Sharif Digital Repository

Range Profile (RP) is known as one of the most important tools for radar target recognition. The main problem with range profile for radar target recognition is its sensitivity to aspect angle. To overcome this problem, range profiles are assumed to have the same statistical characteristics in small frames of aspect angles or context dependent models such as HMM may be used. All methods presented, seems to have some shortcomings to offer a model based on physical circumstances of target maneuver. For example in such models, consecutive samples of RPs in an aspect frame are assumed to be statistically independent with the same distribution (IID). Here we propose dynamic system (DS) for... 

Although up to now different processing algorithms have been proposed for Synthetic Aperture Radar (SAR) raw data, all of them suffer from one common problem and that is huge amount of data to be processed. So because of current system limitations, efficient compression algorithms for processing, saving, or transmitting data are needed. Up to now many algorithms have been proposed for SAR raw data compression, but each of them has some defects that should be payed attention to. The most important reason of these defects is the special characteristics of SAR images. With the aid of “Compressed Sensing (CS)”, the new field which has emerged recently, a special characteristic of the scene... 

Studies regarding Multiple Input - Multiple Output synthetic aperture radars, shows promising advances in synthetic aperture imaging. Compared to conventional SAR, MIMO-SAR encompasses desirable features, namely: lower background noise, better detection rate, easier implementation of imaging modes etc. Signals used in these radars, are required to have specific properties such as orthogonality, large time-bandwidth product, high Doppler tolerance and qualified ambiguity function. Also because of the specific geometry of SAR imaging, these signals should remain orthogonal in respectively large Doppler shifts and time offsets. Through the past years, many signals are suggested in the... 

Sparse representation and compressed sensing have been widely used in various fields, one of the most popular of which is ISAR imaging. Inverse Synthetic Aperture Radar (ISAR) provides an electromagnetic image of the target, which is mainly used to identify and classify targets. In some applications, recognizing targets from a 2D image can be difficult and error-prone. One idea to deal with this problem is 3D ISAR imaging. The most widely used method of ISAR imaging is direct method based on Fourier transform. This method requires the measurement of radar data with high measurement density in 3 directions, which increases the data collection time and volume, which is the main problem of... 

In this thesis we consider the effect of random locations of users in the capacity analysis of SIR-based power control systems and comparison to the strength-based systems, for the first time. Unlike previous works we do not consider a simple deterministic uniform model for the analysis. We provide simulations and analytical solutions for calculating the interference statistics, based on which, we not only calculate the interference statistics, but also study the effect of locating a user in every location in the network coverage area and its share in the interference. We also calculate each cell’s share in every statistics of the interference. In this thesis, based on the common assumption... 

In synthetic aperture radar (SAR) satellites, the nadir echo is defined as the backscattered signal from the point directly below the satellite on the earth surface. If the timing of the radar is such that the nadir echo arrives at the receiver while the receiver is turned on for receiving the desired signal, it could damage the receiver or disrupt the resulting SAR image, unless it is suppressed enough by proper design of antenna radiation pattern. In current SAR satellites, ”avoiding” this phenomenon is associated with two problems: 1) limiting the swath width, 2) imposing stringent restrictions on the selection of pulse repeatition frequency (PRF). Therefore, ”suppressing” the nadir echo,... 

Localization of radio sources has various applications in civil and military communications. Some of important localization methods consist of Angle of Arrival (AoA) estimation of the illuminated signals from the interested sources. Between various Direction Finding (DF) methods, subspace based methods are of special importance, because of their high resolution and accuracy. And from beginning of invention, because of new challenges, have been focus of numerous researches. In this thesis, first we explain the most important subspace based DF methods called MUSIC and root-MUSIC. Then a novel modification for root-MUSIC is introduced. In our new method the computational complexity of... 

During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of... 

Multiple Input Multiple Output (MIMO) radar is an emerging technology which has attracted many researchers recently. The problem of beampattern design of a MIMO radar in uniform arrays and with the covariance based method of point targets has been investigated by many papers so far. In this thesis it is desirable to consider this problem in non-uniform arrays. Many authors have designed the transmitted beampattern by means of designing the cross correlation matrix of transmitted signals elements, but in this paper optimizing the locations of transmitted antennas will be done as well as cross correlation matrix of transmitted signals to achieve a better results  

One of the subsets of the radar systems is recognition of targets. Radar Target Recognition (RTR) is a process in which a target is distinguished from a set of targets. To recognize radar targets, we need to extract useful information from the returned signal from them. The most important issues in recognizing radar targets are the selection of information that reduces the amount of information needed for the identification process, the ease of extracting information from the moving target, and the ease of decision making to determine the identity of the target. One method is to produce a high resolution range profile, which is the one-dimensional image of the target in the direction of... 

Target recognition is one of the widespread applications of today's radars that requires obtaining target signatures using radar measurements. High-resolution range profile (HRRP) is one of these signatures that provides a one-dimensional radar image of the target. There are several methods for radar target's HRRP synthesis , all of which require a large bandwidth. One of these methods is the use of stepped frequency radar. One of the advantages of this method is providing a wide bandwidth by sending pulses with small bandwidths, thus obviating the need for broadband receivers and transmitters and making implementation easier. In many cases HRRP of target is sparse, because the number of... 

