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- Universidade Federal do Rio Grande do Sul
- Monterey, California. Naval Postgraduate School
- Monterey California. Naval Postgraduate School
- Monterey, California: Naval Postgraduate School
- The United States of America as represented by the Secretary of the Navy, Washington, DC (US)
- Escola de Pós-Graduação Naval
- Biblioteca Digital da Unicamp
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## Diagrama de fases e anomalia na densidade em modelo de gás de rede associativo

Fonte: Universidade Federal do Rio Grande do Sul
Publicador: Universidade Federal do Rio Grande do Sul

Tipo: Tese de Doutorado
Formato: application/pdf

Português

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Neste trabalho exploramos um modelo de gás de rede em uma rede triangular em duas dimensões que apresenta dois tipos de interações: interação de curto alcance e interação tipo ligações de hidrogênio. Exploramos o modelo com o intuito de verificar se um sistema com interações de duas escalas apresenta anomalia na densidade. Em primeiro lugar, analisamos o comportamento do sistema com ligações de hidrogênio opostas e simétricas frente a mudanças de temperatura e potencial químico. Mostramos que o sistema apresenta as seguintes fases: gás, liquido de baixa densidade, líquido de alta densidade e fluido. Além disso, o sistema tem uma região de pressão onde, à pressão constante, a densidade apresenta um máximo. Em segundo lugar, analisamos os efeitos no diagrama de fases de potencial químico versus temperatura, da inclusão de estados com distorções nas ligações de hidrogênio. Encontramos que as distorções mantém as fases gás, líquido de baixa densidade, líquido de alta densidade e a anomalia na densidade. As distorções, no entanto, levam as fronteiras de fase e a anomalia para temperaturas mais baixas em decorrência do aumento da entropia devido ao acréscimo no número de estados de ligações de hidrogênio. Tanto o modelo com ligações rígidas quanto o modelo proposto com distorções foram estudados por métodos de simulação de Monte Carlo...

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## A virtual RSNS direction finding antenna system

Fonte: Monterey, California. Naval Postgraduate School
Publicador: Monterey, California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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Approved for public release; distribution in unlimited.; In this thesis, a performance analysis and improvement of a phase sampling interferometer antenna system based on the Robust Symmetrical Number System (RSNS) in the presence of noise is investigated. Previous works have shown that the RSNS-based DF technique can provide high bearing resolution with a minimum number of antenna elements. However, the previous experimental data showed significant deviation from the theoretical results expected due to imperfections, errors, and noise. Therefore, an additive Gaussian noise model of RSNS-based DF was established and simulated. Simulation results show that the presence of noise distorts the signal amplitudes used in the RSNS processor and causes degradation of the angle-ofarrival estimates. A performance analysis was undertaken by first introducing the quadrature modulation configuration into RSNS-based DF system, which provided a digital antenna approach for more flexibility in the signal processing. With a digital approach, variable resolution signal preprocessing can be employed, using a virtual channel concept. The virtual channel concept changes moduli values without changing the actual physical antenna element spacing. This attractive property allows the RSNS algorithm to be implemented into existing antenna arrays and only requires modifying the antenna signal processor. Computer simulation results showed that the proposed method can successfully improve the system performance and also mitigate the effects of noise.

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## Symmetrical residue-to-binary conversion algorithm, pipelined FPGA implementation, and testing logic for use in high-speed folding digitizers

Fonte: Monterey, California. Naval Postgraduate School
Publicador: Monterey, California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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The robust symmetrical number system (RSNS) can play a significant role in the reduction of encoding errors within a low-power folding analog-to-digital converter (ADC). A key part of this ADC design is the logic block that converts the symmetrical residues from each channel into a more convenient binary output. This thesis describes a robust symmetrical residue-to-binary conversion algorithm for moduli 1 7 m =, 2 8 m = and 3 9 m = (ADC dynamic range M = 126). Also described is a pipelined digital logic implementation for use in high speed programmable logic or application specific integrated circuits. To verify correct outputs of the robust symmetrical residue-to-binary conversion algorithm, a digital test circuit is described that generates the thermometer code (symmetrical residues) for the 3-channel ADC design.

