System and method employing a reduced NCO lookup table
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorRichard Hellberg
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Abstract
A system and method for reducing the computational complexity of the calculations performed by a Numerically Controlled Oscillator (NCO). Through exploitation of mathematical symmetries and other techniques, the size of a lookup table of sinusoidal values employed by the NCO to approximate sinusoids may be reduced by the combination of different frequency shifts.
Claims28
A numerically controlled oscillator for combining frequencies depending upon input numerical data, said numerically controlled oscillator comprising:
- a combiner for combining a first and a second set of frequencies for said input numerical data, said first set of frequencies being spaced apart by a first shift amount, and said second set frequencies being spaced apart by a second shift amount, the numbers of frequencies within said first and second sets being coprime with respect to each other;
- and output means for outputting an output oscillation frequency based upon the combination of frequencies within said first and second sets.
A numerically controlled oscillator system whose output oscillation frequency is controlled depending upon input numerical data, said numerically controlled oscillator system comprising:
- a first frequency shifting means for shifting an input frequency within a first set of frequencies, said first set of frequencies being spaced apart by a first shift amount;
- a second frequency shifting means for shifting said input frequency within a second set of frequencies, said second set of frequencies being spaced apart by a second shift amount, the numbers of frequencies within said first and second sets being coprime with respect to each other, whereby each output oscillation frequency is a combination of frequencies within said first and second sets.
A method for modulating an input frequency through a numerically controlled oscillator, said method comprising the steps of:
- shifting said input frequency within a first set of frequencies, said first set of frequencies being spaced apart by a first shift amount;
- shifting said input frequency within a second set of frequencies, said second set of frequencies being spaced apart by a second shift amount, the numbers of frequencies within said first and second sets being coprime with respect to each other;
- and
- forming, by said numerically controlled oscillator, an output oscillation frequency, said output oscillation frequency being a combination of frequencies within said first and second sets.
Dependencies are inferred from the claim text.