Sharif Digital Repository

Accurate modeling of clutter and detection of low observable targets within clutter are the major problems in radar signal processing applications. Recently, fractal geometry is applied to the analysis of high range resolution radar sea clutters. The intrinsic difference in the fractal dimension between sea clutter and the echoes from targets is extracted and used to detect targets. The box-counting method is widely used to estimate fractal dimension but it has some drawbacks never or rarely considered in literature. We explain the drawbacks and propose a new fractal dimension based detector to increase detection performance in comparison with traditional detectors. Both statistically... 

The synthetic aperture radar (SAR) is a microwave imaging radar that achieves high resolution while taking advantage of pulse compression technology and the Doppler effect. In typical radar systems, in order to obtain a good azimuth resolution, one should use an antenna with big aperture. However this is not possible in many cases. SAR has overcome this problem by moving the antenna and so making a synthetic aperture. In inverse SAR (ISAR) the radar antenna is static and synthetic aperture is created by the movement of target. Typical SAR imaging aims at the static targets and when the target is moving, it does not operate well. When detecting moving targets by SAR, both radar and target are... 

Hough transform is frequently used in radar applications. The structure of using this transformation in radars is so that it has been used only in Range radars which transmit short pulses and their primary goal is to make better estimation of the range of the targets. In this work, we introduce the ways in which we can use the Hough transform in Doppler radars which transmit long pulses and their primary goal is to make better estimation of target doppler. We must use Hough transform in time-doppler domain for this class of radars including continuous-wave radars. To prepare this time-doppler domain image some time-frequency transform must be applied to the radar received signal and a part... 

In this research, a new approach for TWS (Track While Scan) systems is introduced. Conventional TWS systems usually use target’s position (in Cartesian or polar coordinate systems), its velocity, and sometimes its acceleration (in main directions of coordinate system which is being used) as the elements of target’s state vector but the suggested algorithms use target’s velocity, course of motion and their rates of change as main tracking quantities and target’s position will be calculated after updating its velocity and course of motion. Hough transform is used as a powerful tool in detecting patterns which are identified with finite parameters (like lines, circles, ellipses, etc) to... 

The usage of the Hough transform, which has been proposed to detect straight lines in digital images, is studied as a target detector in search radars and its performance is compared with the conventional detectors. Then, a new method based on the Hough transform is introduced for detecting targets in a 3-D r-φ-t data space. The effectiveness of the new 3-D Hough detector is demonstrated through deriving the detection statistics analytically and comparing the results with those of several comprehensive simulations. The proposed detector is also evaluated with real radar data and its efficiency is confirmed. Then, the Average and Generalized Likelihood Ratio detectors are derived as the... 

In the recent decades, the estimation of direction of arrival has been an active area and some high resolution direction finding methods like MUSIC and ESPIRIT have been developed. These methods suffer from factors like mutual coupling. Direction of arrival estimation in presence of mutual coupling is a widely studied problem. In order to resolve this problem, many array calibration algorithms have been developed. However it may be impossible or difficult to set some calibration source in some situation. In this work we show that the effect of mutual coupling can be dynamically compensated by the inherent mechanism. First we show that how mutual coupling can degrades the performance of... 

The use of multiple-input multiple-output (MIMO) radar to overcome traditional radar weaknesses has received much attention in recent studies.For example, the detection of targets with low radar cross section (RCS) level is still very difficult since the target can be seen only from one side. MIMO radars by diversity of locations or waveforms solve this problem. One of the fundamental problems in the design of MIMO radars is optimal detectors.This problem has been investigated in recent years under various assumptions. We studied this subject under some assumptions such as single point target, Swerling scattering models for radar cross section and Gaussian interference.In this paper we... 

Military radars are mainly deployed to detect and track targets. They must be capable of working in dense environments where noise and clutter are also very likely present. Radars benefiting from random signals and especially noise radars can fulfill this goal. The transmitted signal in noise radar is a (modulated or unmodulated) noise signal; and it is what makes its performance superior to the conventional CW, FM and FM/CW radars, namely unambiguous range and Doppler measurement, robustness to noise, Low Probability of Detection and Interception (LPD and LPI), high Electro Magnetic Compatibility (EMC), inherent ECCM and CESM nature and thumbtack ambiguity function. In this thesis,... 

