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US 8,949,061 B2Granted
Method and apparatus for detecting the presence of a DTV pilot tone in a high noise environment
AssigneeWi-LAN, Inc.
InventorsVajira Samarasooriya, Daniel Payer, James S. Wight
Life of this patent
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Abstract
A DTV pilot tone is detected in a noisy environment by computing a power average of Fast Fourier Transform (FFT) output spectra of a received signal, finding a power peak in the averaged outputs, computing an adjustment parameter to center the power peak in a Discrete Fourier Transform bin of the averaged output spectra, applying the adjustment parameter to adjust the received signal, computing a coherent average of FFT output spectra of the adjusted signal, and, testing a power spectrum of the coherent average for the presence of the DTV pilot tone.
Claims23
A method of detecting the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- computing a power average of a plurality of Fast Fourier Transform (FFT) output spectra of a digital baseband signal derived from a TV band channel to create a power averaged output spectrum;
- estimating a power peak in the power averaged output spectrum;
- computing based upon the estimated power peak, an adjustment parameter to adjust the signal to center the power peak in a Discrete Fourier Transform (DFT) bin of the FFT output spectra;
- applying the computed parameter to adjust the signal;
- computing a coherent average of FFT output spectra of the adjusted signal;
- computing a power spectrum of the coherent averaged output spectrum;
- testing the power spectrum for the DTV pilot tone by identifying a peak power in the power spectrum of the coherent averaged output spectrum;
- and
- determining whether the test exceeds a threshold.
6 more elements
Apparatus that detects the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- a spectrum power averager that averages a plurality of output spectra of a Fast Fourier Transform (FFT) of a baseband signal derived from a television band channel to create an averaged output spectrum;
- a peak frequency estimator that estimates a peak power of the averaged output spectrum, determines a frequency of the peak power and computes a frequency adjustment parameter to center the peak power in a Discrete Fourier Transform bin of the output spectra;
- a complex frequency shifter that uses the frequency adjustment parameter to adjust a frequency of the signal to center the peak power in the Discrete Fourier Transform bin;
- a spectrum coherent averager that averages output spectra of a FFT of the baseband signal at the adjusted frequency and computes a power spectrum from the coherent average;
- a peak search algorithm that computes a peak power in the computed power spectrum;
- a noise floor estimator that computes a noise floor around the peak power of the computed power spectrum;
- and
- a pilot tone tester that compares the peak power of the computed power spectrum with the noise floor to determine if the DTV pilot tone has been detected when a threshold has been exceeded.
5 more elements
Apparatus that detects the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- a spectrum power averager that averages output spectra of a Fast Fourier Transform (FFT) of a baseband signal derived from a television band channel;
- a peak frequency estimator that estimates a peak power of the averaged output spectra, determines a frequency of the peak power and computes a frequency adjustment parameter to center the peak power in a Discrete Fourier Transform bin of the FFT output spectrum;
- an analog radio frequency front end which uses the sampling rate adjustment parameter to re-program a high-resolution programmable phase locked loop (PLL) that permits a tuning frequency to be programmed to effect the frequency adjustment;
- a spectrum coherent averager that averages output spectra of a FFT of the baseband signal at the adjusted frequency and computes a power spectrum from the coherent average;
- a peak search algorithm that computes a peak power in the computed power spectrum;
- a noise floor estimator that computes a noise floor around the peak power of the computed power spectrum;
- and
- a pilot tone tester that compares the peak power of the computed power spectrum with the noise floor to determine if the DTV pilot tone has been detected.
5 more elements
Apparatus that detects the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- a spectrum power averager that averages output spectra of a Fast Fourier Transform (FFT) of a baseband signal derived from a television band channel;
- a peak frequency estimator that estimates a peak power of the averaged output spectra, determines a frequency of the peak power and computes a frequency adjustment parameter to center the peak power in a Discrete Fourier Transform bin of the output spectrum;
- a digital mixer that uses the frequency adjustment parameter to re-program a digital phase locked loop or a direct digital synthesizer that permits a mixing frequency to be tuned to effect the frequency adjustment;
- a spectrum coherent averager that averages output spectra of a FFT of the baseband signal at the adjusted frequency and computes a power spectrum from the coherent average;
- a peak search algorithm that computes a peak power in the computed power spectrum;
- a noise floor estimator that computes a noise floor around the peak power of the computed power spectrum;
- and
- a pilot tone tester that compares the peak power of the computed power spectrum with the noise floor to determine if the DTV pilot tone has been detected.
5 more elements
Apparatus that detects the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- a spectrum power averager that averages output spectra of a Fast Fourier Transform (FFT) of a baseband signal derived from a television band channel;
- a peak frequency estimator that estimates a peak power of the averaged output spectra, determines a frequency of the peak power and computes a sampling rate adjustment parameter to center the peak power in a Discrete Fourier Transform bin of the output spectrum;
- a phase locked loop that generates an analog-to-digital sampling clock and uses the sampling rate adjustment parameter to adjust the analog-to-digital sampling clock to effect the sampling rate adjustment;
- a spectrum coherent averager that averages output spectra of a FFT of the baseband signal at the adjusted sampling rate and computes a power spectrum from the coherent average;
- a peak search algorithm that computes a peak power in the computed power spectrum;
- a noise floor estimator that computes a noise floor around the peak power of the computed power spectrum;
- and
- a pilot tone tester that compares the peak power of the computed power spectrum with the noise floor to determine if the DTV pilot tone has been detected.
5 more elements
Apparatus that detects the presence of a digital television (DTV) pilot tone in a high noise environment, comprising:
- a spectrum power averager that averages output spectra of a Fast Fourier Transform (FFT) of a baseband signal derived from a television band channel;
- a peak frequency estimator that estimates a peak power of the averaged output spectra, determines a frequency of the peak power and computes a fractional rate adjustment parameter to center the peak power in a Discrete Fourier Transform (DFT) bin of the output spectrum;
- a fractional sampling rate converter that uses the fractional rate adjustment parameter to adjust the sampling rate to center the peak power in the DFT bin;
- a spectrum coherent averager that averages output spectra of a FFT of the baseband signal at the adjusted sampling rate and computes a power spectrum from the coherent average;
- a peak search algorithm that computes a peak power in the computed power spectrum;
- a noise floor estimator that computes a noise floor around the peak power of the computed power spectrum;
- and
- a pilot tone tester that compares the peak power of the computed power spectrum with the noise floor to determine if the DTV pilot tone has been detected.
5 more elements
Dependencies are inferred from the claim text.