Delta-Sigma Modulation Techniques in Analog-to-Digital Conversion

Delta-sigma modulation is a cornerstone approach for high-resolution analogue-to-digital conversion, combining oversampling with active noise shaping to achieve superior signal fidelity. In these systems, the analogue input is fed into one or more integrators, a coarse quantiser and a feedback digital-to-analogue converter in a closed loop. The quantisation noise is pushed towards higher frequencies by designing the noise-transfer function, allowing in-band performance to be dramatically improved once the signal is decimated and filtered. Architectures range from first-order single-loop modulators suitable for low-power sensing to high-order continuous-time or discrete-time designs delivering multi-MHz bandwidths and sub-noise-floor resolution. Key practical challenges include finite amplifier gain, clock jitter, thermal noise, distortion and mismatches, which are addressed through integrator-sharing topologies, compensation techniques, digital calibration, sampling-noise cancellation and variation-aware circuit methods. Through co-design of analogue front-ends and digital back-ends, modern delta-sigma converters achieve figures of merit approaching fundamental thermodynamic limits, finding deployment in precision instrumentation, biomedical monitoring, wireless communications and the Internet-of-Things.

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Delta-Sigma Modulation Techniques in Analog-to-Digital Conversion publication trend

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Technical terms

Delta-Sigma Modulation: A technique that oversamples the input and shapes quantisation noise to achieve high resolution within a target bandwidth.

Oversampling Ratio (OSR): The factor by which the sampling frequency exceeds twice the signal bandwidth, critical for noise reduction.

Noise Shaping: The process of filtering quantisation noise so that its power is transferred out of the signal band.

Decimation Filter: A digital filter that reduces the converter’s sample rate to the desired output rate while rejecting out-of-band noise.

Signal-to-Noise-and-Distortion Ratio (SNDR): A performance metric combining signal quality, noise and distortion into a single figure of merit.

References

1. L${}_{\text{2}}$min${}^{\text{2/2s}}$: Efficient Linear Reconstruction Filter for Incremental Delta-Sigma ADCs. IEEE Transactions on Signal Processing (2023).
2. Ultralow-Power Inverter-Based Delta-Sigma Modulator for Wearable Applications. IEEE Access (2024).
3. A 79.2-μW 19.5-kHz-BW 94.8-dB-SNDR Fully Dynamic DT ΔΣ ADC Using CLS-Assisted FIA With Sampling Noise Cancellation. IEEE Transactions on Circuits & Systems II Express Briefs (2023).