Dissertations / Theses on the topic 'Arrays'
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Albannay, Mohammed Masoud. "Array of antenna arrays." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/75576/1/Mohammed_Albannay_Thesis.pdf.
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Antenna arrays are groups of antenna elements spaced in a geometrical pattern. By changing the phase excitation of each element, the array is capable of transmitting electromagnetic waves strongly in a chosen direction with little or no radiation in another direction, thus controlling the array's radiation pattern without physically moving any parts. An antenna array of sub-arrays replaces conventional antenna elements with compact circular arrays with potential for improved performance.
This thesis expands on the concept by exploring the development, realisation and operation of an array of subarrays. The overall size of the array essentially remains the same, but the array's performance is improved due to having steerable directive subarrays. The negative effects of strong mutual coupling between closely spaced elements of a subarray are analysed and a number of new solutions for element decoupling are proposed.
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Tzanidis, Ioannis. "Ultrawideband Low-Profile Arrays of Tightly Coupled Antenna Elements: Excitation, Termination and Feeding Methods." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316439948.
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Khan, Iqtidar Ahmad. "Analysis and Synthesis of a New Class of Low Side Lobe Planar Arrays." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/93222.
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Numerical techniques for designing planar arrays with low side lobe level often require memory intensive optimization algorithms and also initialization in the form of some known values of radiation pattern parameters beforehand - information that may not be available when designing arrays. A few analytical methods exist in the literature that can be used to design rectangular lattices of isotropic elements for desired half-power beamwidth and side lobe level, but the number of elements of the array often should be known before the design process. Some array designs based on analytical techniques may suffer from severe performance limitations, an example is the uniformly excited array which cannot produce side lobe levels below ̶13.3 dB.
The goal of this study is to present an analytical technique for synthesis of planar arrays that, for specified radiation pattern requirements, not only provides quick solutions for the required number of elements and its distribution along the length and width of the array rectangular lattice, but also produces low side lobes without any limitation. A new class of non-uniformly excited equally spaced planar arrays is introduced and investigated in this study. The new array uses the patterns of uniformly excited linear arrays as its building blocks and has a separable element current distribution, hence making it mathematically convenient to analyze its radiation properties in terms of those of its constituent linear arrays. The proposed planar array does not suffer from the side lobe level limitation of uniformly excited planar arrays, and its synthesis, due to the analytical nature of description of its radiation properties, does not require iterative procedures that are inherent to numerical techniques.
Radiation characteristics of the proposed planar array, including directivity, side lobe level, half-power beamwidths, far-field three dimensional radiation patterns, and element excitation currents, are examined and simulation results for several example cases are presented. The analysis culminates with successfully mapping a continuous radiation pattern to discrete element currents in a rectangular lattice geometry.
The synthesis procedure is validated by successfully designing various planar arrays with desired requirements in terms of side lobe level and half-power beamwidths in the principal planes. Several design examples are presented. Radiation characteristics of the synthesized arrays are compared with the desired design requirements which were used as input information in the synthesis process. For the cases studied, the achieved performance characteristics are close to the desired ones.MS
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范世鳴 and Sai-ming Fan. "On m-arrays and M-arrays." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31207248.
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Alsawaha, Hamad Waled. "Synthesis of Ultra-Wideband Array Antennas." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54553.
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Acquisition of ultra-wideband signals by means of array antennas requires essentially frequency-independent radiation characteristics over the entire bandwidth of the signal in order to avoid distortions. Factors contributing to bandwidth limitation of arrays include array factor, radiation characteristics of the array element, and inter-element mutual coupling. Strictly speaking, distortion-free transmission or reception of ultra-wideband signals can be maintained if the magnitude of the radiated field of the array remains constant while its phase varies linearly with frequency over the bandwidth of interest. The existing wideband-array synthesis methods do not account for all factors affecting the array bandwidth and are often limited to considering the array factor and not the total field of the array in the synthesis process.
The goal of this study is to present an ultra-wideband array synthesis technique taking into account all frequency-dependent properties, including array total pattern, phase of the total radiated field, element field, element input impedance, and inter-element mutual coupling. The proposed array synthesis technique is based on the utilization of frequency-adaptive element excitations in conjunction with expressing the total radiated field of the array as a complex Fourier series. Using the proposed method, element excitation currents required for achieving a desired radiation pattern, while compensating for frequency variations of the element radiation characteristics and the inter-element mutual coupling, are calculated.
An important consideration in the proposed ultra-wideband array design is that the "phase bandwidth", defined as the frequency range over which the phase of the total radiated field of the array varies linearly with frequency, is taken into account as a design requirement in the synthesis process. Design examples of linear arrays with desired radiation patterns that are expected to remain unchanged over the bandwidth of interest are presented and simulated. Two example arrays, one with a wire dipole as its element and another using an elliptically-shaped disc dipole as the element are studied. Simulation results for far-field patterns, magnitude and phase characteristics, and other performance criteria such as side-lobe level and scanning range are presented.
Synthesis of two-dimensional planar arrays is carried out by employing the formulations developed for linear arrays but generalized to accommodate the geometry of planar rectangular arrays. As example designs, planar arrays with wire dipoles and elliptical-shaped disc dipoles are studied. The simulation results indicate that synthesis of ultra-wideband arrays can be accomplished successfully using the technique presented in this work. The proposed technique is robust and comprehensive, nonetheless it is understood that the achieved performance of a synthesized array and how closely the desired performance is met also depends on some of the choices the array designer makes and other constraints, such as number of elements, type of element, size, and ultimately cost.Ph. D.
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Jafri, Ahsan. "Array signal processing based on traditional and sparse arrays." Thesis, University of Sheffield, 2019. http://etheses.whiterose.ac.uk/23072/.