Pulse compression techniques such as linear frequency modulation (LFM) and phase-coded pulse are an active research topic in radar systems, spread spectrum communication applications, etc. Pulse compression technique is employed to achieve high range resolution with enough low average power. A problem in pulse compression is masking of small targets by the range sidelobes of large nearby targets. Furthermore, the range sidelobes may be detected as separate targets and thus increase the false alarm. The most popular waveform among pulse compression techniques is the LFM (also known as chirp). However, the LFM waveform is susceptible to electronic warfare; hence using the biphase coded... 

Monopulse radar with amplitude compression is among the most important radars used for tracking. This thesis analyzes errors in monopulse radar. There are four main errors in monopulse radar. These errors are 1- receiver noise 2-glint noise 3-servo noise 4-imbulance in receivers. In this thesis we have compared noise effect in swirling type 1 and swirling type 2 targets. Glint phenomenon is the most important error in monopulse radar which becomes the main source error in close targets. Frequency agility was chosen as an initial step to implement the tracking improvement. In this method several pulses have been used and the position corresponding to the return with the largest amplitude for... 

Due to multiple transmit-receive channels, the signal model in a MIMO radar system is usually described by high dimensional data structures. However, the desired target space (e.g. range-azimuth domain) which shall be estimated, is mainly sparse (the number of existing targets is usually small). This observation has promoted the use of sparse recovery methods in multi-target detection and estimation in such radar systems which led to introducing the concept of compressive sensing (CS) based MIMO radars. Successful implementation of CS techniques for recovery of radar scenes (for target detection/estimation) from the received noisy measurements strongly entails that the associated sensing... 

- Pulse-compression is one of the spread spectrum techniques that allows a radar to simultaneously achieve the energy of a long pulse and the resolution of a short pulse. The long pulse band-width is increased by phase or frequency modulation, then this modulated long pulse is compressed by matched filter of the receiver. A simple class of pulse-compression waveforms is Binary phase-coded pulse that uses rectangular sub pulses. When the transmitted signal encounters a moving target, the performance of radar degrades due to Doppler frequency shift of received signal. Binary codes have high side lobe levels for long Codes, so to solve this problem the Quadriphase-coded pulse that constructed... 

Transmit waveform plays a significant role in active sensing systems. High speed and off-the-shelf processors, digital arbitrary waveform generators, and solid state transmitters have paved the way for an increased capability to adapt the transmit signal and the receive fil-ters with respect to (w.r.t.) the illuminated environment. In this thesis, we have considered the waveform design problem for different scenarios, in two parts. Firstly, we have con-sidered the problem for the extended target model in single-input single-output (SISO) radars. There, we have assumed known target impulse response (TIR) with an unknown reflection factor and found the waveform corresponding to the optimal... 

One of non-cooperative illuminators recently considered for passive radar application is the DVB-T signal. Its thumbtack ambiguity function beside the constancy over time makes it very desirable. But there are some ambiguities in its ambiguity function that can not be neglected. In this paper, after studying the reasons of the ambiguities we propose some processings to remove them. It is shown that for removing the ambiguities, it’s sufficient to filter out continual pilots and equalize scattered pilots. The results show that an ambiguity function relatively without ambiguities will be obtained. A method for compensating the target’s range migration-that results in processing gain decrease... 

Phenolic compounds are important environmental pollutants that the removal and separation of them from the water and industrial wastewater especially in the oil industry is essential before entering the environment. In the present study, the removal efficiency of the adsorbent silica aerogel 4-Chlorophenol and 4-Bromophenol as phenolic compounds from aqueous solution was surveyed. In this research, the effects of various factors such as contact time, pH, and initial concentration of the pollutant and the adsorbent on the adsorption were studied. It was observed that there is a large amount of adsorption in acidic pH and this amount increases by incrementing the concentration of the... 

Employing array of antennas in amny signal processing application has received considerable attention in recent years due to major advances in design and implementation of large dimentional antennas. In many applications we deal with such large dimentional antennas which challenge the traditional signal processing algorithms. Since most of traditional signal processing algorithms assume that the number of samples is much more than the number of array elements while it is not possible to collect so many samples due to hardware and time constraints.
In this thesis we exploit new results in random matrix theory to charachterize and describe the properties of Sample Covariance Matrices... 

Adaptive beamforming performance is very sensitive to any mismatch between actual and presumed steering vectors of desired signal. In addition to this sensitivity, presence of desired signal in training snapshots dramatically reduces the convergence rate, as compared to the case that signal-free training snapshots are available.
The present work is aimed at proposing a new adaptive beamformer that is robust against direction-of-arrival (DOA) mismatch and has high convergence rate. This method is based on desired signal elimination from training snapshots and sub-array beamforming technique. To this end, a Blocking matrix that converts primary data to desired signal free data is...