MIMO (Multi Input Multi Output) Radars issue is a new topic in Radar systems field and power allocation in these systems is very important to improve their performance.In this thesis, at first, two optimum detectors for MIMO radars with widely separated antennas are designed. In the first one, received signal in all receivers is gathered in a central processor and centralized detection is performed. This type of detection needs too much process power and is complex. Because of complexity of detector, probability of detection is very difficult to derive and deflection criterion is used for evaluating system performance. In the second one, each receiver processes received signals from all... 

Today, the use of radar technology and its various applications in different areas of science is no secret. The developed countries are looking to increase their ability to use new radar tools. Synthetic aperture radar is one of the most modern and efficient equipment imaging of the surface. One of the major advantages of synthetic aperture radar is imaging capabilities at night and bad weather conditions if the imaging methods used in the camera have limitations in night and bad weather conditions. There are different methods for extracting the images, one of the most important algorithms is Range Doppler Algorithm which is used to obtaining images from raw data received. Because of the... 

Environmental review, surveying land resources and the military mission requires high resolution imaging of large areas. in many cases, imaging should be performed during the night or in poor weather. Synthetic Aperture Radars (SAR)using long range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution image. The radar complements photographic and optical imaging capabilities because of them does not the time constraints, work and the weather. one of the most important methods for the extraction of synthetic aperture radar images by the method of imaging is the SPECAN algorithm. an important... 

In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has... 

Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features... 

Modern communication and space systems such as satellite communication devices, radars, SAR and radio astronomy interferometers are realized with large antenna arrays since this kind of radiating systems are able to generate radiation patterns with high directivity and resolution. In such a framework, conventional arrays with uniform inter-element spacing could be not satisfactory in terms of costs and dimensions. An interesting alternative is to reduce the array elements obtaining the so called ‘ thinned arrays’. Large thinned arrays have been exploited because of their advantages in terms of weight,consumption, hardware complexity, and cost over the... 

In MTI radars, digital filters utilizing non-uniform sampling are used to remove the echo of stationary targets or the ones with minor Doppler shift. These targets usually are associated with significant reflection causing small, high-speed targets not to be detected. In this type of filters, the use of non-uniform sampling prevents the blind speed issue and causes the first blind speed to occur at higher frequencies. The performance of such filters is characterized by two criteria: Coefficients and periods. Therefore, coefficient optimization in filter design has a dominant role in maximizing clutter rejection. Also, period optimization is used to prevent generating deep nulls in the... 

Today, SAR radars are one of the most practical tools for controlling and monitoring surface targets, and so far, several methods have been proposed to create a profile image of the reflection coefficient of surface targets in these Radars. The main problem in these methods is the ability to simultaneously create a reflection coefficient profile image for stationary and moving targets. To create a profile image of the reflection coefficient of moving targets, first it is necessary to detect and estimate its kinetic parameters.This thesis presents a method for detecting and estimating Ground moving targets parameters using Keystone transfer conversion and also presents a method for creating... 

By generalizing dictionary learning (DL) algorithms to Multidimensional (MD) mode and using them in applications where signals are inherently multidimensional, such as in three-dimensional (3D) Inverse Synthetic Aperture Radar (ISAR) imaging, it is possible to achieve much higher speed and less computational complexity. In this thesis, the formulation of the Multidimensional Dictionary Learning (MDDL) problem is expressed and six algorithms are proposed to solve it. The first one is based on the method of optimum directions (MOD) algorithm for 1D dictionary learning (1DDL), which uses alternating minimization and gradient projection approach. As the MDDL problem is non-convex, the second... 

Forward scatter radar is a special kind of bistatic radar. It is designed to detect targets near the transmitter-receiver line which is called baseline. It has a number of promising features such as larger target radar cross-section (RCS) than that of traditional radars, applicability of shadow inverse SAR (SISAR) algorithms, high performance in automatic target recognition and identification, and robustness to stealth technology. On the other hand, it also has some inherent limitations, including the absence of range resolution (potentially leading to a high Doppler clutter level) and operation within narrow angles relative to the transmitter-receiver baseline. Target detection in forward... 

Providing quality hospital services depends on the efficient and correct implementation of processes. Therapeutic care processes are a set of activities that are carried out with the aim of diagnosing, treating and preventing any disease in order to improve and promote the patient's health. The purpose of this study is to use process mining techniques to discover and improve healthcare processes. The case study of this research is a psychiatric hospital in Shiraz. The approach implemented in this research consists of three main stages including data pre-processing, model discovery phase, and analysis phase. Three algorithms including Heuristic Miner, Inductive Miner, and ILP Miner were used...