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Array signal processing is based on using an array of sensors to receive the impinging signals. The received data is either spatially filtered to focus the signals from a desired direction or it may be used for estimating a parameter of source signal like direction of arrival (DOA), polarization and source power. Spatial filtering also known as beamforming and DOA estimation are integral parts of array signal processing and this thesis is aimed at solving some key probems related to these two areas. Wideband beamforming holds numerous applications in the bandwidth hungry data traffic of present day world. Several techniques exist to design fixed wideband beamformers based on traditional arrays like uniform linear array (ULA). Among these techniques, least squares based eigenfilter method is a key technique which has been used extensively in filter and wideband beamformer design. The first contribution of this thesis comes in the form of critically analyzing the standard eigenfilter method where a serious flaw in the design formulation is highlighted which generates inconsistent design performance, and an additional constraint is added to stabilize the achieved design. Simulation results show the validity and significance of the proposed method. Traditional arrays based on ULAs have limited applications in array signal processing due to the large number of sensors required and this problem has been addressed by the application of sparse arrays. Sparse arrays have been exploited from the perspective of their difference co-array structures which provide significantly higher number of degrees of freedoms (DOFs) compared to ULAs for the same number of sensors. These DOFs (consecutive and unique lags) are utilized in the application of DOA estimation with the help of difference co-array based DOA estimators. Several types of sparse arrays include minimum redundancy array (MRA), minimum hole array (MHA), nested array, prototype coprime array, conventional coprime array, coprime array with compressed interelement spacing (CACIS), coprime array with displaced subarrays (CADiS) and super nested array. As a second contribution of this thesis, a new sparse array termed thinned coprime array (TCA) is proposed which holds all the properties of a conventional coprime array but with $\ceil*{\frac{M}{2}}$ fewer sensors where $M$ is the number of sensors of a subarray in the conventional structure. TCA possesses improved level of sparsity and is robust against mutual coupling compared to other sparse arrays. In addition, TCA holds higher number of DOFs utilizable for DOA estimation using variety of methods. TCA also shows lower estimation error compared to super nested arrays and MRA with increasing array size. Although TCA holds numerous desirable features, the number of unique lags offered by TCA are close to the sparsest CADiS and nested array and significantly lower than MRA which limits the estimation error performance offered by TCA through (compressive sensing) CS-based methods. In this direction, the structure of TCA is studied to explore the possibility of an array which can provide significantly higher number of unique lags with improved sparsity for a given number of sensors. The result of this investigation is the third contribution of this thesis in the form of a new sparse array, displaced thinned coprime array with additional sensor (DiTCAAS), which is based on a displaced version of TCA. The displacement of the subarrays generates an increase in the unique lags but the minimum spacing between the sensors becomes an integer multiple of half wavelength. To avoid spatial aliasing, an additional sensor is added at half wavelength from one of the sensors of the displaced subarray. The proposed placement of the additional sensor generates significantly higher number of unique lags for DiTCAAS, even more than the DOFs provided by MRA. Due to its improved sparsity and higher number of unique lags, DiTCAAS generates the lowest estimation error and robustness against heavy mutual coupling compared to super nested arrays, MRA, TCA and sparse CADiS with CS-based DOA estimation.
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Manninen, O. (Olli). "Modelling the antenna arrays using MATLAB-application Sensor Array Analyzer." Bachelor's thesis, University of Oulu, 2017. http://urn.fi/URN:NBN:fi:oulu-201705302196.
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In this thesis, the antenna arrays researched and modelled using Sensor Array Analyzer- application (SAA) from MATLAB. The objective is to explore the array modelling capabilities of the SAA application. This thesis shows that SAA is versatile software for modelling the radiation patterns using 2D or 3D plots, but there are couple of missing features. SAA allows user to import the used code to MATLAB for code modification. Data imported from MATLAB to SAA using variables, for example importing dipole, antenna locations for conformal array and complex coefficients for beamforming. Antenna array wideband usage at SAA discussed and example shown. At SAA, grating lobes seen at 2D and 3D plots and grating lobe- diagram is also used and explained. SAA has no built-in option for mutual coupling compensation. Other practical method for modelling and compensation of mutual coupling are discussedTässä kandidaatintyössä tutkittiin eri geometrian omaavia antenniryhmiä ja niiden mallinnusta MATLAB-ohjelmiston lisäosan SAA:n (Sensor Array Analyzer) avulla. Tehtävänä oli tutkia antenniryhmän eri osa-alueiden mallinnuksen mahdollisuuksia ja rajoituksia kyseisellä ohjelmistolla. Tutkimuksen tuloksena todetaan, että SAA on monipuolinen ohjelmisto antenniryhmien säteilykuvioiden graafiseen havainnollistamiseen 2D- tai 3D-muodossa, vaikkakin muutama perusominaisuus puuttui. Työssä tutkittiin, miten SAA-ohjelmistosta voidaan siirtää käytetty koodi MATLAB-ohjelmistoon sen mahdollista lisämuokkausta varten ja kuinka MATLAB-ohjelmistosta tuodaan tietoa SAA-ohjelmistoon erilaisina muuttujina. Muuttujia tarvitaan esimerkiksi, kun ohjelmistoon tuodaan antennin säteilykuvio, tai sovellettu antenniryhmä sekä niiden kompleksiset kertoimet keilanmuodostusta varten. Laajakaistaisten antenniryhmien säteilykuvion mallinnusta testattiin ja havainnollistettiin. Sivukeiloja, joilla on sama teho pääkeilan kanssa, tarkasteltiin ja niiden havainnollistamiseen luotua diagrammia testattiin. Antennien välisen keskinäiskytkennän mallintamisen mahdollisuuksia tarkasteltiin ja sen vaikutusta säteilykuvioon pohdittiin. Tämän työn tarkoituksena oli selvittää SAA-ohjelmiston pääpiirteiset ominaisuudet ja heikkoudet. Kyseistä tietoa käytetään antenniryhmien keilasynteesiä tutkiessa. Antenniryhmiä voi mallintaa huomattavasti nopeammin ja helpommin käyttämällä SAA-ohjelmistoa, kuin kirjoittamalla itse MATLAB-koodi tai simuloimalla antenniryhmän sähkömagneettinen 3D-malli. Ohjelmiston heikkoudetkin voidaan välttää muokkaamalla koodia haluamalla tavalla. Antenniryhmiä tullaan tulevaisuudessa hyödyntämään IoT-laitteissa ja langattomassa 5G teknologiassa
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Beavington, Richard. "Porphyrin arrays." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388909.
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Promarak, Vinich. "Porphyrin arrays." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249614.
