Sharif Digital Repository

Numerical Simulation of two-dimensional steady compressible fluid flow on unstructured grids was accomplished using a fast implicit algorithm. To solve the copmlete two-dimensional Navier-Stokes equations, implicit time stepping was used which results in a large sparse linear system in each iteration. To solve the linear system, the biconjugate gradient method which belongs to Krylov subspace methods family, with an ILU(0) preconditioner was used. For accelerating the solution in large problems, parallel processing was used for linear system to be solved faster. Two upwind methods, namely Roe’s and AUSM+ methods were used for spatial descritizaion of inviscid fluxes with a MUSCL algorithm... 

Nowadays, swift development of cellular network with the increased penetration rate, have made mobile voice channels widely available almost everywhere with higher priority comparing to the other conventional channels, e.g., GPRS, EDGE, HSDPA and etc. Leveraging on this fact two important utilization can be considered. The first one is related to urgent transmitting of vital data. As mentioned earlier, since this channel deems to be available everywhere and, recalling its priority, it is even accessible in congestion condition, it can be exploited as an efficient way to transmit small volume of emergence data urgently. Transforming the crash data on the road is an example of utilizing such... 

Passive wideband reconnaissance receivers, listen to the radio and radar signals in the environment and estimate their important parameters such as direction of arrival (DOA). The wideband attribute for these receivers is to refer to their ability to receive wideband signals.Due to the use of processing gain, LPI radars reduce their transmitted signal power to see and not to be seen. On the other hand reconnaissance receivers can not have much processing gain, because they do not know the nature of the transmitted signal; Therefore, to increase the operational range of these systems, it is necessary to increase the signal to noise power ratio (SNR). This thesis examines the use of antenna... 

Target localization using positioning systems has long been considered by researchers in various fields.One of the important issues in localizing a target is the accuracy of its determined position. There are several parameters in the accuracy of position estimation. In a comprehensive view, these parameters can be divided into three general factors,including the relative geometry of the transmitters/receivers with respect to the target, the accuracy of measurements, and the type of target position estimator.The first factor, i.e. the relative geometry between the target and the transmit/receive antennas, plays an important role in localization accuracy. In the first part of this thesis, the... 

Nowadays, humans can travel long distances using land, air, and sea vehicles, moving from a certain origin to a desired destination. To navigate optimally and accurately, appropriate positioning methods need to be employed, which require accurate measurements of speed, acceleration, and movement angles throughout the journey. In everyday applications, nearly all inhabitants of the Earth utilize satellite positioning methods, which are easy to use and provide adequate accuracy. However, in specific scenarios for exploratory and military applications, the use of satellite localization is not feasible. The underwater scenario is one such case, where specific measurements must be taken using... 

This study presents a non-contact heart rate monitoring system using a rotating radar system. Vital signals from individuals are detected through radar, influenced by a distance and the antenna gain-proportionality factor. In the proposed method, the number of individuals within the radar range is first estimated based on Power Spectral Density (PSD) analysis. Using Independent Component Analysis (ICA), individual signals are extracted from the mixture composed of the linear combination of signals affected by the Doppler shift. The method uses a Constant False Alarm Rate (CFAR) threshold on the PSD, enabling simultaneous heart rate monitoring for multiple persons. Additionally, a... 

In-fiber and all-optical wavelength-selective signal processing are key aspects of fiber Bragg grating (FBG)-based devices in optical communication systems. FBGs with sharp filtering properties have already been used in fiber optic communication networks as dispersion compensators, optical add–drop multiplexers, fiber lasers, and optical label switching modules. We have developed an in-fiber wavelength-selective optical intensity modulator to superimpose low rate overhead data on the transit high-speed payload signals. The tunable fiber Bragg grating (FBG), as the heart of a wavelength-selective modulator (WSM), is designed and properly biased to implement the desired modulation... 

In this thesis, Particle Filter Methods are investigated in the context of moving targets tracking and the associated performance analysis. The application scope of this algorithm which is a particular case of Sequential Monte Carlo Method is far broader than tracking of moving targets. This algorithm can be used for mathematical calculations such as estimation of mathematical expectations, integrals, surface area of curves and many other mathematical calculations. In addition, it has applications in other branches of science like genetics. This algorithm is based on random sampling of a probability density function and resampling from the extracted samples. We change this algorithm in... 

Target localization in multiple-input multiple-output (MIMO) radar systems has been an active research topic during the recent years. Generally speaking, MIMO radars can be classified, based on the antennas geometry, into colocated and distributed architectures.The former provides waveform diversity and the latter makes use of spatial diversity provided by widely separated configuration of antennas, both of which improve localization and detection performance. In this study, we focus on the latter case. In this thesis, we investigate the localization problem in two parts, i.e., positioning based on bistatic time delay measurements and hybrid localization using combination of time delay,... 

