Method and apparatus for producing a pulse width modulated signal
AssigneeMotorola, Inc.
InventorsCesar Pascual, William J. Roeckner
Life of this patent
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Abstract
A method and apparatus to produce a pulse width modulated (PWM) signal from pulse code modulated (PCM) data. In one embodiment, a crossing point of an analog signal with the ramp portion of a sawtooth waveform is approximated by first extrapolating, or projecting, a line between two adjacent sample points across other sample points to produce an estimate of the crossing point. A magnitude difference between a crossing point of the extrapolated line and a sample point magnitude on each side of the crossing point is determined. The magnitude difference, multiplied by an empirically determined constant, is added to the estimate. A PWM signal is then produced using the estimate for the crossing point.
Claims22
A method of converting a pulse code modulated data stream to produce a pulse width modulated signal, the method comprising:
- receiving the pulse code modulated data stream;
- interpolating the pulse code modulated data stream to produce an upsampled pulse code modulated data stream;
- for a set of samples of the upsampled pulse code modulated data stream, converting the upsampled pulse code modulated data stream to digital pulse width modulated data including a data point having a sample time between two adjacent samples of the set of samples, the data point determined based on at least one magnitude difference value relative to at least one sample of the set of samples other than the two adjacent samples, wherein the magnitude difference value is a difference in signal magnitude between the at least one sample and a linearly extrapolated data point based on the two adjacent samples;
- and
- producing the pulse width modulated signal in response to the digital pulse width modulated data.
An apparatus for converting a pulse code modulated data stream to a pulse width modulated signal, the apparatus comprising:
- an interpolator to receive the pulse code modulated data stream and to produce an upsampled pulse code modulated data stream;
- an approximating natural sampling module to, for asset of samples of the upsampled pulse code modulated data stream, convert the upsampled pulse code modulated data stream to digital pulse width modulated data
- using an additional data point having a sample time between two adjacent samples of the set of samples, the additional data point computed based on at least one signal magnitude difference value relative to at least one sample of the set of samples other than the two adjacent samples, wherein the magnitude difference value is a difference in signal magnitude between the at least one sample and a linearly extrapolated data point based on the two adjacent samples;
- and
- a pulse width modulation generator to produce the pulse width modulated signal in response to the digital pulse width modulated data.
A method of producing a pulse width modulated signal, the method comprising:
- receiving a pulse code modulated data stream;
- for a set of samples of the pulse code modulated data stream, converting the pulse code modulated data stream to digital pulse width modulated data having at least one data point computed based on a value that indicates a curvature of an analog signal corresponding to the pulse code modulated data stream, the value determined without performing a polynomial equation root-finding operation, wherein the value is a difference in signal magnitude between the at least one sample and a linearly extrapolated data point based on the two adjacent samples;
- and
- producing the pulse width modulated signal in response to the digital pulse width modulated data.
A method of converting a pulse code modulated data stream to produce a pulse width modulated signal, the method comprising:
- interpolating the pulse code modulated data stream to produce an upsampled pulse code modulated data stream;
- for a set of samples of the upsampled pulse code modulated data stream, converting the upsampled pulse code modulated data stream to digital pulse width modulated data having a computed data point with a sample time between two adjacent samples of the set of samples, the data point determined based on a value that indicates a curvature of an analog signal corresponding to the upsampled pulse code modulated data stream, the value determined using a linear operation;
- determining a second data point having a sample time between the two adjacent samples of the set of samples;
- producing the pulse width modulated signal in response to the digital pulse width modulated data.
A method of converting a pulse code modulated data stream to produce a pulse width modulated signal, the method comprising:
- interpolating the pulse code modulated data stream to produce an upsampled pulse code modulated data stream;
- for a set of samples of the upsampled pulse code modulated data stream, converting the upsampled pulse code modulated data stream to digital pulse width modulated data having a computed data point with a sample time between two adjacent samples of the set of samples, the data point determined based on a value that indicates a curvature of an analog signal corresponding to the upsampled pulse code modulated data stream, the value determined using a linear operation, wherein the value is derived based on a first curvature estimate at a first sample of the set of samples and a second curvature estimate at a second sample of the set of samples;
- and
- producing the pulse width modulated signal in response to the digital pulse width modulated data.
A method of converting a pulse code modulated data stream to produce a pulse width modulated signal, the method comprising:
- interpolating the pulse code modulated data stream to produce an upsampled pulse code modulated data stream;
- for a set of samples of the upsampled pulse code modulated data stream, converting the upsampled pulse code modulated data stream to digital pulse width modulated data having a computed data point with a sample time between two adjacent samples of the set of samples, the data point determined based on a value that indicates a curvature of an analog signal corresponding to the upsampled pulse code modulated data stream, the value determined using a linear operation;
- adjusting the value using a curvature adjusting mapping function;
- and
- producing the pulse width modulated signal in response to the digital pulse width modulated data.
Dependencies are inferred from the claim text.