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Zhang, Wei. "Porphyrin arrays." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494395.
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Hughes, Jeff A. "Impedance properties of cylindrical arrays and finite planar arrays." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345482007.
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Khan, Asim Ali. "Performance optimisation of small antenna arrays." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/performance-optimisation-of-small-antenna-arrays(759e6929-04ab-408c-aee3-404c72711cdb).html.
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This thesis addresses radiation pattern synthesis problems for small linear periodic phased arrays (with array elements less then 10). Due to the small array size conventional pattern synthesis techniques fail to produce the required results. In the case of practical small arrays, mutual coupling and element pattern asymmetric effect degrade the array radiation performance. The main performance metrics considered in this thesis include side lobe level (SLL), gain, halfpower beamwidth (HPBW) and mainbeam scan direction. The conventional pattern synthesis approaches result in sub optimal gain, SLL and HPBW due to the limited number of elements and the mutual coupling involved. In case of difference pattern synthesis these factors resulted in lower difference pattern slope, degraded SLL and difference peak asymmetry. The sum and difference patterns are used in monopulse arrays and a simplified feed that could produce both patterns with acceptable radiation properties is of interest and has been examined (chapter 5). A conventional technique is applied to small arrays to synthesise a sector beam and there is limited control over the radiation pattern. It is shown that the mutual coupling has significant effect on the array radiation pattern and mitigation is necessary for optimum performance (chapter 6). Furthermore, wideband phased arrays may have a natural limitation of the HPBW in low gain applications and minimisation of the variation becomes important. Also the SLL variations for wideband antenna arrays in the presence of mutual coupling considerably degrade the radiation pattern. The mutual coupling degrades significantly the radiation pattern performance in case of small scanning wideband arrays (chapter 7). It is the primary goal of this thesis to develop an optimisation scheme thatis applied in the above scenarios (chapters 3 & 4). The only degree of freedom assumed is the array excitation. Optimised amplitude and phase for each element in the array are determined by the proposed scheme, concurrently. The deterministic optimisation techniques reported in the literature for the pattern synthesis may involve complicated problem modelling. The heuristic opti-misation techniques generally are computationally expensive. The proposedIntelligent z-space Boundary Condition-Particle Swarm Optimiser (IzBC-PSO)is based on a heuristic algorithm. This scheme can be applied to a wider rangeof problems without significant modifications and requires fewer computationscompared to the competing techniques.In order to verify the performance of IzBC-PSO antenna array measure-ments were performed in the receiving mode only using the online and offlinedigital beamforming setups described in chapter 8. The measurement resultsshow that the proposed scheme may be successfully applied with both onlineand offline digital beamformers for a practical small array (chapter 8).
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Карнаушенко, В. П., and А. В. Бородин. "Field Programmable Counter Arrays Integration with Field Programmable Gates Arrays." Thesis, NURE, MC&FPGA, 2019. https://mcfpga.nure.ua/conf/2019-mcfpga/10-35598-mcfpga-2019-004.
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Field Programmable Counter Arrays (FPCAs) have been recently introduced to close the gap between Field Programmable Gates Arrays (FPGA) and Application Specified Integrated Circuits (ASICs) for arithmetic dominated applications. FPCAs are reconfigurable lattices that can be embedded into FPGAs to efficiently compute the result of multi-operand additions.
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Kucic, Matthew R. "Analog Computing Arrays." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4878.
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Analog Computing Arrays (ACAs) provide a computation system capable of performing a large number of multiply and add operations in an analog form. This system can therefore implement several computation algorithms that are currently realized using Digital Signal Processors (DSPs) who have an analogues accumulate and add functionality. DSPs are generally preferred for signal processing because they provide an environment that permits programmability once fabricated. ACA systems propose to offer similar functionality by providing a programmable and reconfigurable analog system. ACAs inherent parallelism and analog efficiency present several advantages over DSP implementations of the same systems.
The computation power of an ACA system is directly proportional to the number of computing elements used in the system. Array size is limited by the number of computation elements that can be managed in an array. This number is continually growing and as a result, is permitting the realization of signal processing systems such as real-time speech recognition, image processing, and many other matrix like computation systems.
This research provides a systematic process to implement, program, and use the computation elements in large-scale Analog Computing Arrays. This infrastructure facilitates the incorporation of ACA without the current headaches of programming large arrays of analog floating-gates from off-chip, currently using multiple power supplies, expensive FPGA controllers/computers, and custom Printed Circuit Board (PCB) systems. Proof of the flexibility and usefulness of ACAs has been demonstrated by the construction of two systems, an Analog Fourier Transform and a Vector Quantizer.
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LaForge, Laurence E. (Laurence Edward). "Fault tolerant arrays." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74630.
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We investigate the existence and computability of a fault cover for a configuration architecture; that is, a setting of switches that achieves an array despite the presence of faulty elements and broken interconnect. The switches may be stuck open or closed. For a preponderance of architectures these questions are NP-complete. This is not the case with local sparing, a fundamental approach that can, in fact, be applied to any nominal architecture. We give an algorithm that decides and computes a fault cover in time that is subcubic in the size of a locally spared array whose neighboring blocks of h elements each can be connected in any of h x h ways.We measure scaling in terms of the probability of a fault cover (coverage), the fraction of faults we can tolerate (tolerance), and the ratio of the size of the architecture to the size of the nominal array (redundancy). We establish a threshold tolerance to faults such that, for arbitrary coverage less than 1, a local spares fault cover exists. We prove that the stochastic tolerance of a two-dimensional array spared by local blocks is much better than when spares are arranged by rows and columns. As to the latter, we treat two architectures: homogeneous and dedicated spares, the worst-case tolerance of which is much better than that of local spares. The fault tolerance of each of these architectures is inferior to the general grid scheme of (Leighton and Leiserson 1985). However, the longest wire in an array configured from a general grid is almost never shorter than that of an array configured by local spares.
Although it is not the most tolerant configuration architecture, the combined test and configuration tolerance of local spares is essentially the same as the configuration tolerance alone. Moreover, the stochastic test redundancy of local spares matches the lower bound of (Scheinerman 1987) and (Blough 1988).
