A Different View of Sigma-Delta Modulators Under the Lens of Pulse Frequency Modulation (2311.06983v4)
Abstract: The fact that VCO-ADCs produce noise-shaped quantization noise suggests that a link between frequency modulation and Sigma-Delta modulation should exist. The connection between a VCO-ADC and a first-order Sigma-Delta modulator has been already explained using Pulse Frequency Modulation. In this paper, we attempt to extend the theory based on Pulse Frequency Modulation to a generic Sigma-Delta modulator. We show that this link between Sigma-Delta modulation and Pulse Frequency Modulation relies in a sampling invariance property that defines the equivalence between both entities. This novel point of view, allows to go beyond the white quantization noise model of a Sigma-Delta modulator, revealing the origin of some nonlinear phenomena. We first predict spurious tones which cannot be explained by circuit non linearity. Multi-bit and single bit modulators are shown to belong to a same generic class of systems. Finally, quantizer overload is analyzed using our model. The results are applied to Continuous-Time Sigma-Delta modulators of orders one, two and three and then extended to a generic case.
- C. B. Brahm, “Feedback Integrating System,” US Patent 3,192,371, September 19, 1961.
- H. Inose, Y. Yasuda, and J. Murakami, “A Telemetering System by Code Modulation - ΔΔ\Deltaroman_Δ- ΣΣ\Sigmaroman_ΣModulation,” IRE Transactions on Space Electronics and Telemetry, vol. SET-8, no. 3, pp. 204–209, 1962.
- J. Candy, “A Use of Double Integration in Sigma Delta Modulation,” IEEE Transactions on Communications, vol. 33, no. 3, pp. 249–258, 1985.
- R. Gray, “Spectral analysis of quantization noise in a single-loop sigma-delta modulator with DC input,” IEEE Transactions on Communications, vol. 37, no. 6, pp. 588–599, 1989.
- R. Schreier, M. Goodson, and B. Zhang, “An algorithm for computing convex positively invariant sets for delta-sigma modulators,” IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, vol. 44, no. 1, pp. 38–44, 1997.
- O. Feely, “Nonlinear dynamics of sigma-delta modulation,” in [1991] Proceedings of the 34th Midwest Symposium on Circuits and Systems, 1991, pp. 760–763 vol.2.
- S. Ardalan and J. Paulos, “An analysis of nonlinear behavior in delta - sigma modulators,” IEEE Transactions on Circuits and Systems, vol. 34, no. 6, pp. 593–603, 1987.
- R. Schreier, “An empirical study of high-order single-bit delta-sigma modulators,” IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, vol. 40, no. 8, pp. 461–466, 1993.
- R. Schreier and B. Zhang, “Delta-sigma modulators employing continuous-time circuitry,” IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, vol. 43, no. 4, pp. 324–332, 1996.
- M. Hovin, A. Olsen, T. Lande, and C. Toumazou, “Delta-sigma converters using frequency-modulated intermediate values,” in 1995 IEEE International Symposium on Circuits and Systems (ISCAS), vol. 1, 1995, pp. 175–178 vol.1.
- M. Z. Straayer and M. H. Perrott, “A 12-Bit, 10-MHz Bandwidth, Continuous-Time ΣΔΣΔ\Sigma\Deltaroman_Σ roman_Δ ADC With a 5-Bit, 950-MS/s VCO-Based Quantizer,” IEEE Journal of Solid-State Circuits, vol. 43, no. 4, pp. 805–814, April 2008.
- G. G. Gielen, L. Hernandez, and P. Rombouts, “Time-Encoding Analog-to-Digital Converters: Bridging the Analog Gap to Advanced Digital CMOS-Part 1: Basic Principles,” IEEE Solid-State Circuits Magazine, vol. 12, no. 2, pp. 47–55, 2020.
- C. M. Zierhofer, “Frequency Modulation and First-Order Delta Sigma Modulation: Signal Representation With Unity Weight Dirac Impulses,” IEEE Signal Processing Letters, vol. 15, pp. 825–828, 2008.
- L. Hernandez and E. Gutierrez, “Analytical Evaluation of VCO-ADC Quantization Noise Spectrum Using Pulse Frequency Modulation,” IEEE Signal Processing Letters, vol. 22, no. 2, pp. 249–253, FEB 2015.
- E. Gutierrez, L. Hernandez, F. Cardes, and P. Rombouts, “A Pulse Frequency Modulation Interpretation of VCOs Enabling VCO-ADC Architectures With Extended Noise Shaping,” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 65, no. 2, pp. 444–457, Feb 2018.
- V. Medina, S. Paton, E. Gutierrez, and L. Hernandez, “A Model of Continuous-Time Sigma Delta Modulation Based on Pulse Frequency Encoding,” in 2020 IEEE International Symposium on Circuits and Systems (ISCAS), 2020, pp. 1–5.
- J. Bayly Elliott, “Spectral Analysis of Pulse Frequency Modulation in the Nervous Systems,” IEEE Transactions on Biomedical Engineering, vol. BME-15, no. 13, pp. 257–265, Oct. 1968.
- E. Fitch, “The spectrum of modulated pulses,” Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication, vol. 94, no. 13, pp. 556–564, Mar.-Apr. 1947.
- J. Carson, “Notes on the Theory of Modulation,” Proceedings of the Institute of Radio Engineers, vol. 10, no. 1, pp. 57–64, 1922.
- C. M. Zierhofer, “Quantization Noise as Superposition of Frequency-Modulated Sinusoids,” IEEE Signal Processing Letters, vol. 16, no. 11, pp. 933–936, 2009.
- T. Claasen and A. Jongepier, “Model for the power spectral density of quantization noise,” IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 29, no. 4, pp. 914–917, 1981.
- S. Pavan, “Continuous-Time Delta-Sigma Modulator Design Using the Method of Moments,” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 61, no. 6, pp. 1629–1637, 2014.
- F. Gerfers, M. Ortmanns, and Y. Manoli, “A 1.5-V 12-bit power-efficient continuous-time third-order ΣΔΣΔ\Sigma\Deltaroman_Σ roman_Δ modulator,” IEEE Journal of Solid-State Circuits, vol. 38, no. 8, pp. 1343–1352, 2003.
- L. Hernandez and E. Prefasi, “Analog-to-digital conversion using noise shaping and time encoding,” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 55, no. 7, pp. 2026–2037, 2008.
- B. Drost, M. Talegaonkar, and P. K. Hanumolu, “A 0.55V 61dB-SNR 67dB-SFDR 7MHz 4th-order Butterworth filter using ring-oscillator-based integrators in 90nm CMOS,” in 2012 IEEE International Solid-State Circuits Conference, 2012, pp. 360–362.
- L. Hernandez, E. Gutierrez, and F. Cardes, “Frequency-encoded integrators applied to filtering and sigma-delta modulation,” in 2016 IEEE International Symposium on Circuits and Systems (ISCAS), 2016, pp. 478–481.
- V. Medina, D. Loi, P. Rombouts, and L. Hernandez, “Analysis of in-band Spurious Tones of VCO-based Analog Filters and Mitigation Techniques,” in 2023 IEEE International Symposium on Circuits and Systems (ISCAS), 2023, pp. 1–5.