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## Photonic analog-to-digital coonversion using a robust symmetrical number system

Fonte: Monterey California. Naval Postgraduate School
Publicador: Monterey California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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A photonic analog-to-digital converter (ADC) based on a robust symmetrical number system (RSNS) was constructed and tested. The analog signal to be converted is used to amplitude modulate an optical pulse from a laser using three Mach-Zehnder interferometers (MZI). The Mach-Zehnder interferometers fold the input analog signal for a three-channel RSNS encoding. The folding waveforms are then detected and amplitude-analyzed by three separate comparator banks, the outputs of which are used to determine a digital representation of the analog signal. This design uses the RSNS preprocessing to encode the signal with the fewest number of comparators for any selected bit resolution. In addition to the efficiency of its use of comparators, the RSNS encoding has inherent Gray-code properties making it particularly attractive for eliminating any possible encoding errors. The RSNS encoding is combined with an optical infrastructure that offers high bandwidth and low insertion loss characteristics. A full implementation was constructed and tested. The lack of a high-speed data acquisition device limited the results to examining the preprocessing and digital processing separately. With the system integration of a data acquisition device, a wideband direct digital antenna architecture can be demonstrated.

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## Variable resolution direction finding using the robust symmetrical number system

Fonte: Monterey, California. Naval Postgraduate School
Publicador: Monterey, California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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A digital implementation of a phase sampling interferometer antenna system based on the Robust Symmetrical Number System (RSNS) is built using commercial-off-the-shelf (COTS) items. The RSNS-based direction finding (DF) system uses short baselines to achieve a high resolution DF capability in a physically compact system for use as stand-in sensors on unmanned aerial vehicles. The RSNS inherent integer Gray code property minimizes the possible encoding errors and adds a robustness to the accuracy of the estimated Angle of Arrival (AOA). A digital architecture using quadrature demodulators and real-time controllers provide grreater flexibility for signal processing and allows for the implementation of a new virtual spacing algorithm. The virtual spacing concept changes the RSNS moduli values to implement a virtual antenna spacing without having to physically change the antenna element spacing. This enables higher resolution DF in circumstances where the Signal-to-Noise Ratio is high enough to provide error free coding of the AOA. Two four element, digital 3-channel interferometer prototype systems were constructed and tested in the NPS anechoic chamber. The first antenna array is designed using pairwise relatively prime (PRP) moduli. When an extension of the virtual spacing concept for application to N-channel systems was successfully resolved...

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## Design and development of a single channel RSNS direction finder

Fonte: Monterey, California: Naval Postgraduate School
Publicador: Monterey, California: Naval Postgraduate School

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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This thesis carried out the design and development of a single channel Robust Symmetrical Number System (RSNS) virtual spacing direction finding (DF) system. This was based on previous work on a three-channel RSNS virtual spacing DF system. Various moduli sets were chosen and run through MATLAB simulations. The results showed unacceptably large errors at low signal-to-noise ratios (SNRs) for all sets. Large dynamic range moduli sets yielded relatively high errors when compared with the small dynamic range moduli sets. The effect of number of channels was studied and found to be mostly inconsequential for similar resolutions. The simulation included phase errors from noise and spacing errors. The virtual single channel concept was integrated into a hardware system. A bench top setup with amplifier and demodulator cards was constructed. This system was connected to two National Instruments (NI) PXI-5112 cards. LabVIEW software was used to calibrate the demodulator cards and to run the RSNS program.