We show that convergent hypergeometric and binomial distributions of faults do not imply convergent coverage. We characterize homogeneous spares whose complementary external graph consists of a vertex-disjoint packing of star graphs; this solves exactly a subset of the problem of Zarankiewicz.
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Kennedy, Stephanie Michelle. "Imaging cell arrays." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539580.
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Dohler, Michael. "Virtual antenna arrays." Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407331.
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Amin, H. "Investigations into the hardware implementation of artificial neural networks." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263389.
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Eng, Cher Shin. "Digital antenna architectures using commercial off-the-shelf hardware." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FEng.pdf.
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Thesis (M.S. in Engineering Science (Electrical Engineering)--Naval Postgraduate School, December 2003.Thesis advisor(s): David C. Jenn, Roberto Cristi. Includes bibliographical references (p. 75-76). Also available online.
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Hall, Tyson Stuart. "Field-Programmable Analog Arrays: A Floating-Gate Approach." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07122004-124607/unrestricted/hall%5Ftyson%5Fs%5F200407%5Fphd.pdf.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2005. Directed by David Anderson.Prvulovic, Milos, Committee Member ; Citrin, David, Committee Member ; Lanterman, Aaron, Committee Member ; Yalamanchili, Sudhakar, Committee Member ; Hasler, Paul, Committee Member ; Anderson, David, Committee Chair. Includes bibliographical references.
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Yasar, Temel Kaya. "Improvements In Doa Estimation By Array Interpolation In Non-uniform Linear Arrays." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607524/index.pdf.
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In this thesis a new approach is proposed for non-uniform linear arrays (NLA) which employs conventional subspace methods to improve the direction of arrival (DOA) estimation performance.
Uniform linear arrays (ULA) are composed of evenly spaced sensor elements located on a straight line. ULA's covariance matrix have a Vandermonde matrix structure, which is required by fast subspace DOA estimation algorithms. NLA differ from ULA only by some missing sensor elements. These missing elements cause some gaps in covariance matrix and Vandermonde structure is lost. Therefore fast subspace DOA algorithms can not be applied in this case. Linear programming methods and array interpolation methods can be used to solve this problem. However linear programming is computationally expensive and array interpolation is angular sector dependent and requires the same number of sensor in the virtual array. In this thesis, a covariance matrix augmentation method is developed by using the array interpolation technique and initial DOA estimates. An initial DOA estimate is obtained by Toeplitz completion of the covariance matrix. This initial DOA estimates eliminates the sector dependency and reduces the least square mapping error of array interpolation. A Wiener formulation is developed which allows more sensors in the virtual array than the real array. In addition, it leads to better estimates at low SNR. The new covariance matrix is used in the root-MUSIC algorithm to obtain a better DOA estimate. Several computer simulations are done and it is shown that the proposed approach improves the DOA estimation accuracy significantly compared to the same number of sensor ULA. This approach also increases the number of sources that can be identifed.
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Akyildiz, Isin. "Drection Of Arrival Estimation By Array Interpolation In Randomly Distributed Sensor Arrays." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607963/index.pdf.
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In this thesis, DOA estimation using array interpolation in randomly distributed sensor arrays is considered. Array interpolation is a technique in which a virtual array is obtained from the real array and the outputs of the virtual array, computed from the real array using a linear transformation, is used for direction of arrival estimation. The idea of array interpolation techniques is to make simplified and computationally less demanding high resolution
direction finding methods applicable to the general class of
non-structured arrays.In this study,we apply an interpolation
technique for arbitrary array geometries in an attempt to extend root-MUSIC algorithm to arbitrary array geometries.Another issue of array interpolation related to direction finding is spatial smoothing in the presence of multipath sources.It is shown that due to the Vandermonde structure of virtual array manifold vector obtained from the proposed interpolation method, it is possible to use spatial smoothing algorithms for the case of multipath sources.
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Abhayapala, P. Thushara D., and Thushara Abhayapala@anu edu au. "Modal Analysis and Synthesis of Broadband Nearfield Beamforming Arrays." The Australian National University. Telecommunications Engineering Group, 2000. http://thesis.anu.edu.au./public/adt-ANU20010905.121231.
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This thesis considers the design of a beamformer which can enhance desired signals in an environment consisting of broadband nearfield and/or farfield sources. The thesis contains: a formulation of a set of analysis tools which can provide insight into the intrinsic structure of array processing problems; a methodology for nearfield beamforming; theory and design of a general broadband beamformer; and a consideration of a coherent nearfield broadband adaptive beamforming problem. To a lesser extent, the source localization problem and background noise modeling are also treated.
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A set of analysis tools called modal analysis techniques which can be used to a solve wider class of array signal processing problems, is first formulated. The solution to the classical wave equation is studied in detail and exploited in order to develop these techniques.
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Three novel methods of designing a beamformer having a desired nearfield broadband beampattern are presented. The first method uses the modal analysis techniques to transform the desired nearfield beampattern to an equivalent farfield beampattern. A farfield beamformer is then designed for a transformed farfield beampattern which, if achieved, gives the desired nearfield pattern exactly. The second method establishes an asymptotic equivalence, up to complex conjugation, of two problems: (i) determining the nearfield performance of a farfield beampattern specification, and (ii) determining the equivalent farfield beampattern corresponding to a nearfield beampattern specification. Using this reciprocity relationship a computationally simple nearfield beamforming procedure is developed. The third method uses the modal analysis techniques to find a linear transformation between the array weights required to have the desired beampattern for farfield and nearfield, respectively.
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An efficient parameterization for the general broadband beamforming problem is introduced with a single parameter to focus the beamformer to a desired operating radius and another set of parameters to control the actual broadband beampattern shape. This parameterization is derived using the modal analysis techniques and the concept of the theoretical continuous aperture.
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A design of an adaptive beamformer to operate in a signal environment consisting of broadband nearfield sources, where some of interfering signals may be correlated with desired signal is also considered. Application of modal analysis techniques to noise modeling and broadband coherent source localization conclude the thesis.
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Bronk, Karen Srour. "Imaging based sensor arrays /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1996.
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Thesis (Ph.D.)--Tufts University, 1996.Adviser: David R. Walt. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Raaphorst, Sebastian. "Variable Strength Covering Arrays." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23684.
