Apparatus and method of generating numerically controlled oscillator signals
AssigneeNational Semiconductor Corporation
InventorsDavid Potson, Mark F. Rives
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Abstract
An apparatus according to a preferred embodiment of the present invention includes two memories each storing different octants of a sine (or cosine) waveform. The sine and cosine waveforms may be concurrently generated by alternately accessing each memory in succession. It is unnecessary to access one memory concurrently, so that both waveforms may be concurrently generated without requiring either two accesses to the same memory or a doubled memory size.
Claims31
A numerically controlled oscillator for providing N number of phase-shifted oscillator outputs, each of which represents a same output waveform shifted in phase, said oscillator comprising:
- N number of storage elements, where N is at least two, with each of the storage elements storing data indicative of a different phase segment of the output waveform, with the phase segment being equal to 1/Nth of a quadrant of the output waveform;
- addressor means for reading the N number of storage elements to provide N number of storage element outputs, with each of the N number of storage element outputs corresponding only to one of the phase segments;
- and
- processor means for receiving the N number of storage element outputs and for producing the N number of phase-shifted oscillator outputs based upon the storage element outputs.
A circuit for generating N number of numerically controlled phase-shifted oscillator outputs, where N is at least two, said circuit comprising:
- N number of storage elements:
- addressor means for reading out each of the N number of storage elements during sequential output time periods, with each of the output time periods corresponding to only 1/(4·N) of a cycle of a waveform represented by one of the oscillator outputs, so as to produce N number of storage element outputs for each the output time periods;
- and
- processor means for producing each of the N number of phase-shifted oscillator outputs from a separate one of the storage element outputs during each of the output time periods.
A numerically controlled oscillator for providing first and second phase-shifted oscillator outputs, said oscillator comprising:
- two storage elements, with each of the storage elements storing data indicative of one of the phase-shifted oscillator outputs during a different phase segment of the one of the phase-shifted oscillator outputs, with the phase segment equal to one octant of the one of the phase-shifted oscillator outputs;
- addressor means for reading the storage elements to provide first and second storage element outputs, with each of the first and second storage element outputs corresponding to only one of the phase segments;
- and
- processor means for producing each of the first and second phase-shifted oscillator outputs based upon the first and second storage element outputs.
A method of producing N number of phase-shifted oscillator outputs, where N is at least two, comprising:
- storing N number of sets of data, with each of the sets of data including data indicative of one of the phase-shifted oscillator outputs during a different phase segment of the one of the phase-shifted oscillator outputs, with the phase segment equal to 1/Nth of a quadrant of a waveform represented by the one of the phase-shifted oscillator outputs;
- accessing the N number of sets of stored data to provide N number of storage element outputs;
- and
- processing the N number of storage element outputs to produce the N number of phase-shifted oscillator outputs.
A method of producing N number of phase-shifted oscillator outputs, where N is at least two, comprising:
- storing N number of sets of data;
- accessing the N number of sets of stored data to provide N number of storage element outputs;
- and
- processing, during each output time period of a sequence of the output time periods, a single one of the N number of storage element outputs is used to produce a single one of the N number of phase-shifted outputs, with each of the output time periods corresponding to 1/Nth of a quadrant of a waveform that represents one of the phase-shifted oscillator outputs, so that all of the N number of storage element outputs are used over the sequence to produce all of the N number of phase-shifted oscillator outputs.
Dependencies are inferred from the claim text.