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A Comparative Study of Several Array Geometries for 2D DOA Estimation
, Article Procedia Computer Science, 102015 through 13 August 2015 ; Volume 58 , August , 2015 , Pages 18-25 ; 18770509 (ISSN) ; Pezeshk, A. M ; Thampi S. M ; James A. P ; Al Jumeily D ; Sharif University of Technology
Elsevier
2015
Abstract
In this paper, a comparison between several array geometries, including planar arrays and volume arrays, for two-dimensional Direction of Arrival (DOA) estimation using Multiple Signal Classification (MUSIC) is presented. For each geometry, various criteria is taken into consideration and a comparative study of the performance of geometries is carried out. The geometries together with their ultimate direction finding performance are compared based on Root Mean Square Error (RMSE), the ambiguity functions, and Cramer-Rao Bounds (CRB). Furthermore, the effects of phase and amplitude variations of the array element radiation pattern, namely Vivaldi and Monopole antenna, on DOA estimation...
Reduced active impedance variation by using time modulated array
, Article 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019, 7 July 2019 through 12 July 2019 ; 2019 , Pages 1765-1766 ; 9781728106922 (ISBN) ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; IEEE Antennas and Propagation Society (APS); The Institute of Electrical and Electronics Engineers (IEEE) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper we investigate the active impedance of Time Modulated Array (TMA) as a low-cost and simple beamforming architecture. Since the antenna elements in TMA are periodically turned on and off, the active impedance of this structure has less variation compared to a phased array architecture. In this paper, we have compared the active impedance of a TMA structure and that of the phased array for different cases. The active reflection coefficient of the TMA is always below-10 dB, while the impedance of the phased array becomes unmatched for certain scan angles
Sidelobe level optimization using modified genetic algorithm
, Article IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) ; Volume 1 , 2002 , Pages 742-745 ; 15223965 (ISSN) ; Rashed Mohassel, J ; Sharif University of Technology
2002
Abstract
The sidelobe level (SLL) of a linear array is optimized using modified continuous genetic algorithms (GAs) in this work. The amplitude and phase of the current as well as the separation of the antennas are all taken as variables to be controlled. The results of the design using modified GA versions are compared with other methods. Two design problems were studied several continuous modified GA version and the results are presented as several plots. As a final example, the design specifications for an array with 200 elements is given. The effectiveness and advantages of the modified GA version is outlined
Instrumentation development for an array of water cherenkov detectors for extensive air shower experiments
, Article Journal of Physics G: Nuclear and Particle Physics ; Volume 36, Issue 11 , 2009 ; 09543899 (ISSN) ; Bahmanabadi, M ; Keivani, A ; Samimi, J ; Sharif University of Technology
2009
Abstract
A new small array of Cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains four tanks of distilled water with a diameter of 64 cm and a height of 130 cm. The effective area of each tank is about 1382 cm2. They are used to detect air showers and to record the arrival time of the secondary particles. We have collected about 640 000 extensive air showers (EAS) in 8298 h of observation time from November 2006 to October 2007. The distribution of air showers in zenith and azimuth angles has been studied and a cosn distribution with n = 6.02 0.01 was obtained for the zenith angle distribution. An asymmetry has been observed in the azimuthal distribution of...
Superconductivity transition dependence of the thermal crosstalk in YBa 2Cu 3O 7-x edge-transition bolometer arrays
, Article IEEE Transactions on Applied Superconductivity ; Volume 16, Issue 1 , 2006 , Pages 9-14 ; 10518223 (ISSN) ; Fardmanesh, M ; Schubert, J ; Banzet, M ; Sharif University of Technology
2006
Abstract
The effect of the superconductivity transition on the thermal crosstalk in YBa 2Cu 3O 7-x, edge-transition bolometer arrays is investigated for DC to midrange modulation frequency infrared radiation. The bolometers in the arrays were designed with various distances on SrTiO 3 (100) substrates. We have observed a change in the thermal crosstalk between neighbor devices through the superconductivity transition temperature range. Superconductivity transition dependence of the thermal coupling between the devices was measured by utilizing the thermal conductance measurement methods developed for the bulk material. The knee points in the magnitude of the response versus modulation frequency...