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Recently, covering arrays have been the subject of considerable research attention as they hold both theoretical interest and practical importance due to their applications to testing. In this thesis, we perform the first comprehensive study of a generalization of covering arrays called variable strength covering arrays, where we dictate the interactions to be covered in the array by modeling them as facets of an abstract simplicial complex.
We outline the necessary background in the theory of hypergraphs, combinatorial testing, and design theory that is relevant to the study of variable strength covering arrays. We then approach questions that arise in variable strength covering arrays in a number of ways. We demonstrate their connections to hypergraph homomorphisms, and explore the properties of a particular family of abstract simplicial complexes, the qualitative independence hypergraphs. These hypergraphs are tightly linked to variable strength covering arrays, and we determine and identify several of their important properties and subhypergraphs.
We give a detailed study of constructions for variable strength covering arrays, and provide several operations and divide-and-conquer techniques that can be used in building them. In addition, we give a construction using linear feedback shift registers from primitive polynomials of degree 3 over arbitrary finite fields to find variable strength covering arrays, which we extend to strength-3 covering arrays whose sizes are smaller than many of the best known sizes of covering arrays.
We then give an algorithm for creating variable strength covering arrays over arbitrary abstract simplicial complexes, which builds the arrays one row at a time, using a density concept to guarantee that the size of the resultant array is asymptotic in the logarithm of the number of facets in the abstact simplicial complex. This algorithm is of immediate practical importance, as it can be used to create test suites for combinatorial testing.
Finally, we use the Lovasz Local Lemma to nonconstructively determine upper bounds on the sizes of arrays for a number of different families of hypergraphs. We lay out a framework that can be used for many hypergraphs, and then discuss possible strategies that can be taken in asymmetric problems.
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MacNair, David Luke. "Modeling cellular actuator arrays." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50259.
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This work explores the representations and mathematical modeling of biologically-inspired robotic muscles called Cellular Actuator Arrays. These actuator arrays are made of many small interconnected actuation units which work together to provide force, displacement, robustness and other properties beyond the original actuator's capability. The arrays can also exhibit properties generally associated with biological muscle and can thus provide test bed for research into the interrelated nature of the nervous system and muscles, kinematics/dynamics experiments to understand balance and synergies, and building full-strength, safe muscles for prosthesis, rehabilitation, human force amplification, and humanoid robotics.
This thesis focuses on the mathematical tools needed bridge the gap between the conceptual idea of the cellular actuator array and the engineering design processes needed to build physical robotic muscles. The work explores the representation and notation needed to express complex actuator array typologies, the mathematical modeling needed to represent the complex dynamics of the arrays, and properties to guide the selection of arrays for engineering purposes. The approach is designed to aid automation and simulation of actuator arrays and provide an intuitive base for future controls and physiology work. The work is validated through numerical results using MatLab's SimMechanics dynamic modeling system and with three physical actuator arrays built using solenoids and shape memory alloy actuators.
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Nobakhti, Abbas. "Articulations in floating arrays." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251819.
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Hong, Ching-yin 1973. "Intelligent field emission arrays." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17037.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.Includes bibliographical references (p. 289-301).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Field emission arrays (FEAs) have been studied extensively as potential electron sources for a number of vacuum microelectronic device applications. For most applications, temporal current stability and spatial current uniformity are major concerns. Using the kinetic model of electron emission, field emission can be described as two sequential processes- the flux of electrons to the tip surface followed by the transmission of the electrons through the surface barrier. Either of these processes could be the determinant of the emission current. Unstable emission current is usually due to absorption/desorption of gas molecules on the tip surface (barrier height variation) and non-uniform emission is usually due to tip radius variation (barrier width change). These problems could be solved if the emission current is determined by the electron supply to the surface instead of the electron transmission through the surface barrier. In this thesis, we used the inversion layer of a MOSFET to control the electron supply. It results in additional benefits of low turn-on voltage and low voltage swing to turn the device on and off. A novel CMP-based process for fabricating integrated LD-MOSFET/FEA is presented. We obtained FEA devices with an extraction gate aperture of 1.3 [mu]m and emitter height of 1 [mu]m. We present a comprehensive study of field emitter arrays with or without MOSFET. The silicon field emitter shows turn-on voltage of [approximately]24 V with field enhancement factor (b[sub]FN) of [approximately]370. We demonstrated that the LD-MOSFET provides excellent control of emission current. The threshold voltage of the LD-MOSFET is [approximately]0.5V. The integrated device can be switched ON and OFF using a MOSFET gate voltage swing of 0.5V. This results in an ON/OFF current ratio of 1000:1. The current fluctuation is significantly reduced when the MOSFET is integrated with the FEA device and the device is operated in the MOSFET control regime. The emission current of the integrated LD-MOSFET/FEA remains stable regardless the gas and vacuum condition. The saturation current level of the integrated devices in the MOSFET controlled region is also the same regardless the emitter array size or the FEA's position on the wafer. We also present a comprehensive study of three-dimensional oxidation in silicon emitter tip
(cont.) formation. Stress plays an important role in the oxidation mechanism. A new sharp emitter tip formation mechanism is proposed: rather than a continuous oxidation process, an emitter neck breaking stage occurs before the sharp emitter tip is formed. Stress from volume difference of silicon and silicon dioxide is the main cause for the emitter neck breaking. Initial formation of microcracks around the neck occurs at high temperature due to volume difference stress, oxide grows into the cracks right after crack formation, and a sharp emitter tip is then formed by further oxidation.
by Ching-yin Hong.
Ph.D.
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Darling, Scott Lee. "Multiporphyrin and multimetallic arrays." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624436.
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Storey, Jonathan P. "Advanced reconfigurable photovoltaic arrays." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386864/.
