FFT IP Core: User Guide

ID 683374
Date 11/06/2017
Public
Document Table of Contents

1.3.2. Variable Streaming FFT

The variable streaming FFT implements two different types of FFT. The variable streaming FFTs implement either a radix-22 single delay feedback FFT, using a fixed-point representation, or a mixed radix-4/2 FFT, using a single precision floating point representation. After you select your FFT type, you can configure your FFT variation during runtime to perform the FFT algorithm for transform lengths of 2m where 3 ≤ m ≤18.

The fixed-point representation grows the data widths naturally from input through to output thereby maintaining a high SNR at the output. The single precision floating-point representation allows a large dynamic range of values to be represented while maintaining a high SNR at the output.

The order of the input data vector of size N can be natural or digit-reversed, or -N/2 to N/2 (DC-centered). The fixed-point representation supports a natural or DC-centered order and the floating point representation supports a natural, digit-reversed order. The FFT outputs the transform-domain complex vector in natural or digit-reversed order. You can specify the transform direction on a per-block basis using an input port.