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## FPGA implementation of robust symmetrical number system in high-speed folding analog-to-digital converters

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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Analog-To-Digital Converters (ADCs) are integral building blocks of most sensor and communication systems today. As the need for ADCs with faster conversion speeds and lower power dissipation increases, there is a growing motivation to reduce the number of power-consuming components by employing folding circuits to fold the input analog signal symmetrically prior to quantization by high-speed comparators. These properties of low-power consumption, compactness, high-resolution and fast conversion speeds make folding ADCs an attractive concept to be used for defense applications, such as unmanned systems, direction-finding antenna architectures and system-on-a-chip applications. In this thesis, a prototype of an optical folding ADC was implemented using the Robust Symmetrical Number System (RSNS). The architecture employs a three-modulus (Moduli 7, 8, 9) scheme to preprocess the antenna signal. This thesis focuses on the simulation and hardware implementation of this ADC architecture, including the bank of comparators and the RSNS-to-Binary Conversion within a Field Programmable Gate Array (FPGA), to achieve an eight-bit dynamic range of 133. This is then integrated with the front-end photonics implementation (designed under a separate thesis). Low frequency analyses of the results using a 1-kHz input signal indicate a 5.39 Effective Number of Bits (ENOB)...

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## Extending the dynamic range of a photonic RSNS ADC using a segmentation approach

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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The trend in high-performance digital receivers is to configure the analog-to-digital converter (ADC) directly after the antenna and low noise amplifier. Direct digitization of wideband antenna signals can be realized using Mach-Zehnder interferometers (MZI) to efficiently fold the RF signal into the optical domain. The robust symmetrical number system (RSNS) is a modular scheme formed using N ? 2 integer sequences and insures that any two successive vectors or paired terms from all N sequences differ by only one integer (integer Gray code property). A photonic ADC preprocessing architecture using the RSNS uses a modulus i m number of comparators at the output of each MZI/photodetector. The total number of comparators with a logic ?1? in each channel represents the integer values within each RSNS sequence. The dynamic range

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## Design of a phase sampled interferometry antenna using the robust symmetrical number system

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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This research has examined the benefits of using the Robust Symmetrical Number System (RSNS) to resolve ambiguities in phase sampling interferometry. A compact, high resolution direction finding antenna architecture based on the RSNS was developed to demonstrate experimentally the elimination of phase errors using a minimum amount of hardware. Previous work has determined that phase errors in the system will degrade the system performance. Several improvements were made to the original RSNS prototype antenna to provide enhanced performance. Adding isolators and supplementing the ground plane with copper tape (between the antenna elements), a reduction in the mutual coupling effects was accomplished. Mounting the microwave components on a brass plate also reduced errors contributed by vibrations and temperature. Tailor cutting all semi-rigid coaxial lines also helped reduce the number of connectors required to assemble the microwave circuit, also a source of phase errors. Matching the front-end amplifiers in each amplification stage rather than matching the characteristics of two cascaded amplifiers in each signal line has reduced relative phase errors between channels as well as matching the power outputs of the amplifiers. Two printed circuit boards were designed and built for the RSNS signal processor. The printed circuit boards provide a decrease in the electrical noise floor over the original design (assembled on breadboards). The new design has reduced the phase errors that were present in the first prototype system. The RSNS signal processing technique is able to provide a high-resolution phase sampled direction finding capability with an angular resolution of 1.9 degrees by using only three receiving elements (two interferometers)

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## A Robust Symmetrical Number System with Gray code properties for applications in signal processing

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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Approved for public release; distribution is unlimited; A new symmetrical number system with applications in parallel signal processing is investigated. The Robust Symmetrical Number System (RSNS) is a modular system in which the integer values within each modulus, when considered together, change one at a time at the next position (Gray code properties). Although the observed dynamic range of the RSNS is somewhat less than the optimum symmetrical number system, the Gray code properties make it particularly attractive for folding analog-to-digital converters. With the RSNS, the encoding errors (due to comparator thresholds not being crossed simultaneously) are eliminated, as is the need for the corresponding interpolation signal processing (reduced complexity). Computer generated data is used to help determine the properties of the RSNS. These properties include the largest dynamic range (number of distinct consecutive vectors), and the position of the largest dynamic range within the system. The position of the maximum unambiguous dynamic range is also quantified. Least squares analysis of 2 and 3 moduli systems are used to formulate closed-form expressions for the dynamic range. To compare the advantages of the RSNS with previously published results...

