said cyclically noncontinuous output bins to demultiplexing at least one carrier.