This work is mostly about the analysis of direct position determination (DPD) approach as an emerging approach in source localization. Different aspects of this localization has been considered and some improvement techniques has been addressed. DPD is known as a replacement for the conventional 2-step localization approach in which the location of the target is estimated via the estimation of some interface parameters such as time of arrival, angle of arrival and etc. The main focus of this thesis is on the sensor placement problem in DPD in order to find an optimal configuration for the sensors to achieve the best accuracy in the estimation process. In this regard, the formulas of the... 

In general, multi-target tracking consists of estimation of the posterior density function of present targets at each scan in the observation area. These targets may have unknown and time varying number of targets. It is a tough job due to misdetections, false alarms, data association ambiguity, and nonlinear equations-non Gaussian noises. These all make it difficult to apply Kalman filter and its extensions such as extended Kalman filter and unscented Kalman filter. Monte Carlo methods, particularly particle filters, have recently aroused the interest of designers and enjoyed a lot of success to deal with multi-target tracking difficulties. In addition, they can handle nonthresholded data... 

Nowadays, with the increased penetration of wireless mobile networks (e.g. GSM, 3G, etc.), voice channels are widely available ubiquitously. This availability and wide coverage encourages utilization of such channels as a valuable available infrastructure for point to point secure data communication. This can be done either by using steganography and hiding the secure message in the voice passing through the channel or by ciphering and transmitting it through the voice channel as a speech-like signal. The proposed method for data communication or steganography through voice channels should be robust against lossy compression techniques applied by the vocoder block present in such channels.... 

Passive source localization accounts for the identification of the position and velocity of an object that emits electromagnetic/sound waves. This concept suggests various civil and military applications such as localization of the cellular phone users for emergency services, navigation, localizing radar and sonar sources. Received Signal Strength (RSS), Time of Arrival (TOA), Time Difference of Arrival (TDOA) and Frequency Difference of Arrival (FDOA) of the emitted signals are commonly used for position finding. Among all these measurement methods, localization using TDOA and FDOA is highly accurate and needless of any time synchronization between the source and the sensors. Common methods... 

Space-time adaptive processing (STAP) is one of the powerful algorithms for clutter suppression in airborne radars. In this algorithm, we need to estimate the covariance matrix of the range bin under test, exploiting adjacent range bins. Thus it is important for clutter to have the same space-time characteristics in different range bins; otherwise degradation will occur in clutter suppression. Therefore, traditional STAP is desired to be discussed in the side-looking mode in which clutters are range independent. In some situations, we need to employ STAP in the non-side-looking geometries of the arrays. For instance, sometimes it is needed to rotate the array to gain better coverage of... 

With the advent of new global navigation satellite systems and the technical progress of GPS, some valuable advantages can be achieved by using a combination of data from different constellations. There are some inter system biases between two separate constellation. One has to consider these biases in order to earn better accuracy in a multi constellation receiver. One of the main sources of the error in the position estimation is the random delay of the signal in the ionosphere layer. Recently GPS has released its dual frequency feature on civilian users. Using this feature, receiver will be able to estimate ionospheric delay due to its frequency dependence. The non-line-of-sight path of... 

Research on target localization in multiple-input multiple-output (MIMO) radars, has seen significant growth in recent years. In general, localization methods in these radars can be classified as direct and indirect methods. In the former, the cinematic specifications of target is directly extracted from the received signals, whereas in the indirect methods, different measurements are calculated from the received signals and then, the target position is estimated using the acquired measurements. In this thesis, by concentrating on indirect target localization methods and by taking practical problems, such as uncertainties in sensors position and velocity, asynchronous sensor clocks and... 

Passive Location is to obtain the location and velocity of a radio source using a source-generated signal in the environment and extract its parameters, which today have many applications in controlling security activities, tracking people and vehicles, emergency services, radar, Sonar, electronic warfare, and etc. . The location of a source is obtained by using a variety of methods such as received signal strength (RSS), signal angle of arrival (AOA), signal time of arrival (TOA), time difference of arrival (TDOA), and frequency difference of arrival (FDOA) of received signals. Many studies have been done in measuring and extracting data and solving the equations. However, little research... 

This thesis studies the problem of finding direction of arrival reecieved signals. One of the methods of direction finding is Time Modulated Array (TMA). Recently, a lot of research has been carried on using TMA for direction finding. Indeed, ease of implementation and resistance to noise has made this method interesting for researchers. The major drawback of these methods is that the baseline of array antenna needs not to be bigger than half of the wavelength of the maximum frequency and if this criterion is not met, the results will be multiple ambiguous solutions. However, sometimes, it is needed to have a bigger baseline (for instance, the case in which diameter of the antennas is bigger...