Frequency resolution in a digital oscillator
AssigneeMotorola, Inc.
InventorSteven C. Jasper
Life of this patent
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Abstract
A method and means for improving the frequency resolution in a digital oscillator is described. According to the principles of the present invention, a digital oscillator may be comprised of a frequency latch, a phase accumulator, and a ROM based waveform generator. Improved frequency resolution is achieved in the digital oscillator, without increasing ROM size by quantizing the summed output of a dither generator and the phase accumulator before sending the resultant multi-bit signal to a ROM. The contents of the ROM are sequentially addressed with the resultant multi-bit signal. The output of the ROMs comprise digital words corresponding to a desired waveform envelope.
Claims14
A digital oscillator having improved frequency resolution, said digital oscillator comprising:
- (a) latching means for inputting a binary signal which indicates the desired operating frequency for the digital oscillator;
- (b) phase accumulator means coupled to said latching means for generating a sequence of binary words, representing phase, corresponding to the desired operating frequency for the digital oscillator;
- (c) dither generator means for generating a signal comprising random digital noise;
- (d) digital summation means for combining the respective outputs of said phase accumulator means and said digital dither generator means;
- (e) truncating means for selecting the most significant portion of the output of said digital summation means;
- and
- (f) direct ROM look-up means, coupled to the output of said truncating means, for producing a sequential digital signal which corresponds to an oscillating sinusoidal signal of said desired operating frequency.
A method for improving frequency resolution in a digital oscillator, said method comprising the steps of:
- (a) inputting a binary signal which indicates the desired operating frequency for the digital oscillator;
- (b) generating a sequence of binary words, representing phase, corresponding to the desired operating frequency for the digital oscillator;
- (c) generating a digital dither signal comprising random digital noise;
- (d) summing the respective generated phase words and digital dither words;
- (e) selecting the most significant portion of the summed digital phase and dither words;
- and
- (f) producing a sequential digital signal which corresponds to an oscillating sinusoidal signal of said desired frequency, by addressing a ROM lookup means with said selected significant portion of said combined digital phase and dither words.
A method for improving frequency resolution in a digital oscillator, said method comprising the steps of:
- (a) inputting a binary signal which indicates the desired operating frequency for the digital oscillator;
- (b) generating a sequence of binary words, representing phase, corresponding to the desired operating frequency for the digital oscillator;
- (c) generating a digital dither signal comprising random digital noise;
- (d) summing the respective generated phase words and digital dither words;
- (e) selecting the most significant portion of the summed digital phase and dither words;
- and
- (f) producing a sequential digital signal which corresponds to an oscillating sinusoidal signal of said desired frequency, by addressing a factored ROM lookup means with said selected significant portion of said combined digital phase and dither words.
A digital oscillator having improved frequency resolution, said digital oscillator comprising:
- (a) latching means for inputting a binary signal which indicates the desired operating frequency for the digital oscillator;
- (b) phase accumulator means coupled to said latching means for generating a sequence of binary words, representing phase, corresponding to the desired operating frequency for the digital oscillator;
- (c) dither generator means for generating a signal comprising random digital noise;
- (d) digital summation means for combining the respective outputs of said phase accumulator means and said digital dither generator means;
- (e) truncating means for selecting the most significant portion of the output of said digital summation means;
- and
- (f) factored ROM look-up means, coupled to the output of said truncating means, for producing a sequential digital signal which corresponds to an oscillating sinusoidal signal of said desired operating frequency.
Dependencies are inferred from the claim text.