Sharif Digital Repository

Nowadays, increasingly improvements in the digital technology and the advantages of using digital signal processing methods lead engineers to use digital signal processing instead of analog processing in variant domains. However, speed limitations in analog to digital converters (ADCs) and data transfer ports prevent its penetration to high frequency signals region. In this thesis, an Instantaneous Frequency Measurement (IFM) system that can measure frequency in the range of 2-18 GHz is implemented fully digital (DIFM) on FPGA. To do so, monobit sampling technique with the sampling rate of 10 GHz is selected, and GTX high speed serial port is configured to transfer digital data into FPGA.... 

High speed data converters are very often used in telecommunication systems. Since these systems are increasingly used in mobile form reducing the power consumption in these circuits is of great importance. The goal of this project was to design a pipeline 10 bit converter for a sample rate of 500 M sample/s with a power consumption of 50mW for the input level of 1Vp-p and a 1.5V power supply in 0.18μm CMOS technology. To reach these goals a number of low-power techniques are proposed in various levels of abstraction. In system level, the sampling and feedback capacitors, as well as the stage resolution of the ADC is optimized .And to... 

High speed data converter are very often used in telecommunication systems. Since these systems are increasingly used in mobile foem reducing the power consumption in these circuits is of great importance. The goal of this project was to design a pipeline 10 bit converter for a sample rate 200MS/s with a power consumption of 35 mW for the input level of 1Vp-p and a 1.8V power supply in 0.18um CMOS technology.
To reach these goals, a number of low power techniqes are proposed in various levels of abstraction. In system level, the sampling and feedback capacitors is optimized analytically which leads to simple back-envelope formulas to calculate the optimum values. In circuit level, a... 

SAR ADC is a data converter which is based on binary search to convert an analog signal to a digital signal. Unlike other converters like pipeline, most of its constituent parts are digital, and hence scalable with process and consume less power, moreover can have better speed and power performance. With advanced technologies, namely 45nm and 32 nm CMOS, SAR ADCs are preferable as they consume much less power and area, therefore well-suited for portable applications, as opposed to Flash and Pipleline converters.
The main drawback of this type of converter is its limited speed which is due to the fact that one clock cycle is required to evaluate each bit. As a result, there is a... 

Low power and high speed analog-to-digital converters (ADCs) are the key elements of communication and computing systems. There are several ADC structures such as delta-sigma, flash, pipeline, and successive approximation register (SAR) for different applications, albeit SAR ADCs are natural candidates of onchip designs for their low power and scalability benefits. Nowadays, SAR ADCs are widely being used in low-power moderate-resolution applications which need several tens of MS/s to low GS/s sampling rates. By virtue of the technology scaling power consumption of digital parts of a SAR ADC is reduced significantly. As a result, in a SAR ADC the power consumption of the digital-to-analog... 

ADC is one of the key functional blocks of any mixed signal system and therefore must be optimally designed concerning power, performance, resolution and silicon area. Among different architectures have been employed up to now, successive approximation register ADCs are known as the ones with lower power, more simplicity and lower sampling rate. Benefiting from scaling down the CMOS technology results in higher sampling rate and lower power SAR ADCs replacing other types of ADCs. To achieve the desired ADC performance, efforts are usually focused on the improvement of circuit techniques as well as on the introduction of new or combinational architectures based on SAR ADCs. This thesis aims... 

Effect of resolution of Time to Digital Converters (TDCs) on the performance of All-Digital Phase Locked Loops (ADPLLs) and capability of achieving higher resolution in advanced technologies lead to introducing different kinds of TDCs. Beside the analysis of different kinds of TDCs, This thesis proposes three new TDCs based on the time amplifi-cation concept. A new pipeline TDC is designed using a wide dynamic range time amplifi-er. A new method is used to widen dynamic range of the conventional time amplifiers. In order to get a low power high resolution conversion, a new delay element design is devel-oped to reduce the delay value and its sensitivity to mismatch and process variations.... 

Delta-Sigma Analog-to-Digital converters have been positioned themselves as robust reliable converters so far. The magic Of extracting high resolutions from low bit ADC has made them popular between designers. Previously, the noise-shaping magic was used in high-resolution applications such as high-quality audio signal converters. However, as the technology scales and proceeds, these converters are approaching RF applications, too. Power and OSR trade-off limits this progress. To increase OSR in bandpass delta-sigma modulators, more power should be consumed to increase the quality factor of loop filters. In this thesis, a systematic approach has been utilized. An n-path filter is employed... 

The digital nature of Successive Approximation Register (SAR) Analog to Digital Converter (ADC) suits them for the new technologies with small gate length and low power applications. Applications such as ultra-wideband receivers, satellite receivers and high speed serial links demand medium resolution and high sampling rate ADCs. Due to binary search algorithm speed limitations, SAR ADCs belong to low to moderate speed category. In this thesis time-interleaving and two-bit-per-cycle technique are used in order to increase SAR ADC sampling rate. These techniques are both sensitive to offset and if the comparators used in SAR ADC have different offsets signal-to-noise-and-distortion will be... 

In this research, we propose analog to digital (A/D) converters based on Level Crossing (LC) sampling and the corresponding signal processing techniques for effecient acquisition of spectrum-sparse signals. Spectrum-sparse signals arise in many applications such as cognitive radio networks, frequency hopping communications, radar/sonar imaging systems, musical audio signals and many more. In such cases, the signal components maybe sparsely spread over a wide spectrum and need to be acquired at a reasonable cost without prior knowledge of their frequencies. Compared with the literature, the proposed scheme not only enables efficient acquisition of spectrum-sparse signals with a less complex... 

In many industries, including oil and gas industries, power plants, refineries, petrochemicals, steel and cement industries, industrial complexes and consumer industries, there are tanks for storing materials. It is necessary to measure level of products while they are stored in tanks of different sizes. Ultrasonic is one of the non-contact and accurate measurement technologies that can provide a suitable solution for liquid tank monitoring. The purpose of this thesis is to design and build the electronic parts (transmitter and receiver circuits) of an ultrasonic system that is capable of detecting levels at a distance of less than 5 meters with an accuracy of 0.5 % full scale. In this... 

A major breakthorugh in all-optical wireless and wired communication networks is taking place in the last mile such as access networks. In this case، study-ing various multiple-access techniques in all-optical domain، especially optical code-division multiple-access (OCDMA) technique is of utmost importance. In this thesis we study several key signalings and modulation techniques in the con-text of their performance، energy and throughput efficiency for OCDMA systems. In particular we introduce novel multilevel signaling techniques for OOC-based fiber-optic CDMA systems and present their corresponding all-optical receiver structures using advanced optical devices such as optical-logic-gate...