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This thesis describes works relating to advancements in the field of dynamic photovoltaic arrays (DPVA). This subject is becoming extremely active with a flurry of new papers appearing in recent times, all detailing ideas and developments regarding a range of engineering issues. One of the biggest problems with any photovoltaic system is the non-linear reduction in power output caused by the partial shading of the array surface. This is the main focal point of the developments discussed where new techniques regarding the reconfiguration of photovoltaic devices within a topology are identified and used to reduce the negative effects of non uniform insolation. In particular, the most successful type of dynamic array has been modified (the Irradiance Equalized Dynamic Photovoltaic Array) such that it now exhibits it's maximum flexibility and is able to show complete resilience to partial shading allowing for maximum power extraction. Furthermore, the operational speed of the device has been increased so that it can operate in real time with minimal computational effort and we have investigated the future of the device as source of electricity in a wide range of applications. On top of that, a second completely new type of dynamic array (the Optimise String Dynamic Photovoltaic Array) that demonstrates unique behaviour is presented and tested via a custom made simulator programmed into MATLAB. Both of these developments have included conceiving new sorting algorithms that are particularly rapid in their execution while obtaining a high level of optimisation. Three other classes of arrays found in literature are discussed and their characteristics are identified while concerns with their implementation are cross is examined. A new classification framework used in identifying all types of dynamic array has been introduced. This is very useful when discussing the main attributes associated with the various contributions made by authors of the literature. Not only this but it also allows for a comparative study between matrix architecture and device flexibility for arrays within the same class. A simulator that uses standard mathematical models to virtually realise irradiated solar cells and then perform the operations dictated by the sorting algorithms is presented. It reveals in detail the behaviour of featured DPVAs under a complete range of environments. Working with that, a new comprehensive test procedure has been developed that exercises the simulated arrays and documents their expected output under precisely controlled conditions. The resulting graphs are extremely useful in highlighting to the researcher the proficiency's and failings of the arrays under said conditions. This simulation environment interfaces to a real 16 section prototype array so that predictions can be verified by experimentation. The device can be used in such a way that it mimics the simulated dynamic array, while also providing a convenient terminal where more bespoke tests can be conducted. As will be discussed, all market bound DPVA research must be conducted with both a virtual and physical devices because each environment provides an incite that is of great importance to the designer. A later discussion introduces some abstract but potentially significant ideas about synthesising AC electricity using the switching mechanism. An argument suggesting why an industrially accepted synthesis method is not suitable for photovoltaic use is given and a more suitable solution is hypothesized. To finish there is a discussion about the remaining unexplored topics in the field which highlights how and why further research is required. The aim of this is to acknowledge that more work is needed but also to show the way to developing a completely new state of the art source of electricity which may one day help society effectively exploit the abundance of power being delivered to us by the Sun.
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Gillett, Philip Winslow. "Head Mounted Microphone Arrays." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28867.
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Microphone arrays are becoming increasingly integrated into every facet of life. From sonar to gunshot detection systems to hearing aids, the performance of each system is enhanced when multi-sensor processing is implemented in lieu of single sensor processing. Head mounted microphone arrays have a broad spectrum of uses that follow the rigorous demands of human hearing. From noise cancellation to focused listening, from localization to classification of sound sources, any and all attributes of human hearing may be augmented through the use of microphone arrays and signal processing algorithms. Placing a set of headphones on a human provides several desirable features such as hearing protection, control over the acoustic environment (via headphone speakers), and a means of communication. The shortcoming of headphones is the complete occlusion of the pinnae (the ears), disrupting auditory cues utilized by humans for sound localization.
This thesis presents the underlying theory in designing microphone arrays placed on diffracting bodies, specifically the human head. A progression from simple to complex geometries chronicles the effect of diffracting structures on array manifold matrices. Experimental results validate theoretical and computational models showing that arrays mounted on diffracting structures provide better beamforming and localization performance than arrays mounted in the free field. Data independent, statistically optimal, and adaptive beamforming methods are presented to cover a broad range of goals present in array applications. A framework is developed to determine the performance potential of microphone array designs regardless of geometric complexity. Directivity index, white noise gain, and singular value decomposition are all utilized as performance metrics for array comparisons. The biological basis for human hearing is presented as a fundamental attribute of headset array optimization methods. A method for optimizing microphone locations for the purpose of the recreation of HRTFs is presented, allowing transparent hearing (also called natural hearing restoration) to be performed. Results of psychoacoustic testing with a prototype headset array are presented and examined. Subjective testing shows statistically significant improvements over occluded localization when equipped with this new transparent hearing system prototype.Ph. D.
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Tong, Yizhen. "Time modulated linear arrays." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4859/.
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With increasing demand for modern technology in the communication systems, antenna arrays have attracted much interest in the areas of radio broadcasting, space communication, weather forecasting, radar and imaging. Antenna array with controlled low or ultralow sidelobes is of particular importance and it has been an on-going challenge for the antenna design engineers in the past few decades, as it requires a high dynamic range of excitations. Another desired feature provided by an antenna array is the ability to perform electronic beam steering and adaptive interference suppression. These benefits can be achieved with the use of complicated feed network and expensive phase shifters and it can only found in the specialised military systems. Therefore this has motivated the research into the development of a simple and low cost system for the commercial applications. The idea of time modulation was proposed to produce an antenna pattern with controlled low or ultralow sidelobe level, as well as achieving real time electronic beam scanning without the use of phase shifter. However, a fundamental problem of this concept is the generation of undesired harmonics or sidebands as they waste power. This dissertation mainly focuses on the two important characteristics - pattern synthesis and multiple beams scanning of the time modulated antenna array and evaluates its potential application in the communication system. The first main chapter of this research proposes two novel approaches to successfully suppress the sideband radiation and hence improve radiation efficiency. The following part of the study introduces a way of combining the electronic beam scanning with the controlled low or ultralow sidelobes and applies the null steering technique in the time modulated linear array. The final but most important attribute of this thesis is to propose the concept of time redundancy and evaluate the potential feasibility of employing smart antenna technology into the time modulated antenna array for a two-channel communication system, where individual adaptive beamforming can be performed to extract desired signal while suppressing interference from separate sources independently.
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Wang, Yang. "Time-modulated reflector-arrays." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8510/.
