System for generating correction signals for use in forming low distortion analog signals
First Claim
1. A signal generator for generating a correction signal from a digital data signal for forming a low distortion analog signal, comprising:
- a data signal source for outputting a segment of said digital data signal;
a storage device having an input coupled to the output of said data signal source for storing said segment of said digital data signal;
a distortion estimator having an input coupled to the output of said data signal source and operable to determine signal distortion characteristics of said segment of said digital data signal when said segment is repetitively read out from said storage device and converted to an analog data signal;
a correction signal encoder adapted to encode the output of said distortion estimator into a segment of digital correction signal having opposite phase and increased amplitude form said signal distortion phase and amplitude of said output of said distortion estimator, and having an output coupled to said input of said storage device for outputting said segment of digital correction signal to said storage device.
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Abstract
A method and apparatus for generating correction signals for use in forming low distortion analog signals. A digital representation of a desired analog waveform is encoded into a digital data signal which is outputted to memory. A digital correction signal is encoded, having an opposite phase and increased amplitude from the signal distortion which it is determined will occur when the digital data signal is repetitively read out of memory and decoded. This digital correction signal is outputted to memory. The digital data and correction signals are repetitively and synchronously read out of memory into a decoder. The decoder converts both digital signals into analog signals, so that the analog correction signal may superpose on the distortion in the analog data signal, resulting in a low distortion analog signal.
105 Citations
34 Claims
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1. A signal generator for generating a correction signal from a digital data signal for forming a low distortion analog signal, comprising:
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a data signal source for outputting a segment of said digital data signal; a storage device having an input coupled to the output of said data signal source for storing said segment of said digital data signal; a distortion estimator having an input coupled to the output of said data signal source and operable to determine signal distortion characteristics of said segment of said digital data signal when said segment is repetitively read out from said storage device and converted to an analog data signal; a correction signal encoder adapted to encode the output of said distortion estimator into a segment of digital correction signal having opposite phase and increased amplitude form said signal distortion phase and amplitude of said output of said distortion estimator, and having an output coupled to said input of said storage device for outputting said segment of digital correction signal to said storage device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A signal generator comprising:
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a waveform generator for generating a digital representation of a periodic waveform; a first encoder for encoding the output of said waveform generator into a data signal digital bitstream segment corresponding to one period of said periodic waveform; a distortion estimator for determining the phase and amplitude of signal distortion within a frequency band of interest created by repetitively decoding said data signal digital bitstream segment into an analog signal, and generating a distortion digital datastream having an amplitude increased by a scale factor greater than one from said amplitude, and an opposite phase from said phase, of said signal distortion; and a second encoder for encoding said distortion digital datastream into a correction signal digital bitstream segment corresponding to the same period of said periodic waveform as said data signal digital bitstream segment. - View Dependent Claims (14)
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15. A method of generating a correction signal for forming an analog signal having low distortion within a frequency band of interest, comprising the steps of:
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outputting from a data signal source a segment of digital data signal having known frequency, amplitude and phase characteristics and having, when repetitively decoded, a signal distortion having frequency, amplitude, and phase characteristics; determining frequency, amplitude, and phase characteristics within said frequency band of interest which said signal distortion of said segment of digital data signal will have when it is repetitively decoded; and encoding said determined characteristics into a segment of a digital correction signal of opposite phase and increased amplitude from said determined characteristics. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of generating a correction signal from a data signal for forming a low distortion analog signal, comprising the steps of:
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generating a digital representation of a periodic waveform; computationally encoding said digital representation of a periodic waveform into a data signal digital bitstream segment corresponding to one period of said periodic waveform, having known frequency, amplitude and phase characteristics, and having, when repetitively decoded, a signal distortion having frequency, amplitude, and phase characteristics; storing said data signal digital bitstream segment in a memory; computationally determining frequency, phase and amplitude characteristics within a frequency band of interest which said signal distortion of said data signal digital bitstream segment will have when said data signal digital bitstream segment is repetitively decoded into an analog signal; computationally encoding said determined frequency, phase and amplitude characteristics into a correction signal digital bitstream segment corresponding to approximately the same period of said periodic waveform as said data signal digital bitstream segment, and having increased amplitude by a scale factor greater than one and opposite phase from said determined frequency, phase and amplitude characteristics; and storing said correction signal digital bitstream segment in said memory. - View Dependent Claims (25, 26)
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27. A method of making a low noise analog signal of a given frequency, which comprises:
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transforming a time-domain digital data signal into the frequency domain to include a first frequency component corresponding to said given frequency and at least one other frequency component corresponding to noise; inverse transforming at least one of said other frequency components within a frequency band of interest into a time domain digital correction signal; and storing said digital data signal and digital correction signal. - View Dependent Claims (28, 29, 30, 31, 32)
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33. An analog signal generator comprising:
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an encoder for encoding a first digital representation of a period waveform into a data signal digital datastream and a correction signal digital datastream; a memory for storing the two digital datastreams; and a digital to analog decoder for synchronously reading the two datastreams out of the memory, combining the two datastreams so as to correct the data signal digital datastream for distortions, and outputting a corrected analog signal. - View Dependent Claims (34)
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Specification