Analytical Evaluation of VCO-ADC Quantization Noise Spectrum Using Pulse Frequency Modulation

Oversampled ADCs based on voltage-controlled oscillators have been analyzed using statistical models inherited from sigma-delta modulation. This letter shows that the discrete Fourier transform of a VCO-ADC output sequence can be calculated analytically for single tone inputs. The calculation is based on the transformation of the VCO output into a pulse frequency modulated signal that can be represented by a trigonometric series. Knowledge of the VCO-ADC output spectrum allows accurate evaluation of the SNDR dependence with the VCO oscillation frequency and gain constant. The SNDR predictions of the proposed model have been compared to behavioral simulations displaying only a deviation of 0.7 dBThis work was supported by the CICYT project under Grant TEC2010-16330.Publicad

Presilicon Circuit-Aware Linear Least Squares Spectral Analysis for Time-Based Data Converters

Presilicon time-based data converter spectral analysis usually incurs long simulation times. This brief shows an approach for the estimation of the data converter's spectral components and noise floor based on a small simulation window. Additionally, it provides two useful estimates of the technique's expected accuracy. The method is based on circuit-aware linear least squares spectral analysis. It can be applied together with the accuracy estimate and knowledge of the noise spectrum's shape during the design time of time-based data converters. It provides a significant advantage over classic fast Fourier transform-based techniques for time-based data converters. Both a theoretical background and simulation results are provided for a voltage-controlled oscillator (VCO)-based analog-to-digital (A/D) converter. The technique provides a good accuracy for both the spectral components and the data converter's noise floor. The accuracy estimate expresses the technique's performance, achieving a worst case error of only 5 dB, which proves its usability. © 2004-2012 IEEE.status: publishe