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This PhD thesis introduces the time-modulated reflector-arrays which are a hybrid of conventional time-modulated array (TMA) systems and reflectarrays. The TMRAs use a similar layout of reflectarray feed by a source. Compared to conventional phased arrays, reflectarrays and time-modulated arrays, a TMRA is potentially simpler to implement in hardware as it does not need a complicated feeding network or the use of the phase shifting units. Instead of phase shifting units, TMRAs use discrete time-switching to achieve beamforming functions. The concept and operating mechanism of the TMRA is explained using a simple model based on isotropic scatterers. A more sophisticated TMRA based on an 8 element array of PIN-diode controlled bow-tie dipole elements is designed and analysed using a full-wave commercial simulator. A hardware implementation of the bowtie dipole TMRA system, including control circuitry, is also described and measured data is presented. The simulated and measured results confirm that the time-modulated reflector array system performs the required function of harmonic beam steering. Moreover, TMRAs can provide functions such as sidelobe suppression and adaptive beamforming. The thesis also provide solutions to the challenges of TMRAs such as low system efficiency and phases variances caused by feeding paths. Overall TMRAs combine the benefits of conventional TMA systems and reflectarrays. They can provide similar functions of conventional TMAs, phased arrays and reflectarrays without the need of expensive phase shifters and lossy transmission lines. This makes TMRAs a very good candidates in applications over millimetre-wavelength frequency band.
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Livadaru, Matilda Gabriela. "Low Cost Scanning Arrays." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3780.
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Over the past decades, phased arrays have played a significant role in the development of modern radar and communication systems. The availability of printed circuit technology and ease of integration with microwave components, as well as the development of low profile and low weight approaches, have also played an important role in their conformal adaptation. However, fabrication costs remain prohibitive for many emergent platforms, including 5G base stations and autonomous vehicles, when compared to a conventional mechanically steered passive array. Therefore, cost reductions in the fabrication and integration of modern phased arrays are essential to their adaptation for many upcoming commercial applications. Indeed, although phased array design methods are well-understood, even for wideband and wide-angle scanning applications, their fabrication is still based on high-cost, low-yield printed circuit technology. With this in mind, this dissertation focuses on a new planar aperture topology and low-cost techniques for phased array methodologies.
The first part of the thesis presents new fabrication advancements using commercially available multi-layered printed circuit technologies. We discuss methods for low cost fabrication while still maintaining performance and design constraints for planar array apertures. The second part of the dissertation presents a novel Integrated Planar Array (IPA) at S-Band and discusses dramatic cost reductions for multi-function radar applications. Performance and cost benefits are presented, and fabrication techniques to exploit an emerging class of high-speed digital laminates are discussed. These are compatible with high-volume, high-yield production, while reducing aperture cost by 75% when compared to conventional approaches.
Performance of a planar array employing a pin-fed dual-polarized antenna element with active VSWR
Overall, this dissertation addresses several manufacturing and performance challenges in realizing affordable planar phased arrays using low cost fabrication without performance compromise. As commercial interest in phased array technology is anticipated to grow, the proposed approaches for phased array design and fabrication will enable quick turnaround times for mainstream adoption.
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Yang, Zhenchao. "High-Efficiency Passive and Active Phased Arrays and Array Feeds for Satellite Communications." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5741.
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Satellite communication (Satcom) services are used worldwide for voice, data, and video links due to various appealing features. Parabolic reflector antennas are typically used to serve a cost effective scheme for commercial applications. However, mount degradation, roof sag, and orbital decay motivate the need for beam steering. Limited scan range beam steering opens a third option for electronic beam steering with lower cost than full aperture phased arrays and higher tracking speed and accuracy than mechanical-only steering.Multiple high efficiency passive patch array feeds were designed, fabricated, and measured, including a 2x2 MSA array, a stacked shorted annular patch antenna, and an SIW-fed hexagonal array feed based on PTFE material, achieving performance comparable to a horn feed. For multiband dual polarization applications, passive MSA feed solutions are also provided. Multiple MSA array feeds with high isolation were designed for dual band dual polarization applications. More functionality can be realized with multi-layer PCB techniques for complex communication scenarios.Limited scan range electronic beam-steering with a parabolic reflector fed by an active array feed which only needs gain control was demonstrated experimentally, leading to a low cost and effective solution for active beam scanning. A cost-effective flat-panel phased array with limited scan range electronic beam-steering was proposed by tiling high efficiency 4x4 passive subarrays and performing beam scanning at the tile level. The sidelobe issue was also investigated to comply with the pattern mask requirement set by FCC.To enable better use of circularly polarized (CP) MSAs for electronically beam-formed antenna systems, the impact of mutual coupling on the performance of high-sensitivity dual-polarized receivers for satellite communications applications was analyzed. A new analysis method for intrinsically dual-CP MSAs based on an equivalent circuit model and Jones matrices was proposed and validated to overcome the port isolation challenge. The model provides accurate estimates of impedances and S-parameters, as well as field parameters such as axial ratio. The feasible region for XPI and impedance mismatch factor is found for dual CP antennas. The circuit model enables multiple useful applications. Effective decoupling and matching schemes was proposed and demonstrated, leading to a high isolation, good match, and wide AR bandwidth dual CP MSA for satellite communications.
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Malik, Usama Computer Science & Engineering Faculty of Engineering UNSW. "Configuration encoding techniques for fast FPGA reconfiguration." Awarded by:University of New South Wales. School of Computer Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/26212.
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This thesis examines the problem of reducing reconfiguration time of an island-style FPGA at its configuration memory level. The approach followed is to examine configuration encoding techniques in order to reduce the size of the bitstream that must be loaded onto the device to perform a reconfiguration. A detailed analysis of a set of benchmark circuits on various island-style FPGAs shows that a typical circuit randomly changes a small number of bits in the {\it null} or default configuration state of the device. This feature is exploited by developing efficient encoding schemes for configuration data. For a wide set of benchmark circuits on various FPGAs, it is shown that the proposed methods outperform all previous configuration compression methods and, depending upon the relative size of the circuit to the device, compress within 5\% of the fundamental information theoretic limit. Moreover, it is shown that the corresponding decoders are simple to implement in hardware and scale well with device size and available configuration bandwidth. It is not unreasonable to expect that with little modification to existing FPGA configuration memory systems and acceptable increase in configuration power a 10-fold improvement in configuration delay could be achieved. The main contribution of this thesis is that it defines the limit of configuration compression for the FPGAs under consideration and develops practical methods of overcoming this reconfiguration bottleneck. The functional density of reconfigurable devices could thereby be enhanced and the range of potential applications reasonably expanded.
