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Total 23 records

    Wide-band VHF nulling by five elements spiral array antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

    VHF-LB SDR phased array jamming resistant antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 442-445 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Emadi, M ; Esmi, N ; Mousavi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Genetic algorithm for optimization of beam forming in linear array antenna is used. The goal is to achieve a -30 dB null depth in pattern, with null steering capability over the frequency band. The simulation result is -85 dB that the SuperNEC results accepted this result by -56 dB Null Depth. Software Define Radio (SDR) Technology and digital I/Q modulator are used to implement the system. © 2006 IEEE  

    MIMO radar with phase-coded waveforms

    , Article Proceedings of IEEE East-West Design and Test Symposium, EWDTS 2013, Rostov-on-Don ; Septembe , 2013 , Page(s): 1 - 4 ; 9781479920969 (ISBN) Roshanzamir, A ; Bastani, M. H ; Sharif University of Technology
    2013
    Abstract
    A multiple input multiple output (MIMO) radar system, unlike a conventional phased array radar, can choose freely the signals which transmitted via its antennas to maximize the power around the locations of the specific targets, or more generally to approximate a given transmit beampattern, and also to minimize the cross-correlation of the signals reflected back to the radar by the targets of interest. In this paper we use of phase-coded signals and show how the above desirable features of MIMO radars with some operational consideration can help us to have a desire beampattern. We suppose that for a collection of phase-coded signals, the elements of transmitted signals cross-correlation... 

    Multi-hop communications on wireless network-on-chip using optimized phased-array antennas

    , Article Computers and Electrical Engineering ; Volume 39, Issue 7 , 2013 , Pages 2068-2085 ; 00457906 (ISSN) Tavakoli, E ; Tabandeh, M ; Kaffash, S ; Raahemi, B ; Sharif University of Technology
    2013
    Abstract
    Network-on-Chip (NoC) as a promising design approach for on-chip interconnect fabrics could overcome the energy as well as synchronization challenges of the conventional interconnects in the gigascale System-on-Chips (SoC); The advantages of communication performance of traditional wired NoC will no longer be continued by the future technology scaling. Packets that travel between distant nodes of a large scale wired on-chip network significantly suffer from energy dissipation and latency due to the routing overhead at each hop. According to the International Technology Roadmap for Semiconductors annual report, the RFCMOS characteristics will be steadily improved by technology scaling. As the... 

    Multipath effect on false peaks in covariance based MIMO radar beampattern design

    , Article Proceedings International Radar Symposium, Dresden ; Volume 2 , June , 2013 , Pages 970-975 ; 21555753 (ISSN) ; 9783954042234 (ISBN) Roshanzamir, A ; Bastani, M. H ; Sharif University of Technology
    2013
    Abstract
    In a Multiple Input Multiple Output (MIMO) radar unlike conventional phased array radar, we can choose freely between the probing signals transmitted via its antennas to maximize the transmitted power around specific target locations or to approximate a desire beam-pattern in different manners that many papers have taken into consideration so far. In an operational radar or communication environment, one of the usual phenomenon that happens is multipath. In this paper we'd like to take this effect into consideration and show that how this effect can influence our beam-pattern in a covariance based MIMO radar beam-forming. We will show that multipath can change beam-pattern peak direction,... 

    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) Roshanzamir, A ; 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... 

    Advantages of MIMO waveform in sidelobe blanker system

    , Article International Conference on Electronic Devices, Systems, and Applications ; 2012 , Pages 244-247 ; 21592047 (ISSN) ; 9781467321631 (ISBN) Roshanzamir, A ; Bastani, M. H ; Sharif University of Technology
    2012
    Abstract
    A multiple-input multiple-output (MIMO) radar system., unlike a standard phased array radar., can choose freely the probing signals transmitted via its antennas 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. In this paper it will be shown that how these more degrees of freedom to choose freely between probing signals in a MIMO radar can help to have an omnidirectional beam-pattern for a side-lobe blanker system., and it will be shown that with utilizing MIMO radars for a side-lobe blanker system.,... 

    Backhaul need for speed: 60 GHz is the solution

    , Article IEEE Wireless Communications ; Volume 22, Issue 6 , 2015 , Pages 114-121 ; 15361284 (ISSN) Verma, L ; Fakharzadeh, M ; Choi, S ; Sharif University of Technology
    Abstract
    The availability of 7-9 GHz of unlicensed spectrum at 60 GHz, advances in low-cost silicon technology, and high interference rejection due to atmospheric loss make 60 GHz an ideal solution for future 4G/5G small-cell backhaul links, where multi-gigabit rates are required. In this article, we review the 60 GHz propagation properties, the practical technology limits, and the regulatory and regional environmental impacts to present a framework for the 60 GHz backhaul link design that translates the link requirements to the essential transmitter and receiver system parameters. This approach includes a preliminary design that generates the input data set for an optimization problem. Two physical... 