Broadband miniaturized efficient array antennas
, Article Applied Computational Electromagnetics Society Journal ; Volume 28, Issue 3 , 2013 , Pages 188-194 ; 10544887 (ISSN) ; Jafargholi, A ; Sharif University of Technology
2013
Abstract
This paper introduces a new array architecture, in which antenna elements are arranged in a spiral curve. The spiral array enhances ultra-wideband (UWB) pattern characteristics compared to alternative array geometries of similar elements, without requiring a complex feed network for frequency change compensation. A number of examples are illustrated to demonstrate the array capability in broadband array designs. It is revealed that for the same number of elements and curvature lengths, a spiral array has a wider radiation bandwidth than the corresponding circular and linear array antennas. In addition, it is also demonstrated that the spiral architecture discussed here can be best suited for...
A figure of merit in a time-modulated array
, Article IEEE Antennas and Wireless Propagation Letters ; Volume 18, Issue 10 , 2019 , Pages 2086-2089 ; 15361225 (ISSN) ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this letter, we use G/T as a figure of merit to evaluate the performance of time-modulated arrays (TMA). The noise performance of a receiver, which is periodically switched on and off, is quite different from that of a conventional receiver. We analytically investigate the noise performance of a TMA. Based on this analysis, the figure of merit, G/T, of the TMA structure is investigated, including the details of the receiver hardware. Moreover, the G/T of the TMA is compared with that of a phased array. The comparison indicates that the TMA structure provides the same or even better performance compared to a phased array system, which demonstrates the capability of TMA in providing...
Multiple target parameter estimation in multi-frequency array radar
, Article International Review of Electrical Engineering ; Volume 5, Issue 6 , Nov/Dec , 2010 , Pages 2692-2709 ; 18276660 (ISSN) ; Nayebi, M. M ; Amindavar, H. R ; Sharif University of Technology
2010
Abstract
Since space diversity and frequency diversity are both efficient techniques in the radar applications, we propose in this paper a method for simultaneous usage of both techniques. On this basis, multi-frequency array radar in which all frequencies are used simultaneously to increase the number of targets that can be uniquely identified, is introduced and analyzed. First, the signal model for such a system is derived and then, it is shown how the use of multi-frequency signal can noticeably improve the parameter identifiability. Specifically, we show the maximum number of targets that can be uniquely identified by the multi-frequency array radar is L times that of its single-frequency array...
Transversals in long rectangular arrays
, Article Discrete Mathematics ; Volume 306, Issue 23 SPEC. ISS , 2006 , Pages 3011-3013 ; 0012365X (ISSN) ; Etesami, O ; Mahini, H ; Mahmoody, M ; Sharifi, A ; Sharif University of Technology
Elsevier
2006
Abstract
In this paper it is shown that every m × n array in which each symbol appears at most (mn - 1) / (m - 1) times has a transversal, when n ≥ 2 m3. © 2006 Elsevier B.V. All rights reserved
Investigation of the locking bandwidth in linear and circular arrays of mutually coupled oscillators, intended for microwave power combining
, Article IEE Proceedings: Microwaves, Antennas and Propagation ; Volume 152, Issue 6 , 2005 , Pages 441-448 ; 13502417 (ISSN) ; Farzaneh, F ; Ayazian, S ; Sharif University of Technology
2005
Abstract
An array of N weakly coupled oscillators is investigated in two major configurations. The locking bandwidth for linear and circular arrays is assessed through an array coupling matrix, in a worst-case free-running frequency distribution of oscillators. The superior locking bandwidth for circular arrays is demonstrated
