Time-domain data conversion has recently drawn increased research attention for its highly digital nature in favor of process technology scaling. Also, as the time information being carried by binary voltage, time-domain operation is much less sensitive to voltage noise compared to conventional voltage domain operation. However, for analog-to-digital converter (ADC)...
Nowadays, needs for wideband and high accuracy analog-to-digital converter are increasing rapidly in manifold applications such as wireless communication, digital video and other consumer electronics. Besides, low power consumption is required to have longer battery life in portable systems. CMOS technology scaling and innovative modulator topology make the implementation much...
Continues-Time (CT) Delta-Sigma (ΔΣ) Analog-to-Digital Converters (ADCs) have one important constrain, namely the excess loop delay. Most previous excess lop delay compensation methods need to know the exact value of the excess loop delay in advance. However, the value of the excess loop delay is a uniformly distribution random variable....
VCO-based ADCs have recently emerged as attractive alternative to conventional DeltaSigma (ΔΣ) modulator architectures. Few salient features of a VCObased ADC are: 1) the quantization noise is 1st order noise shaped, 2) it is an open loop architecture, and, 3) its implementation is mostly digital in nature. Hence, they are...
Sensors find a variety of applications in portable electronics, automotive and biomedical solutions. The demand for low power and high dynamic range makes the design of digital sensor readout circuits quite challenging. Traditionally, these circuits are realized using amplifiers with passive feedback or precision analog comparators which are power hungry...
The resolution of analog-to-digital converters can be distinguished as absolute resolution, or average resolution. This study reviews average resolution enhancement techniques and proposes a method which is particularly applicable as a low-cost modification to a high-speed waveform acquisition system. This method uses oversampling combined with computationally simple digital filtering to...
Modern day CMOS processes are characterized by voltage scaling and geometry scaling. Geometry scaling helps reduce gate delays, thereby aiding in the design of data converters which use time based processing. Another artifact of geometry scaling is the increase in complexity of digital circuitry available on traditional analog ICs, as...
In this dissertation, time-based signal processing techniques and their applications in oversampling and noise-shaping data converters are examined. These techniques demonstrate the ability to shift the burden of high performance analog circuits from the compressed voltage-domain to the augmented time-domain. First, the potential of high order noise-shaping and phase-domain feedback...
As advanced wired and wireless communication systems attempt to achieve higher performance, the demand for high resolution and wide signal bandwidth in their associated ADCs is strongly increased. Recently, time-domain quantization has drawn attention from its scalability in deep submicron CMOS processes. Furthermore, there are several interesting aspects of time-domain...
Voltage controlled oscillator (VCO) based ADC is an important class of time-domain ADC that has gained widespread acceptance due to their several desirable properties. VCO-based ADCs behave like an open-loop continuous time ΔΣ modulator and achieve excellent resolution by first order noise shaping the quantization error. However, the SNDR of...
This thesis describes the development of a flash analog-to-digital converter based on
current-mode technique. The advantages of current -mode technique are higher speed,
smaller chip area, and simple division of reference current based on current mirror. A
current-mode comparator is designed consisting of a cascode current mirror and a
current...
Delta-Sigma Modulator-based Analog-to-Digital converter design is an active area of research. New topologies require extensive simulations to verify their performance. A series of improvements were made to an existing circuit simulation package in order to speed the simulation process for the designer. Various examples of these improvements are presented in...
Oversampling analog-to-digital and digital-to-analog converters are gaining more
popularity in many signal processing applications. Delta-sigma modulators are used in practical applications of oversampling systems because of their apparent practical advantage over other oversampling converters in terms of insensitivity to the inevitable imperfection of the analog circuitry.
In Δ∑ modulators, analog...
This thesis presents the design of a 10 bit Analog to
Digital Converter which consists of a 6 bit flash followed
by a 4 bit pipeline architecture. The total system is
described and the 4 bit pipeline is implemented on a bipolar
process.
The objective of this research is to...
In an industrial and consumer electronic marketplace that is increasingly demanding greater real-world interactivity in portable and distributed devices, analog to digital converter efficiency and performance is being carefully examined. The successive approximation (SAR) analog to digital converter (ADC) architecture has become popular for its high efficiency at mid-speed and...
Oversampled delta-sigma modulation is one of the widely used A/D conversion
techniques for narrow bandwidth signals. In this study several new lowpass and
bandpass delta-sigma modulator architectures as well as novel pseudo-N-path integrators
that can be used in implementing these architectures are proposed.
By using multiplexing techniques the new lowpass...
Multi-level decision feedback equalization (MDFE) is an effective sampled signal processing technique to remove inter-symbol interference (ISI) from disk read-back signals. Parallelism which doubles the symbol rate can be realized by utilizing the characteristic of channel response and decision feedback equalization algorithm.
A mixed-signal IC implementation has been chosen for...
Multi-level decision feedback equalization (MDFE) is a sampled signal processing technique for data recovery from magnetic recording channels which use the 2/3(1,7) run length limited code. The key adaptive feedback loops in MDFE are those which perform the timing recovery, gain recovery, dc offset detection, and adaptive equalization of the...
Delta-sigma modulators are currently a very popular technique for making high-resolution
analog-to-digital and digital-to-analog converters (ADCs and DACs). Most
delta-sigma modulators in production today employ single-bit quantization because a 1-bit DAC is inherently linear, whereas a multi-bit DAC is not. Were it not for this drawback,
the use of multi-bit...
The advance of digital IC technology has been very fast, as shown by rapid development of DSP, digital communication and digital VLSI. Within electronic signal processing, analog-to-digital conversion is a key function, which converts the analog signal into digital form for further processing. Recently, low-voltage and low-power have become also...
