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US 2003/0169823 A1Published application
Efficient FFT implementation for ADSL
AssigneeTioga Technologies Inc.
InventorGuy Reina
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Abstract
A method and apparatus for extending the dynamic range of an integer or fixed-point Fast Fourier Transform (“FFT”) system that may be used in communications devices such as ADSL modems. The disclosed FFT system utilizes a shift control module to increase the effective dynamic range of the FFT implementation by selectively choosing at least one stage of an FFT butterfly implementation in which the outputs of the butterfly stage are not divided to otherwise avoid overflow problems.
Claims1
A method in an FFT system for extending a dynamic range of communication signals in communication devices, comprising the steps of:
- obtaining a communications signal, the communication signal comprising a set of data points, the communication signal having a set of signal characteristics;
- enabling an output division of the communication signal data points, the output division enabled at each output stage of the FFT system during a first communications signal transmission;
- determining a maximum output communication signal sampled during the first signal transmission;
- predicting a maximum output signal during a second signal transmission using the signal characteristics of the communication signal during the first communications signal transmission;
- calculating a number of unnecessary output divisions for each output stage of the FFT system during the second signal transmission, the number of unnecessary output divisions determined from the predicted maximum output signal during a second signal transmission and from the maximum output communication signal sampled during the first signal transmission;
- and
- disabling selectively the output stage division for at least one output stage of the FFT system during the second signal transmission using the number of unnecessary output divisions determined in the calculating step.
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Dependencies are inferred from the claim text.