- ELECTRONICS LETTERS Journal
- June 2018
Digital Object Identifier (DOI)
International Standard Serial Number (ISSN)
Electronic International Standard Serial Number (EISSN)
- The performance of open-loop ADCs implemented with VCOs is limited by VCO non-linearity and first-order noise shaping. The resolution limitation imposed by first-order noise shaping can be compensated by a ring oscillator VCO with many output phases. Linearity can also be improved by using a feedback loop around the VCO closed with a DAC. However, a long ring oscillator may require a DAC with a prohibitive number of bits if feedback is used to compensate distortion. This Letter proposes an ADC architecture based on the Leslie-Singh Sigma-Delta (Sigma Delta) modulator that allows to implement a distortion correction loop around a VCO with a simplified DAC of few levels, yet keeping a large number of output quantisation levels to maintain resolution. The Letter discusses the system-level architecture and shows an implementation circuit example to verify the effective correction of distortion.
- voltage-controlled oscillators; digital-analogue conversion; circuit feedback; distortion; compensation; sigma-delta modulation; quantisation (signal); vco-based adc; simplified dac; nonlinearity correction; open-loop adc performance; vco nonlinearity; first-order noise shaping; resolution limitation; ring oscillator vco; feedback loop; distortion compensation; leslie-singh sigma-delta modulator; leslie-singh sigma-delta modulator; distortion correction loop; quantisation levels; system-level architecture