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... 

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... 

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... 

Ultra-wideband (UWB) receivers have long been utilizied as a low-power solution for many applications, namely positioning, sensor network, and radar systems. As their name suggests, owing to the ultra-wide bandwidth nature of these receivers, which cover frequencies from 3.1GHz all the way to 10GHz, they entail many challenges at all levels of abstraction. Two of these most important challenges are in-band interferers, e.g., IEEE802.11a, and jitter. Because of the low-power operation of UWB receivers, with PSD of <-41.3dBm/Hz, the majority of the UWB RX’s function is based on the correlation principle, making it vulnerable to jitter. In recenet years, a new attention has been paid toward the... 

With the ever-increasing communication need for propagating signals in authorized empty bands, the goal of this thesis is based on finding these unused bands and using them,which called Cognitive Radio. In this project, design and implementation of radio frequency building blocks of a receiver in the UHF band (400 to 800 MHz) is performed. In this project, however, the radio frequency building blocks include low noise amplifier, high-frequency quadrature mixers, high-frequency oscillators, tunable low-pass filter,band select filter,phase-locked loop and synthesizer, all of which are introduced, examined and implemented. Moreover, a new method which mitigates the speed limitation is verified.... 

Ultra-wideband (UWB) frequencies with low level of power spectral density, which is set by FCC standard, have long been utilized in many short range applications, namely sensor networks, indoor positioning and radar systems. As their name suggests, the ultra-wide bandwidth of this standard, covering frequencies from 3.1 to 10.6GHz, provides high data rate communications. Two of the most critical challenges toward UWB receiver design is narrow-band interference coexistence, including IEEE802.11a and jitter due to the very narrow width of the UWB pulse in time domain. General previously proposed solutions to receive these narrow pulses is based on correlation principle, which is very sensitive... 

One of the serious challenges in Ultra-Wideband (UWB) systems, especially Impulse radio (IR) systems, is the IEEE 802.11a in the middle of the UWB band (In band Interferer) which affects the system performance severely. Matched filter concept shapes the output noise based on its spectrum. For solving the mutual interference between UWB and narrow-band (NB) systems, the unique properties of modified Hermite pulses is utilized to develop a pulse for UWB communications. Matched filter is implemented by designing this pulse featuring notches that can be tuned to a certain frequency. Therefore, NB interferer can be nulled out passing through the matched filter. 0.18 µm CMOS technology has been...