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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).
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 ...
On the contrary, delta modulation and delta-sigma modulation are random processes [clarification needed] that produces a continuous spectrum without distinct harmonics. While intersective PWM uses a fixed period but a varying duty cycle, the period of delta and delta-sigma modulated PWMs varies in addition to their duty cycle.
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.
Bit depth affects bit rate and file size. Bits are the basic unit of data used in computing and digital communications. Bit rate refers to the amount of data, specifically bits, transmitted or received per second. In MP3 and other lossy compressed audio formats, bit rate describes the amount of information used to encode an audio signal.
English: Delta-sigma modulation loop model with quantization noise in the Laplace (s) domain. Integration become 1/s, and the quantization process can be modeled as simply adding noise. Integration become 1/s, and the quantization process can be modeled as simply adding noise.
English: Simple circuit performing delta-sigma modulation on an input 20 kHz sine wave s(t). An ideal op amp integrator using s(t) and p(t) produces ε(t), which can be quantized and sampled by an ideal D flip flop to produce a pulse density modulation result p(t), which used as negative feedback.