System for generating correction signals for use in forming low distortion analog signals

A signal generator comprising:

• 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.

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:

• 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.

A method of generating a correction signal from a data signal for forming a low distortion analog signal, comprising the steps of:

• 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.

A method of making a low noise analog signal of a given frequency, which comprises:

• 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.

An analog signal generator comprising:

• 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.