Frequency extension of harmonic signals
First Claim
1. A method of extending harmonics of a band-limited harmonic signal, the method comprising:
- transforming a band-limited harmonic signal from the time domain to the frequency domain to obtain a complex spectrum of the band-limited harmonic signal;
performing a non-linear transformation on the complex spectrum of the band-limited harmonic signal in the frequency domain to extend harmonic content of the band-limited harmonic signal to frequencies outside the limited frequency band of the band-limited harmonics signal; and
inverse transforming the extended complex spectrum of the band-limited harmonic signal back into the time domain.
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Abstract
A system and methods are provided for extending the frequency bandwidth of a harmonic signal. Harmonic content of a band-limited signal is extended to frequencies outside the signal'"'"'s passband by performing a non-linear transformation on the complex spectrum of the band-limited signal in the frequency domain. The non-linear transformation may be accomplishes by a linear convolution of the complex spectrum with itself. A system for extending the frequency bandwidth of a harmonic signal includes a signal processor with a forward transform module for transforming a time domain signal into the frequency domain, a non-linear transform module for performing the non-linear transformation on the complex spectrum of the harmonic signal, and a reverse transform module for transforming the extended spectrum of the harmonic signal back into the time domain.
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Citations
32 Claims
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1. A method of extending harmonics of a band-limited harmonic signal, the method comprising:
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transforming a band-limited harmonic signal from the time domain to the frequency domain to obtain a complex spectrum of the band-limited harmonic signal;
performing a non-linear transformation on the complex spectrum of the band-limited harmonic signal in the frequency domain to extend harmonic content of the band-limited harmonic signal to frequencies outside the limited frequency band of the band-limited harmonics signal; and
inverse transforming the extended complex spectrum of the band-limited harmonic signal back into the time domain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15)
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11. A harmonic extension method comprising:
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receiving a band-limited harmonic signal having significant signal energies at regular frequency intervals within a limited frequency band defined by a passband lower frequency limit and a passband upper frequency limit;
transforming the band-limited harmonic signal from the time domain to the frequency domain to obtain a complex spectrum of the received band-limited harmonic signal;
performing a non-linear transformation of the complex spectrum of the received band-limited harmonic signal in the frequency domain to generate an extended spectrum having harmonic energy at at least one harmonic frequency at which harmonic energy was absent in the received band limited harmonic signal; and
transforming the extended spectrum into the time domain. - View Dependent Claims (12, 13, 14, 16, 17, 18, 19, 20)
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21. A system for extending harmonics of a band-limited harmonic signal, the system comprising:
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means for receiving a band-limited harmonic signal; and
a signal processor having a forward transform module for transforming the received band-limited harmonic signal from the time domain to the frequency domain to generate a complex spectrum of the band-limited signal; and
a harmonic generation module for performing a non-linear transformation of the complex spectrum of the band-limited signal in the frequency domain to create a harmonically extended spectrum of the band-limited harmonics signal; and
a reverse transform module for transforming the harmonically extended spectrum of the band-limited harmonics signal back to the time domain. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A system for extending harmonics and spectral envelope of a band-limited harmonic signal and combining the extended signal with the original band-limited signal, the system comprising:
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means for receiving a band-limited harmonic signal; and
a signal processor having a forward transform module for transforming the received band-limited harmonic signal from the time domain to the frequency domain to generate a complex spectrum of the band-limited signal; and
a harmonic generation module for performing a non-linear transformation of the complex spectrum of the band-limited signal in the frequency domain to create a harmonically extended spectrum of the band-limited harmonics signal; and
a spectral envelope extender module to ensure the spectral envelope of the extended harmonics is complimentary to that of the original band-limited signal; and
a combiner module to combine the harmonic extended spectrum with the original band-limited spectrum; and
a reverse transform module for transforming the final frequency extended harmonic spectrum back to the time domain. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification