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Delta-sigma (ΔΣ; or sigma-delta, ΣΔ) modulation is an oversampling method for encoding signals into low bit depth digital signals at a very high sample-frequency as part of the process of delta-sigma analog-to-digital converters (ADCs) and digital-to-analog converters (DACs).
Sinc N filters are commonly used with delta-sigma modulation ADCs just prior to downsampling to the desired output data rate (ODR) of . A sinc N filter's frequency response will lie under a –20·N dB per decade envelope, so higher orders have steeper roll off for cutting out more high frequency noise, but will also have a lower -3 dB frequency .
To achieve high signal-to-noise ratio, delta modulation must use oversampling techniques, that is, the analog signal is sampled at a rate several times higher than the Nyquist rate. Derived forms of delta modulation are continuously variable slope delta modulation, delta-sigma modulation, and differential modulation.
A delta-sigma ADC (also known as a sigma-delta ADC) is based on a negative feedback loop with an analog filter and low resolution (often 1 bit) but high sampling rate ADC and DAC. The feedback loop continuously corrects accumulated quantization errors and performs noise shaping : quantization noise is reduced in the low frequencies of interest ...
SACD, 1-bit delta-sigma modulation process known as Direct Stream Digital, co-developed by Sony and Philips. 5,644,800 Hz Double-Rate DSD, 1-bit Direct Stream Digital at 2× the rate of the SACD. Used in some professional DSD recorders. 11,289,600 Hz Quad-Rate DSD, 1-bit Direct Stream Digital at 4× the rate of the SACD. Used in some uncommon ...
A 1-bit DAC (sometimes called Bitstream converter by Philips) is a consumer electronics marketing term describing an oversampling digital-to-analog converter (DAC) that uses a digital noise shaping delta-sigma modulator operating at many multiples of the sampling frequency that outputs to an actual 1-bit DAC (which could be fully differential to minimize crosstalk). [1]
Similarly, high-speed pulse-width modulation or delta-sigma modulation produces outputs that only assume two states, but the effective output swings through a continuous range of motion. These complications can be avoided by using a different nonlinear control design method that produces a continuous controller.
Delta-sigma modulation – Another (feedback) method of encoding a continuous range of values in a signal that rapidly switches between two states (i.e., a kind of specialized sliding-mode control) Pulse-density modulation – A generalized form of delta-sigma modulation.