Sharif Digital Repository

In recent years, eLoran system has been introduced as backup to global navigation systems like GPS, because of their vulnerability. eLoran is a low frequency (100 kHz) system. Its long wavelength allows indoor positioning.
Main eLoran advantages rather than Loran-C are: better accuracy (near 10m), using 9th pulse positioning modulation (PPM) as loran data channel (LDC) and all-in-view receivers
In this thesis, eLoran pulses are simulated in GRI. Also, a new analoge-digital circuit for faster pulse detection is developed.
Also, it is proved that an oscillator with same frequency and phase as enterance signal, responses faster than a band pass filter and envelope detector. So, a... 

In this thesis, new boundary conduction mode boost PFCs are proposed and implemented for different power levels according to the characteristics and requirements of each power level. For medium power applications, we have proposed a new zero voltage switching PFC based on a synchronous boost converter which is controllable with conventional boundary conduction mode PFC control ICs without requiring any additional timing adjustment control circuits other than a special high side driver that consists of only low voltage components. Based on mathematical calculations, we have proposed two sipmle circuit solutions to reduce the high level of line current zero crossing distortion in the proposed... 

Long-term Multi-Channel Bio-Signal monitoring in a comfort way is demanding for emerging applications in everyday life. Typically, in multi-channel amplification, one amplifier per channel is employed. However, the bio-signal amplification requires lower bandwidth in comparison with the available speed of CMOS amplifiers. Therefore, it is sensible to develop a practical circuit trading the excess CMOS bandwidth with power consumption. The proposed circuit, which has three inputs, performs amplification through three stages; First, the inputs are applied to a 3 to 1 time-domain multiplexer. Second, a Current Feedback Instrumentation Amplifier (CFIA) is utilized. Finally, the amplified signal... 

LiFi is a bidirectional wireless optical networking technology that uses commercial LEDs for data transmission. In simpler terms, LiFi is considered a light-based WiFi that uses light instead of radio waves to transmit information. Using light to transmit data allows LiFi to deliver a couple of advantages, such as working in areas susceptible to electromagnetic, working across higher bandwidth while offering higher transmission speeds. Finally, the security of this technology is much more than other ways of communication since the light cannot penetrate through walls and doors, so other people who are not in the room could not access data.In this dissertation, a Li-Fi receiver that uses... 

Nowadays, optical networks is one of the best options for ultra high speed data transmission. An optical network is either implemented using optical fibers or via free space optical links. Fiber optics has gained special popularity among all mediums of data transmission, however, builing a fiber infrastructure is not a cost or time effective solution and this is the main limitation of these networks. Free space optics has been an attractive answer to overcome the drawbacks of the fiber optic networks. On the other hand, atmospheric turbulence and scattering are the main factors affecting FSO’s availability and Reliability. As a result, Design of next generation FSO networks need high speed... 

Deployment of demands, increase in users and new services highlight the necessity of effective frequency allocation i.e. dynamic allocation instead of fixed allocation. Cognitive radio is a proper solution for dynamic frequency allocation. Cognitive radio can scan the spectrum and use the idle bands for transmitting and receiving data. The main part of this radio which is responsible for the most pivotal task is spectrum sensing. Recently, varied methods have been proposed to sense the spectrum. The scope of this research is on designing a very high-speed spectrum sensing system. In this thesis, in order to meet the required scan rate, a tunable complex filter with 40MHz pass-band has... 

The use of electric vehicles is increasing day by day due to the reduction of pollution, reduction of fuel costs, higher efficiency, etc. Increasing the distance traveled in each charging period of the electric vehicle battery pack and increasing the lifetime of the battery cells are the most important challenges facing the electric vehicle industry. In electric vehicles, Li-Ion battery cells are used to store energy, so to improve these challenges, we first need to carefully examine the behavior of these cells with the various conditions that occur during operation to design other circuits such as balancing circuits, Battery management system, etc. In this thesis, first a model is proposed... 

The continous growth of wireless networks, the increasing numbers of users and devices, along with the demand for higher data rates have intensified the frequency band limitations as the communication medium. In search for more efficient methods to use this limited resource, the cognitive radio approach that allocates the local unused frequency bands to potential users has attracted considerable attension.
A fundamental and unseperable part of any cognitive radio system is its need to search, detect and understand the surrounding frequency spectrum. Although various methods have been already propose to overcome the challenges of this domain, simpler and more reliable methods are still in... 

According to increasingly utilization of different frequency spots, RF receivers are allways under the threats of compression and desensitization because of large out-of-band or in-band blockers. The IC technologies afford fast, low-resistance switches as scaling keeps going on. With this mind, the Linear Periodic Time Varying circuits, in which the switches play the most dominant role, will be a sensible candidate for the concerns of blocker detection and rejection. Furthermore, nowadays’ receivers should be reconfigureable so as to be tunable at different frequency bands and satisfy contrastive standards. In this regard, the LPTV filters provide vast range of tunablity not only with... 