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## Application of the robust symmetrical number system to high resolution direction finding interferometry

Tipo: Tese de Doutorado

Português

Relevância na Pesquisa

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To reduce the number of phase sampling comparators in a direction finding (DF) interferometer antenna, a new array based on a robust symmetrical number system (RSNS) is described. The RSNS is used to decompose the spatial filtering operation into a number of parallel sub-operations that are of smaller computational complexity. Each sub-operation (interferometer) symmetrically folds the phase with folding period equal to 2Nm(i) where N is the number of channels that are used and n(i) the channel modulus. A small comparator ladder mid-level quantizes each folded phase response. Each sub-operation only requires a precision in accordance with that modulus. A much higher DF resolution is achieved after the N different RSNS moduli are used and the results of these low precision sub-operations are recombined. The parallel use of phase waveforms increases the antenna resolution without increasing the folding rate of the system. The new antenna is constructed and tested in an anechoic chamber, and the results are compared with the experimental results of a previously tested optimum symmetrical number system (OSNS) array. Although the dynamic range of the RSNS is somewhat less than the OSNS, the inherent Gray code properties make it attractive for error control in phase sampling interferometry.

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## Photonic Analog-To-Digital Conversion Using the Robust Symmetrical Number System

Fonte: The United States of America as
represented by the Secretary of the
Navy, Washington, DC (US)
Publicador: The United States of America as
represented by the Secretary of the
Navy, Washington, DC (US)

Tipo: Patente

Português

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Embodiments in accordance With the invention alloW for
direct digitization of Wideband RF signals Without the need
for doWn conversion or the use of mixers. In one embodiment,
a preprocessed input analog signal is applied to three Wide
band Mach-Zehnder interferometers (MZI), e.g., modulators,
to amplitude modulate a continuous Wave laser signal. A
photodetector is used at the output of each interferometer to
convert the amplitude modulated optical signal into an elec
trical signal. This is followed by an ampli?er and a loW-pass
?lter (LPF) to increase the signal level and to reduce the noise.
A small ml- comparator bank at the output of each LPF is
clocked at the sampling frequency and encodes the electrical
signal from each detector into a thermometer code that rep
resents an integer value Within the modulus. A ?eld program
mable gate array (FPGA) then combines the thermometer
code from each comparator bank in order to generate a more
convenient 6-bit binary representation, i.e., a digital output.

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## Extended Closed-form Expressions for the Robust Symmetrical Number System Dynamic Range and An Efficient Algorithm for its Computation

Fonte: Escola de Pós-Graduação Naval
Publicador: Escola de Pós-Graduação Naval

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http://dx.doi.org/10.1109/TIT.2014.2301820; The robust symmetrical number system (RSNS) is a number theoretic transform based on N > 2 sequences that can extract the maximum amount of information from symmetrical folding waveforms. The sequences, based on coprime moduli, exhibit an integer Gray code property making the RSNS well-suited for many applications that benefit from an inherent error detection and correction capability such as analog-to-digital converters, direction fnding arrays and radar waveform design. To use the RSNS, it is necessary to know the greatest length of combined sequences without ambiguities, called the dynamics range, M, for which only a few closed-form expresions currently exist. In this paper, an efficient algorithm for computing M and its position within the combined set of sequences is presented and shown to be independent of the size of the moduli. The algortihm is used to generate the equations for several groups of additional moduli arrangements. Closed form expressions for M are conjectured and proved using the obtained congruence equations that define the ambiguity locations.

