Coded data generation or conversion – Analog to or from digital conversion – Digital to analog conversion
Reexamination Certificate
2007-04-24
2007-04-24
Barnie, Rexford (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Digital to analog conversion
Reexamination Certificate
active
11428210
ABSTRACT:
The signal processing system includes a pulse width modulator (PWM) that receives a quantizer output signal from a delta sigma modulator. Each quantizer output signal represents one of N quantization levels. For at least one of the quantization levels, the PWM can generate multiple, different PWM patterns. Thus, each quantization level in at least a subset of the N quantization levels is associated with at least two PWM patterns. In at least one embodiment, the subset of quantization levels represents the quantization of low level samples of a quantizer input signal. By associating multiple PWM patterns to at least the subset of the quantization levels, the pulse edges of the PWM patterns in a frame are shifted in time with respect to subsequent PWM patterns, which spreads the spectrum of harmonic frequencies of the PWM output signal. Spreading the spectrum of harmonic frequencies of the PWM output signal can reduce electromagnetic interference (EMI).
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Gaboriau Johann
Melanson John L.
Barnie Rexford
Chambers Kent B.
Cirrus Logic Inc.
Hamilton & Terrile LLP
Lauture Joseph
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