Patent ID: 7693034

Claim:
A circuit for converting frequency domain information to time domain information comprising: a. an Inverse Fast Fourier Transform circuit having a length of N samples, the Inverse Fast Fourier Transform circuit adapted to receive input data of length N samples, to circularly shift the input data by m samples; and to generate output data of length N samples not multiplied by external rotator coefficients that are circularly shifted by m samples, where m is less than N; and b. a Cyclical Prefix Insertion circuit adapted to insert a cyclical prefix of length m, the Cyclical Prefix Insertion circuit having; 1. a first switch, connected to the Inverse Fast Fourier Transform circuit; 2. a buffer, having an input connected to the first switch and an output, the buffer having a length m; and 3. a second switch, coupled to the first switch and to the buffer, wherein the first and second switches selectively couple the output of the buffer and the Inverse Fast Fourier Transform circuit to an output of the second switch; wherein the N samples is a power of 2 and wherein the Inverse Fast Fourier Transform circuit implements an algorithm selected from the group consisting of Radix-2 and Radix-2 2 algorithms; and wherein the Inverse Fast Fourier Transform circuit further comprises a plurality of butterfly circuits, rotator circuits and multiplier circuits with memories, all coupled to a control circuit, and the Inverse Fast Fourier Transform is adapted to circularly shift the input data by m samples by modifying memory contents for at least one multiplier circuit with memory and modifying the control for at least one rotator circuit.