| 摘要 |
A robust tone detector is realized by applying a single taper, which provides a relatively narrow bandwidth filter, to a received signal and, then, performing a Discrete Fourier Transform of the tapered signal. The result of theFourier transform is used to obtain an estimate of energy in the frequency domain of the expected tone. A prescribed selection algorithm based on the relationship of the received signal energy in the time domain and the energy estimate in the frequency domain is used to determine whether a valid tone has been received. Robustness of the tone detector is improved by performing a plurality of Discrete Fourier Transforms of the single tapered version of the received signal at a corresponding plurality of frequencies relative to the nominal frequency of an expected one or more tones. A further improvement in the tone detector is obtained by dynamically adjusting tone acceptance thresholds based on a measure of channel impairments.
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