Dither noise source with notched frequency spectrum
AssigneeVisteon Global Technologies, Inc.
InventorsJ. William Whikehart, Terry Robert Altmayer
Life of this patent
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Abstract
A dither signal source generates a dither signal which is spectrally shaped in a desired manner. One or more notches are located at desired frequencies while minimizing the hardware required in a digital signal processor for generating the digital random noise for the dither signal source. The notched dither signal can be added to an analog signal prior to digitization to reduce quantization distortion without adding noise to the frequency range of interest.
Claims12
A dither signal source for generating a dither signal in a digital processing system wherein a digital signal is processed having a sample rate fs, and wherein said dither signal is spectrally shaped, said dither signal source comprising:
- a digital random noise generator producing a digital random noise sequence at a sample rate fn where f n = f s n
- with n equal to an integer;
- and
- a zero-order hold receiving said digital random noise sequence and producing a held output for n samples at said sample rate fs, said held output providing a modified digital random noise sequence having a spectral shape including at least one notch.
A method of generating a spectrally-shaped dither signal in a digital processing system wherein a digital signal is processed having a sample rate fs, said method comprising the steps of:
- generating a pseudo-random noise sequence at a sample rate fn, where f n = f s n
- with n equal to an integer;
- holding said pseudo-random noise sequence in a zero-order hold for n samples at said sample rate fs to provide a modified pseudo-random noise sequence having a spectral shape including at least one notch;
- and
- adding said modified pseudo-random noise sequence to said digital signal.
A digital signal processing AM/FM radio receiver comprising:
- an AM tuner generating an AM IF signal at an AM IF frequency;
- an FM tuner generating an FM IF signal at an FM IF frequency;
- an analog-to-digital converter for digitizing said AM IF signal and said FM IF signal;
- digital processing means for processing said digitized AM and FM IF signals to recover audio information, said processing being performed at a sample rate fs;
- a pseudo-random noise generator producing a digital pseudo-random noise sequence at a sample rate fn where f n = f s n
- with n equal to an integer;
- a zero-order hold receiving said pseudo-random noise sequence and producing a held output for n samples at said sample rate fs, said held output providing a modified pseudo-random noise sequence having a spectral shape including notches for said respective AM IF frequency and said FM IF frequency;
- a digital-to-analog converter generating an analog dither signal in response to said zero-order hold;
- and
- an adder for adding said analog dither signal to said AM IF signal and said FM IF signal prior to digitizing in said analog-to-digital converter.
Dependencies are inferred from the claim text.