Optimization of array factor in linear arrays using modified genetic algorithm
, Article International Journal of Engineering, Transactions B: Applications ; Volume 17, Issue 4 , 2004 , Pages 369-379 ; 1728-144X (ISSN) ; Rashed Mohassel, J ; Mafinezhad, K ; Sharif University of Technology
Materials and Energy Research Center
2004
Abstract
The array factor (sidelobe level, SLL) of a linear array is optimized using modified continuous genetic algorithms in this work. The amplitudes and phases of the currents as well as the separation of the antennas are all taken as variables to be controlled. The results of the design using modified GA versions are compared with other methods. Two design problems were studied using several continuous modified GA versions and the results are presented as several plots. As a final example, the design specifications for an array with 200 elements are given. The effectiveness and advantages of the proposed modified GA versions are outlined
Hybrid orthogonal-phased array MIMO RADAR
, Article IET Conference Publications ; Volume 2013, Issue 617 CP , 2013 ; 9781849196031 (ISBN) ; Bastani, M. H ; Sharif University of Technology
2013
Abstract
Multiple Input Multiple Output (MIMO) radar is a multiple aperture technology characterized by the ability to transmit diverse signals at each aperture. This is in contrast to traditional phased array radar whereby a single signals is transmitted with a phase shift applied at each element to enable steering of the transmit beampattern. The hybrid MIMO phased array radar (HMPAR) concept is an outgrowth of the monostatic MIMO construct, in which all sensors have the same view of the far field target which is known as colocated antenna. In the HMPAR, the full transmit array is partitioned into sub-arrays which can be electronically steered in different directions and driven by separate transmit...
Phased array radar beamforming method based on MIMO radar covariance
, Article IET Conference Publications ; Volume 2013, Issue 617 CP , 2013 ; 9781849196031 (ISBN) ; Bastani, M. H ; Sharif University of Technology
2013
Abstract
A multiple input multiple output (MIMO) radar is an emerging field which has attracted many researchers recently. In this type of radar, unlike an standard phased array radar, one can choose transmitted probing signals freely to maximize the power around the locations of the targets of interest, or more generally to approximate a given transmit beam-pattern, or to minimize the cross-correlation of the signals reflected back to the radar by the targets of interest. These signals can be correlated to each other or noncorrelated. Many papers have investigated beampattern design and waveforming in MIMO radars. One of the most famous approaches for beampattern design is named covariance based...
Analysing of 3D beamforming in MIMO radars
, Article Proceedings of the 2012 World Congress on Information and Communication Technologies, WICT 2012 ; 2012 , Pages 745-749 ; 9781467348041 (ISBN) ; Bastani, M. H ; Roshanzamir, M ; Machine Intelligence Research Labs (MIR Labs) ; Sharif University of Technology
2012
Abstract
A multiple input multiple output (MIMO) radar system is an emerging research field which has attracted many studies in recent years. This type of radar, unlike conventional phased array radar, can transmit different probing signals via its antennas, that may be correlated or uncorrelated with each other. This waveform diversity offered by MIMO radar systems enable superior capabilities compared to conventional phased array radar. Many papers have introduced different ways for beamforming of MIMO radar. In this paper it is desirable to analysis some methods for beamforming of MIMO radars with planar arrays constellation and examine their 3D result beam-pattern of such constellations for...