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Koh, Shannon Computer Science & Engineering Faculty of Engineering UNSW. "Generating the communication infrastracture for module-based dynamic reconfiguration of FPGas." Publisher:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41418.
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Current approaches to supporting module-based FPGA reconfiguration focus on various aspects and sub-problems in the area but do not combine to form a coherent, top-down methodology that factors low-level device parameters into every step of the design flow. This thesis proposes such a top-down methodology from application specification to low-level implementation, centered around examining the problem of generating a point-to-point communications infrastructure to support the changing interfaces of dynamically placed modules. Low-level implementation parameters are considered at every stage to ensure that area, timing and budget constraints of the application are met. The approach advocates the regular layout of modules surrounded by a wiring harness supporting the communications for those modules, and thus provides an advanced understanding of how to implement the "fixed wiring harness" model of reconfigurable computing proposed by Brebner. Results have shown that compared to flattened net lists the regularity of the layout does not impose significant overheads on critical path delays. At high communication densities it can even result in lower delays. The core of the methodology is an infrastructure generation process that allocates modules to slots and merges configuration graphs to form wiring harnesses that support the communications for these merged configurations. This thesis suggests methods and evaluates algorithms for configuration graph merging so as to reduce run-time reconfiguration overheads. Initial experiments with a greedy merging algorithm performed on an optical flow application resulted in a substantial reduction of 64% in reconfiguration time. The effects of graph merging with the initial greedy algorithm and an improved dynamic programming algorithm were explored for a range of device sizes and architectural parameters. Results show that configuration merging using the greedy method results in significant reductions to the reconfiguration delay. The dynamic programming algorithm provides consistent improvements above and beyond the savings provided by the greedy method. In addition, a strong correlation was identified between the quality of front-end design activities such as partitioning and the effectiveness of back-end implementations. The methodology is integrated into the Xilinx commercial tool flow for partial reconfiguration, and is effective for implementing applications for module-based FPGA reconfiguration where the modules and their communications requirements are known at design time. It also allows a system designer to consider alternate device sizes and parameters until a set is found that satisfies the application constraints.
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Schodorf, Jeffrey Brian. "Array processing techniques for interference suppression in mobile communications systems." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12971.
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Wood, Christopher Landon. "Runtime partial FPGA reconfiguration." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15051.
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Galindo, Juan Manuel. "A novel partial reconfiguration methodology for FPGAs of multichip systems /." Online version of thesis, 2008. http://hdl.handle.net/1850/7784.
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Rajagopalan, Kamal. "An FPGA architecture for improved arithmetic performance /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16460.pdf.
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Han, Yi. "Development of nonlinear reconfigurable control of reconfigurable plants using the FPGA technology." Thesis, [S.l. : s.n.], 2008. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1011&context=td_cput.
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Cassels, Joshua, and Anant Godbole. "Covering Arrays for Equivalence Classes of Words." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/honors/446.
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Covering arrays for words of length t over a d letter alphabet are k × n arrays with entries from the alphabet so that for each choice of t columns, each of the dt t-letter words appears at least once among the rows of the selected columns. We study two schemes in which all words are not considered to be different. In the first case, words are equivalent if they induce the same partition of a t element set. In the second case, words of the same weighted sum are equivalent. In both cases we produce logarithmic upper bounds on the minimum size k = k(n) of a covering array. Most definitive results are for t = 2, 3, 4.
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Buxton, Carey G. "Design of a Broadband Array Using the Foursquare Radiating Element." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28363.
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Broadband scanning arrays require small element spacing over a broad frequency band to achieve the desired scan capabilities. Previous research has concentrated on the development of small broadband elements to meet the demands of broadband arrays. However, mutual coupling between elements in a tightly spaced array can change the operating frequency and bandwidth from that of the single isolated element. Several research efforts have focused on minimizing the mutual coupling to maintain the frequency response of the single isolated element. This dissertation focuses on using the strong coupling between Foursquare antennas to obtain the broadband frequency response while maintaining a small element spacing.
The isolated Foursquare antenna was modeled using an in-house FDTD code. The modeled current distribution over the frequency band of operation revealed how the antenna achieved a broadband frequency response. Because of this understanding of the single element, the downward shift in the frequency response of the Foursquare antenna in a fully active array could be anticipated. Furthermore, the infinite array models of the Foursquare revealed an increase in bandwidth. Both are desirable characteristics for a broadband scanning array. Therefore, through this research using the Foursquare element, it has been shown that the strong mutual coupling in a tightly spaced array can have advantages if initially taken into consideration when designing the array.Ph. D.
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Kumar, Sharath. "Investigation of a Phased Array of Circular Microstrip Patch Elements Conformal to a Paraboloidal Surface." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/35464.
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This thesis investigates the performance of a phased array of antenna elements conforming to a paraboloidal surface. We hypothesize that such a conformal phased array would have performance comparable to that of a correspondingly sized planar array. The performance of a paraboloidal array of antenna elements was simulated using an array program, and the resulting gains, side-lobe levels, and half-power beamwidths compared to those of a similarly sized planar array. Furthermore, we propose a beam-forming feed network for this paraboloidal phased array, and discuss the influence that coupling between the elements could have on the array performance. Lastly, we propose that such an array be used in conjunction with a parabolic reflector antenna to form a versatile hybrid antenna with several potential applications.Master of Science
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Sharma, Akshay. "Place and route techniques for FPGA architecture advancement /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6108.
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Young, W. F. "Optimizing arrays of randomly placed wireless transmitters with receivers located in the array volume." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239401.
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Ng, Kwong-Tai. "Admittance properties of a slot array with parasitic wire arrays in a stratified medium /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259580262744.
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Abewardana, Wijenayake Chamith K. "Multi-dimensional Signal Processing And Circuits For Advanced Electronically Scanned Antenna Arrays." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415358304.
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Klein, Andreas. "Generalisierte Berechnungen in iterativen Arrays." [S.l. : s.n.], 1999. http://bibd.uni-giessen.de/gdoc/2000/uni/d000003.ps.
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