This thesis describes compensation techniques for cascaded delta-sigma A/D
converters (ADCs) and high-performance switched-capacitor (SC) circuits. Various
correlated-double-sampling (CDS) techniques are presented to reduce the effects of the
nonidealities, such as clock feedthrough, charge injection, opamp input-referred noise and
offset, and finite opamp gain, in SC circuits. A CDS technique...
The precise measurement of a capacitance difference or ratio in a digital form is
very important for capacitive sensors, for CMOS process characterization as well as for the
realization of precise switched-capacitor data converters, amplifiers and other circuits
utilizing ratioed capacitors. This thesis introduces design techniques for on-chip capacitor
ratio...
Continuous process scale-down and emerging markets for low-power/low-voltage mobile systems call for low-voltage analog integrated circuits. Switched-capacitor (SC) circuits are the building blocks for analog signal processing and will encounter severe overdrive problems when operating at low voltage conditions. There exist three techniques to solve the problem, but with their...
The design of a switched capacitor successive approximation A/D converter is discussed in this thesis. This design adopts a novel capacitance mismatch error cancellation algorithm proposed in references [25, 27]. Detailed charge domain analysis is given in this thesis, which results in an improvement of the proposed algorithm by tracing...
A radix-based calibration technique was previously proposed with a two-stage algorithmic analog-to-digital converter (ADC). The objective of this work is to verify the capability of radix-based calibration for a true multi-stage ADC. In order to prove the idea, a single bit-per-stage, 20-stage pipelined ADC is designed in a 0.35-μm CMOS...
A differential current-mode track-and-hold (T/H) amplifier is used to sample an analog input signal. A new closed-loop current-mode architecture has been developed that overcomes the stability problems associated with closed-loop architectures. The T/H circuit has been fabricated in a 0.35-μm quad-metal, double-poly CMOS process. The measured total harmonic distortion (THD)...
Utilizing a two-capacitor topology, the digital implementation of an audio-band successive-approximation analog-to-digital converter (ADC) is explored in the context of mismatch-shaping where the mismatch estimates are accurate to the first order. A second-order Δ∑ loop was found to be effective in system simulations given a 0.1% capacitor mismatch. Spectral analysis...
This thesis proposes a novel fully digital technique for the estimation and correction of the DAC error in multi-bit delta sigma ADCs. The structure of the DAC error is indicated through a simple model for unit-element based DACs. The impact of the DAC error on the performance of ADC is...
Delta-sigma analog-to-digital converters traditionally have been used for low speed, high resolution applications such as measurements, sensors, voice and audio systems. Through continued device scaling in CMOS technology and architectural and circuit level design innovations, they have even become popular for wideband, high dynamic range applications such as wired and...
There is a significant need in recent mobile communication and wireless broadband
systems for high-performance analog-to-digital converters (ADCs) that have wide
bandwidth (BW>5-MHz) and high data rate (>100-Mbps). A delta-sigma ADC is
recognized as a power-efficient ADC architecture when high resolution (>12-b) is
required. This is due to several advantages...
Two aspects of ADC system performance are addressed in this work. First, the combination of the ADC and its associated reference are co-designed for an energy constrained remote sensing system. Second, sampling linearity is mathematically analyzed as a function of frequency to provide enhanced understanding into an ADC's requisite sampling...
As CMOS processes keep scaling down devices, the maximum operating frequencies of CMOS devices increase, and hence circuits can process very wide band signals. Moreover, the small physical dimensions of transistors allow the placing of many more blocks into a single chip, including highly accurate analog blocks and complicated digital...
Delta-sigma analog-to-digital converters (ADCs) are suitable for many applications due to several advantages such as relaxed anti-aliasing filter, high signal-to noise and distortion ratio (SNDR) and most important of all, reduced sensitivity to
analog imperfections.This thesis introduces several structures to overcome loop imperfections and stability issues in delta-sigma modulators. First,...
Advances in process technologies have led to the development of low-power high speed digital signal processing blocks that occupy small areas. These advances are critical in the development of portable electronic devices with small feature size and long battery life. However, the design of analog and mixed-signal
building blocks, especially...
High speed and high resolution analog-to-digital converter is a key building block for broadband wireless communications, high definition video applications, medical images and so on. By leveraging the down scaling of the latest CMOS technology and the noise shaping properties, delta-sigma (ΔΣ) ADCs are able to achieve wide-band operation and...
The objective of this work is to explore the feasibility of replacing conventional op-amps with inverters in switched-capacitor (SC) circuits. In order to verify the idea, a low-pass filter (LPF) and a second-order delta-sigma (∆Σ) analog-todigital converter (ADC) are designed in the 0.5-m CMOS technology. The low-pass filter structure is...
Pipeline analog-to-digital converters (ADCs) have long been used in high-speed systems for power-efficient data conversion. Broadband communication and video processing systems are placing high demands on converter accuracy and speed (above 14 bits and in the multiple-MHz range). The increasing converter requirements coupled with lower supply voltages in modern processes...
This thesis proposes a novel technique for the design of pipelined and cyclic ADCs utilizing generalized radix gain stages. Several models have been proposed for the optimization of high performance pipelined ADCs by various researchers. This work builds upon them, using a simple but accurate model to estimate the optimal...
Multi-Gigahertz sampling rate Analog-to-Digital Converters (ADC) with 5-8 bits resolution are used in many signal communication applications. Unfortunately, the performance of the high speed ADC is limited by the timing accuracy of the sampling clock. A small sampling uncertainty can cause a large error in the sampled voltage and result...
A new approach to oversampled delta-sigma A/D converters ( AZ modulators ) is introduced, where a differential pseudo-Npath filter stage is used as a basic cell. In this band-pass application, the z to -zN transformation is employed to realize a RAM-type pseudo-2-path lossless integrator. The bandpass second-order and 4th-order delta-sigma...