Modeling Asynchronous Sigma-Delta Modulators.
Abstract: This thesis
studies asynchronous sigma-delta modulators (ASDM) which are the core part of
asynchronous sigma-delta converters (ASDC). The asynchronous sampling techniques provide
a low power, clock-less data acquisition approach with a less sophisticated design
constrains offering significant power savings while keeping increasing speed in scaled
deep submicron technologies. Our con... read moretribution in this thesis is briefly listed as below:
1) thoroughly analyzed the different error sources in a bi-level ASDM 2) compared
multi-level ASDM with bi-level ASDM 3) introduced the band-pass ASDM and analyzed it
Commonly, ASDCs consist of two main parts: 1) a duty-cycle modulator (DCM) which
transforms amplitude information of the input signal to the time information 2) a
time-to-digital converter (TDC) following the DCM unit which quantizes and digitizes the
time information. Mainly focusing on the DCM part of ASDCs, in the first part of this
thesis, after discussing the architecture of ASDMs, it has been shown that they are an
acceptable realization of DCMs. In following, we evaluate different types of errors
affecting performance of such systems. We have shown that how fixed and dynamic errors
affect the performance of the ASDM. The second part of the thesis is focused on
alternative architectures of ASDMs. A multi-level asynchronous sigma-delta modulator
(ML-ASDM) generates a multi-level square wave signal whose duty-cycle is modulated by
input signal. The resulting signal can be then quantized by any following TDC block. We
have proved that in a ML-ASDM converting input amplitude information to multi-level
duty-cycle modulated square waves not only doesn't help improving the performance of the
modulator but also it introduces non-harmonic distortion in the band of interest which
drastically degrades the performance of the modulator, compared with bi-level ASDM.
Another different ASDM structure discussed in this report is a band-pass asynchronous
sigma-delta modulator (BP-ASDM). This type of ASDM, for the first time, is introduced in
this thesis. It is targeted to be implemented in narrow-band radio-frequency
applications. In case of implementing a high resolution TDC, we have shown that this
type of modulator helps converting high-frequency signals to digital
Thesis (M.S.)--Tufts University, 2013.
Submitted to the Dept. of Electrical Engineering.
Advisor: Sameer Sonkusale.
Committee: Brian Tracey, and Anil Saigal.
Keyword: Electrical engineering.read less