A linear algebraic approach to orthogonal arrays and Latin squares
, Article Ars Combinatoria ; Volume 105 , 2012 , Pages 3-13 ; 03817032 (ISSN) ; Mahdian, M ; Mahmoodian, E. S ; Sharif University of Technology
2012
Abstract
To study orthogonal arrays and signed orthogonal arrays, Ray-Chaudhuri and Singhi (1988 and 1994) considered some module spaces. Here, using a linear algebraic approach we define an inclusion matrix and find its rank. In the special case of Latin squares we show that there is a straightforward algorithm for generating a basis for this matrix using the so-called intercalates. We also extend this last idea. Copyright
Evaluation of beam steering in circular planar array of coupled microwave oscillators
, Article International Journal of RF and Microwave Computer-Aided Engineering ; Volume 21, Issue 4 , 2011 , Pages 383-391 ; 10964290 (ISSN) ; Banai, A ; Farzaneh, F ; Sharif University of Technology
2011
Abstract
A Green's function to describe the time behavior of the locking phases in a circular planar array of mutually coupled microwave oscillators is proposed. Using this Green's function the dynamic behavior of the array can be described for any arbitrary free running frequency of elements of the oscillator array. Beam steering is realized via detuning the edge oscillators of the array from a reference frequency and the beam direction is controlled by the amount of detuning for each oscillator at the edge. Some detuning functions such as sinusoidal, triangular and rectangular ones have been applied and, the resulting array patterns are compared with one another
A fast and novel method of pattern synthesis for non-uniform phased array antennas
, Article Proceedings International Radar Symposium, 24 June 2015 through 26 June 2015 ; Volume 2015-August , 2015 , Pages 924-929 ; 21555753 (ISSN) ; 9783954048533 (ISBN); 9783954048533 (ISBN); 9783954048533 (ISBN) ; Sebt, M. A ; Nayebi, M. M ; Behroozi, H ; Rohling, H ; Rohling, H ; Rohling, H ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
Weighting elements to achieve radiation patterns with desired characteristics is a classical work in phased array antennas. These characteristics can be low sidelobe level, narrow beamwidth, high directivity, pattern nulling in special angle and etc. For each of these characteristics, different methods have been introduced. Most of methods have been presented for uniform arrays, however there are lots of methods to obtain a desired pattern for antennas with non-uniform element distances. The problem with these methods is complexity or not very good results. In this paper, fast and easy methods based on Least Square Error that leads to good results are presented. In addition, weighting of...
Anti-aggregation of gold nanoparticles for metal ion discrimination: a promising strategy to design colorimetric sensor arrays
, Article Sensors and Actuators, B: Chemical ; Volume 270 , 2018 , Pages 545-551 ; 09254005 (ISSN) ; Ghasemi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
Abstract
The first report of anti-aggregation-based sensor arrays is presented. The strategy is based on the competitive interaction of citrate-capped gold nanoparticles (AuNPs) and heavy metal ions (i.e., Hg(II), Ag(I), Fe(III), and Pb(II)) with three aggregation reagents (i.e., cysteine, melamine, and arginine). In the presence of aggregation reagent, the color and UV–vis spectra of AuNPs are changed indicating the aggregation of AuNPs. Addition of the aggregation reagents which are firstly treated with the ions, causes AuNPs turn from the aggregation to the dispersion state. The anti-aggregation capability of ions towards various aggregation reagents is different because of distinct stability...
A route to unusually broadband plasmonic absorption spanning from visible to mid-infrared
, Article Plasmonics ; Volume 14, Issue 5 , 2019 , Pages 1269-1281 ; 15571955 (ISSN) ; Khavasi, A ; Serebryannikov, A.E ; Vandenbosch, G. A. E ; Ozbay, E ; Sharif University of Technology
Springer New York LLC
2019
Abstract
In this paper, a route to ultra-broadband absorption is suggested and demonstrated by a feasible design. The high absorption regime (absorption above 90%) for the suggested structure ranges from visible to mid-infrared (MIR), i.e., for the wavelength varying from 478 to 3278 nm that yields an ultra-wide band with the width of 2800 nm. The structure consists of a top-layer-patterned metal-insulator-metal (MIM) configuration, into the insulator layer of which, an ultra-thin 5 nm layer of manganese (Mn) is embedded. The MIM configuration represents a Ti-Al2O3-Ti tri-layer. It is shown that, without the ultra-thin layer of Mn, the absorption bandwidth is reduced to 274 nm. Therefore, adding only...
Vapor absorption into liquid films flowing over a column of cooled horizontal tubes
, Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 332-338 ; 10263098 (ISSN) ; Babadi, F ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
In this paper, a theoretical analysis of the combined heat and mass transfer over cooled horizontal tubes is presented. The boundary layer assumptions are used for the transport of mass, momentum and energy equations and the finite difference method is employed to solve the governing equations in the absorber tube bundle. The effects of important parameters, such as solution flow rate, absorber pressure and tube radius, are discussed on the overall heat and mass transfer for a tube and tube bundle. © Sharif University of Technology, October 2004