    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) Tohidi, E ; 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... 

    Large Array Null Steering Using Compressed Sensing

    , Article IEEE Signal Processing Letters ; Volume 23, Issue 8 , 2016 , Pages 1032-1036 ; 10709908 (ISSN) Khosravi, M ; Fakharzadeh, M ; Bastani, M. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Abstract
    In this letter, array null steering is formulated as a sparse recovery problem. In addition, a novel null steering scheme for large arrays by perturbing only a few elements is presented. To achieve this goal, compressed sensing (CS) is used to exploit the sparsity of the perturbed elements. The advantages of the proposed scheme are a significant reduction in hardware cost and lower power consumption, as well as less aging of the elements and faster response. Simulation results show that the CS-based method could be efficiently used to generate wide nulls using at least two elements. The interference rejection ratio achieved by the proposed method is 10-20 dB better than the existing... 

    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) Mazaheri, M. H ; 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... 

    A novel algorithm in a linear phased array system for side lobe and grating lobe level reduction with large element spacing

    , Article Analog Integrated Circuits and Signal Processing ; Volume 104, Issue 3 , 13 March , 2020 , Pages 265-275 Khalilpour, J ; Ranjbar, J ; Karami, P ; Sharif University of Technology
    Springer  2020
    Abstract
    Phased array antennas are generally used for the inherent flexibility to beamforming and null-steering electronically. In the phased arrays the side lobes level (SLL) level is main problem which causes waste of energy or saturation of the receiver in the case of presence of the strong spatial blockers. In this paper, a weighting method was first used to reduce the level of SLL. However, this method increased the beam width and reduced resolution, which is not suitable for track applications. In next step hoping to increase the resolution, the distance between the antennas increased. But in this way, grating lobes appeared in the final beam. In fact, the main idea of the article is to solve... 

    A full 360° vector-sum phase shifter with very low rms phase error over a wide bandwidth

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 60, Issue 6 PART 1 , 2012 , Pages 1626-1634 ; 00189480 (ISSN) Asoodeh, A ; Atarodi, M ; Sharif University of Technology
    2012
    Abstract
    An innovative vector-sum phase shifter with a full 360° variable phase-shift range in 0.18-μm CMOS technology is proposed and experimentally demonstrated in this paper. It employs an I/Q network with high I/Q accuracy over a wide bandwidth to generate two quadrature basis vector differential signals. The fabricated chip operates in the 2.3-4.8 GHz range. The root-mean-square gain error and phase error are less than 1.1 dB and 1.4° over the measured frequency span, respectively. The total current consumption is 10.6 mA (phase shifter core: ∼2.6 mA) from a 1.8 V supply voltage and overall chip size is 0.87 × 0.75 mm 2. To the best of the authors' knowledge, this circuit is the first... 

    An optimized phased-array antenna for intra-chip communications

    , Article LAPC 2011 - 2011 Loughborough Antennas and Propagation Conference, 14 November 2011 through 15 November 2011 ; November , 2011 , Page(s): 1 - 4 ; 9781457710155 (ISBN) Tavakoli, E ; Tabandeh, M ; Kaffash, S ; Sharif University of Technology
    2011
    Abstract
    The continued migration to smaller nanometer geometries brought fundamental limits to traditional on-chip hard wires performance. According to the International Technology Roadmap for Semiconductor (ITRS), feature size shrinking leads an increase in the operating frequency of RFCMOS devices. Thus, new interconnect methodologies such as radio frequency (RF) wireless can be employed on future chips projected for intra-chip wireless data communications. The size of Si integrated antenna in these frequencies will be several millimetres and the antenna length will be decrease by frequency increasing. In this paper, we have proposed an optimum radiation pattern achieved by a phased array (PA)... 