Advanced Driver Assistance Systems (ADAS) and autonomous vehicles are expected to play a pivotal role in reducing road accidents and mitigating human error. LiDAR (Light Detection and Ranging), as a key enabling technology, significantly contributes to the realization of autonomous vehicles through its high accuracy and high speed. A fundamental requirement for the effective operation of LiDAR is optical beam steering, which enables precise three-dimensional imaging of the surrounding environment. Currently, conventional beam steering techniques primarily rely on mechanical components. Despite their widespread use, these approaches suffer from substantial limitations in terms of speed,... 

The aim of this research is to investigate the challenges of cardiac signal recording and to propose solutions for improving it. First, the function of the heart, the role of electrodes, and the process of generating an electrocardiogram (ECG) are explained. One of the most significant issues in ECG recording during patient movement is motion artifact, which makes interpreting the cardiac signal difficult. To study this problem, an experimental circuit was built, and approximately 60% correlation was observed between the electrode–tissue impedance (as an indicator of motion artifact) and the cardiac signal. In addition, a chip called TMCIA was characterized for the purpose of recording... 

Every year millions of people around the world die because of car accidents, most of which are caused by human faults. This has greatly increased the need for advanced driver-assistance systems (ADAS) and self-driving cars. Currently, driver assistance systems rely mainly on radar sensors and cameras to detect various objects and obstacles around the vehicle. Radar, due to its low lateral resolution, and Camera, due to its sensitivity to environmental conditions and lack of distance measurement, do not perform well alone. Therefore, we need light detection and ranging (LiDAR) that measures the distances from objects using laser light. Due to the micrometer wavelength of light, LiDAR can have... 

The issue of automation has always been a concern for humans over the years. Replacing humans with machines or intelligent software to perform various tasks can significantly improve the accuracy and speed of those activities. One of the long-standing aspirations of humanity has been the automation of driving. In addition to freeing individuals from the time-consuming task of driving, automating vehicles can also dramatically reduce road accidents. To achieve this goal, vehicles need to be equipped with various sensors such as radar, cameras, lidar, and more. Each of these sensors has its advantages and disadvantages, and as a result, all of them must be used for safe driving. In this... 

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... 

Wireless Power and Data Transfer (WPDT) is a major part of a biomedical implant system. Maximiazing the Power Transfer Efficiency (PTE) and maximizing the data rate are the main challenges in WPDT. In a conventional biomedical implant system, a single inductive link is used to transfer both power and data from outside the body to inside. Data is transmitted by modulating one of the carrier signal properties, i.e., amplitude, frequency or phase. While being simple and robust, this method suffers from the fundamental trade-off between the PTE and data rate. To address this issue, various methods have been proposed including multiple carriers and multiple inductive links, and inductive link... 

Due to extension of wireless networks, indoor positioning service becomes more important in new generations of WLAN networks. Complicated nature of indoor propagation channel decreases the quality of localization service in urban area. To overcome this problem, we surveyed characteristics of indoor radio channels and proposed methods to specify channel parameters to reduce its effect on positioning error. For this purpose, we introduce some super resolution methods and compare their precision and ability to implement on hardware. Among all of them, Matrix Pencil is selected and its mathematical functions are analyzed and stated in numerical algorithms and basic units. In implementain phase,... 

Efficient radio frequency (RF) power amplifiers (PAs) are critical in portable battery-operated wireless communication systems because they can dominate the power consumption. Linear amplifiers are enough linear but suffer from poor efficiency. On the other hand, switching power amplifier are efficient but are nonlinear and just amplify constant envelope signals. Two conventional methods for increasing transmitter efficiency and linearity are envelope elimination and restoration (EER) and envelope tracking (ET). In both methods, supply modulator controls RF power amplifier supply based on the signal envelope. Efficiency and bandwidth are critical factors in supply modulator. Thus hybrid... 

Various safety systems have been designed and developed in recent decades, but one of the most important issues is the improvement of safety of such systems and that is the goal of this research. In this thesis, while introducing different methods of designing an electronic system, we designed one of these safety systems: the Airbag system in accordance with ISO 26262 by considering standard requirements, prediction of potential hazards of the system, and its safe design at the system level. The designed system is capable of detecting the car crash in a precise and timely maner. The airbag will deploy within 45 milliseconds protecting the health and safety of occupants of the car and in... 

In this work, various aspects of the design, analysis, optimization, and calibration of wideband multi-path receivers have been investigated, with a focus on their application in fifth-generation (5G) mobile communication systems. In Chapters 1 to 3, the 5G wireless communication standard is first reviewed, and then the system-level parameters required for designing receivers compatible with this standard are extracted. Additionally, the architecture of wideband multi-path receivers is studied, and along with a mathematical modeling of such receivers, a technique for receiving the subharmonics of the clock signal is introduced. In Chapter 4, a current-mode receiver capable of receiving the...