Multi-level asynchronous delta-sigma modulation based ADC

A Multi-level asynchronous delta sigma modulator consist of several Schmitt-triggers and a novel time-to-digital converter is presented as a core of a delta sigma modulation based analog to digital converter (ADC). The modulator firstly modulates the amplitude of its analog input signal to a multilevel asynchronous duty-cycle modulated signal. Then a time to digital converter (TDC) must be applied to generate digital representation of the received signal from the multi-level asynchronous duty-cycle modulated signal. A multi-level structure has been developed in this work while the prior works often used a single Schmitt. One of the most important limitations in conventional asynchronous delta sigma modulation based ADCs is the resolution of time-to-digital converter and it depends on CMOS technology. To adopt for multi level modulator, here, a novel TDC is presented. Simulation results show that using the proposed multi-level delta sigma modulation based ADC allows achieving better performance comparing to conventional single-level modulators.