    Fiber Bragg grating-based band edge delay line for radio frequency (RF) photonics applications

    , Article AEU - International Journal of Electronics and Communications ; Volume 64, Issue 3 , 2010 , Pages 267-272 ; 14348411 (ISSN) Rajabvand, M ; Behnia, F ; Sharif University of Technology
    2010
    Abstract
    A fiber Bragg grating (FBG)-based delay line (or phase shifter) has been developed for microwave over fiber and phased array antenna (PAA) applications. The scheme uses band edge time delay of tunable fiber gratings to provide a continuously controllable microwave time delay or phase shift. Following the formulation and analysis of the device behavior, simulations of amplitude and phase responses are conducted. The results confirm the validity of theoretical predictions  

    Phase-noise measurement of microwave oscillators using phase-shifterless delay-line discriminator

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 58, Issue 2 , January , 2010 , Pages 468-477 ; 00189480 (ISSN) Gheidi, H ; Banai, A ; Sharif University of Technology
    2010
    Abstract
    In this paper, a modified method based on the frequency discriminator technique for measuring phase noise of microwave oscillators is presented. In the proposed method, the phase shifter is omitted. In contrast, a 90° hybrid with one more channel containing a phase detector, and a low-noise amplifier is added to the measurement setup. It can be said that an in-phase/quadrature phase-noise detection has been developed. With the proposed method, tuning of the variable phase shifter is not needed anymore. Therefore, the measurement is done automatically, and as a result, the measurement time is decreased. Another considerable advantage of this method is that the method is theoretically... 

    Low-cost three-dimensional millimeter-wave holographic imaging system based on a frequency-scanning antenna

    , Article Applied Optics ; Volume 57, Issue 1 , 2018 , Pages A65-A75 ; 1559128X (ISSN) Nili, V. A ; Mansouri, E ; Kavehvash, Z ; Fakharzadeh, M ; Shabany, M ; Khavasi, A ; Sharif University of Technology
    OSA - The Optical Society  2018
    Abstract
    In this paper, a closed-form two-dimensional reconstruction technique for hybrid frequency and mechanical scanning millimeter-wave (MMW) imaging systems is proposed. Although being commercially implemented in many imaging systems as a low-cost real-time solution, the results of frequency scanning systems have been reconstructed numerically or have been reported as the captured raw data with no clear details. Furthermore, this paper proposes a new framework to utilize the captured data of different frequencies for three-dimensional (3D) reconstruction based on novel proposed closed-form relations. The hybrid frequency and mechanical scanning structure, together with the proposed... 

    Beamforming, null-steering, and simultaneous spatial and frequency domain filtering in integrated phased array systems

    , Article AEU - International Journal of Electronics and Communications ; Volume 110 , 2019 ; 14348411 (ISSN) Karami, P ; Atarodi, S. M ; Sharif University of Technology
    Elsevier GmbH  2019
    Abstract
    In the case that phased array systems are not capable of attenuating interferences, Radio Frequency (RF) front-ends and Analog Digital Converters (ADCs) with a large dynamic range are required to avoid saturation of the receiver. This leads to a higher power consumption. In this paper, employing N-path circuits in Mixer-First receivers, a novel method is introduced in which spatial and frequency blockers are eliminated right before entering the system on the antennas input. In fact using this technique, adjustable spatial notch filter and band-pass frequency filter are implemented to suppress spatial and frequency interferences. The proposed method enhances the robustness and effectiveness... 

    Asymmetrical 4×4 butler matrix and its application for single layer 8×8 butler matrix

    , Article IEEE Transactions on Antennas and Propagation ; Volume 67, Issue 8 , 2019 , Pages 5372-5379 ; 0018926X (ISSN) Tajik, A ; Shafiei Alavijeh, A ; Fakharzadeh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    The design procedure and measured results of a novel 4 × 4 Butler matrix are presented in this paper. This asymmetrical structure provides fairly flexible phase outputs; therefore, the array radiation pattern can be rotated around the array normal axis. The structure of this modified Butler matrix is discussed in detail, and the explicit design formulas are derived to achieve the arbitrary main beams direction. Using the proposed design procedure, the Butler matrix can provide even broadside and endfire beams. In addition, this structure is employed to design two Butler matrices, which generate similar patterns as a conventional 8 × 8 Butler matrix, using only single layer circuits with... 

    5-6 GHz dual-vector phase shifter in 0.18 μm LID CMOS

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 82-86 ; 9781728115085 (ISBN) Choopani, A ; Fakharzadeh, M ; Safarian, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    In this paper, a low power active phase shifter in 0.18 μm CMOS technology, operating from 5 to 6 GHz, for WLAN applications is presented. Design equations for this novel structure, which consists of two current steering stages, transconductance stage and DACs, are derived, thoroughly. This phase shifter has a range of 360° with 5.625° phase resolution. The power consumption is 35 mW. The RMS phase error is only 0.3°. The simulated power gain, input P1dB, and NF are 4 dB, -0.8 dBm and 6 dB, respectively