A Modified Noise Shaper Structure for Digital PWM DACs
Accurate, monotonic digital-to-analog converters (DACs) can be made employing digital pulse-width modulation (DPWM), but excessive internal clock speeds require the use of noise shaping to reduce the signal word length. Some pulse-width modulation types introduce amplitude-to-phase conversion, which when used with a noise shaper, can lead to partial signal cancellation. This problem is examined, and modified noise shapers which eliminate this cancellation are proposed. Software simulation is used to compare the performance of the new noise shapers with traditional structures. Results show that the modified noise shaper will eliminate this problem in DPWM DACs which employ noise shaping.
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