Hardware-efficient phase-to-amplitude mapping design for direct digital frequency synthesizers
First Claim
1. A phase-to-amplitude sinusoidal mapping circuit using linear approximation, comprising:
- A base decoder that decodes a number of MSBs of a digital phase angle to generate a base value of a sinusoidal amplitude for the phase angle;
A controller that maps the MSBs to a segment number in a quadrant of the sinusoid to select at least one signed shift value for that segment number;
At least one shifter block that shifts the remaining LSBs of the phase angle by the corresponding shift value; and
An adder that adds the at least one signed and shifted LSBs to the base value to provide an approximate sinusoidal amplitude for the phase angle.
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Abstract
A hardware-efficient mapping circuit uses a base decoder to decode the control signal (the most significant bits “MSBs” of the phase angle) to provide a base value. A controller maps the control signal to a segment number to down select signed shift values from the control signal. Shifter blocks shift the data signal (the least significant bits “LSBs” of the phase angle) by the respective shift values. The shifted data signals are added/subtracted from the base value to approximate a sinusoidal amplitude for the phase angle. Down selection by a controller allows the shifter blocks to be implemented with narrow band multiplexers, which conserves both chip space and power.
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Citations
23 Claims
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1. A phase-to-amplitude sinusoidal mapping circuit using linear approximation, comprising:
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A base decoder that decodes a number of MSBs of a digital phase angle to generate a base value of a sinusoidal amplitude for the phase angle; A controller that maps the MSBs to a segment number in a quadrant of the sinusoid to select at least one signed shift value for that segment number; At least one shifter block that shifts the remaining LSBs of the phase angle by the corresponding shift value; and An adder that adds the at least one signed and shifted LSBs to the base value to provide an approximate sinusoidal amplitude for the phase angle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A phase-to-amplitude sinusoidal mapping circuit using linear approximation, comprising:
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A base decoder that decodes a number of MSBs of a digital phase angle to generate a base value of a sinusoidal amplitude for the phase angle; A controller that maps the MSBs to a select signal corresponding to a shift value and a sign; A shifter block comprising a plurality of N-port multiplexers in which each input port corresponds to a different shift value, said multiplexers configured to receive the remaining LSBs at their input ports down shifted from one multiplexer to the next and, in response to the select signal, to pass the down shifted LSB at the selected input port to an output port and together to pass the remaining LSBs right shifted by a shift value associated with the selected input port; and An adder that sums the shifted LSBs and the base value according to the sign to provide an approximate sinusoidal amplitude for the phase angle. - View Dependent Claims (13, 14, 15)
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16. A Direct Digital Frequency Synthesizer (DDFS), comprising:
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A phase accumulator that calculates digital phase angles from a signal representing a sinusoid function defined by a plurality of linear segments; A phase-to-amplitude mapping circuit including, A base decoder that decodes a number of MSBs of the phase angle to generate a base value of a sinusoidal amplitude for the phase angle; A controller that maps the MSBs to a segment number in the quadrant of the sinusoid to select a plurality of signed shift value for that segment number; A plurality of shifter blocks that shift the remaining LSBs of the phase angle by the corresponding shift values; and An adder that adds the plurality of signed and shifted LSBs to the base value to provide an approximate sinusoidal amplitude for the phase angle; and A digital-to-analog converter that receives digital information and converts the approximate sinusoidal amplitude to an analog value. - View Dependent Claims (17, 18, 19, 20)
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21. A method of direct digital frequency synthesis, comprising:
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calculating digital phase angles from a signal representing a sinusoid function defined by a plurality of linear segments; decoding a number of MSBs of each said digital phase angle to generate a base value of a sinusoidal amplitude for the phase angle; mapping the MSBs to a segment number in a quadrant of the sinusoid to select at least one signed shift value for that segment number; shifting the remaining LSBs of the digital phase angle by the at least one shift value; adding at least one signed and shifted LSBs to the base value to provide an approximate sinusoidal amplitude for each said phase angle; and converting the sinusoidal amplitude for each said phase angle to an analog value to synthesize an analog signal. - View Dependent Claims (22, 23)
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Specification