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## Use of symmetrical number systems in electronic warfare

Fonte: Monterey California. Naval Postgraduate School
Publicador: Monterey California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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Approved for public release; distribution is unlimited.; The use of symmetrical number systems and wideband technologies is investigated to develop novel concepts for use in electronic warfare (EW) receivers. A computationally efficient algorithm for determining the dynamic range of the robust symmetrical number system (RSNS) is used to derive additional closed-form expressions for the RSNS dynamic range, using a curvefitting method. A photonic direction-finding array employing dual-electrode Mac-Zehnder modulators with RSNS preprocessing is developed and validated through simulations and experimental testing. Additional EW receiver concepts using the symmetrical number system (SNS) and CS are also examined. An SNS-CS cueing receiver is proposed that places a multichannel undersampling receiver, based on the SNS, into a CS framework and applies CS recovery algorithms to resolve the signal’s frequency components. The SNS-CS cueing receiver’s performance is evaluated through Monte Carlo simulations. The final concept examined is a multichannel Nyquist folding receiver (NYFR) with SNS-based uniform sampling rates (NYFR-B). The NYFR-B’s performance is evaluated through Monte Carlo simulations and performance curves are presented.

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## Extending the unambiguous range of CW polyphase radar systems using number theoretic transforms

Tipo: Tese de Doutorado
Formato: xx, 109 p. ;

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Approved for public release; distribution is unlimited.; Polyphase continuous waveform (CW) radar systems often use the popular Frank code and P4 code due to their linear time-frequency characteristics as well as their low periodic ambiguity sidelobes. The phase relationship of the Frank code corresponds to a sawtooth folding waveform. The phase relationship of the P4 code is symmetrical with a parabolic distribution. The radar system's unambiguous target detection range is limited by the number of subcodes within the code period (code length). Increasing the code length to extend the unambiguous range results in a larger range-Doppler correlation matrix processor in the receiver, a longer compression time and an increase in the receiver's bulk memory requirements. In addition, the entire code period may not be returned from the target due to a limited time-on-target resulting in significant correlation loss. To significantly extend the unambiguous range beyond a single code period, this thesis explores the relationship between the polyphase codes (Frank and P4) and the number theoretic transforms (NTT) where the residues exhibit the same distribution as the polyphase values. The unambiguous range is extended from the number of subcodes within a single code period to the dynamic range of the transform without requiring a large increase in correlation processing. The dynamic range of a NTT is defined as the greatest length of combined phase sequences that contain no ambiguities or repeated paired terms. By transmitting N 2 coprime code periods...

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## An analysis of three-channel RSNS virtual spacing direction finding system

Fonte: Monterey California. Naval Postgraduate School
Publicador: Monterey California. Naval Postgraduate School

Tipo: Tese de Doutorado
Formato: xiv, 75 p. : ill. ;

Português

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The design and performance analysis of a three-channel Robust Symmetrical Number System (RSNS) virtual spacing direction finding (DF) system was carried out in this thesis. The design was based on hardware used in the previous work in which a digital three-channel RSNS-based interferometer was built. In designing a RSNS virtual spacing DF system, it was found that the ratio between the modulus is an important parameter. The ratio affects the selection of the moduli set, the array size and the system's field of view. Based on the hardware used, the system's signal-to-noise ratio (SNR) was determined for a simulated emitter. Random Gaussian noise was injected into the system to determine the accuracy of mapping the actual angle-of-arrival (AOA) to the estimated AOA. Monte Carlo simulations were carried out to determine the probability of correctly estimating the AOA of the signal. Simulation results from the effect of spacing errors, phase errors, frequency error, moduli set change and SNR change was presented and analyzed. The RSNS-based DF system was found to be relatively insensitive to spacing error. A proposed two set of moduli were used to improve the accuracy and probability of correct estimation in both low SNR and high SNR conditions.; Republic of Singapore Air Force author.

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## Development of a digital tracking array with single-channel RSNS and monopulse digital beamforming

Tipo: Tese de Doutorado
Formato: xx, 111 p. : col. ill. ;

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Approved for public release; distribution is unlimited; Unmanned aerial vehicles (UAVs) are widely used in military applications, and one of the most common missions is remote sensing. Remote sensing requires UAVs equipped with different kinds of sensors. Information collected by remote sensors must be transmitted back to a ground control station (GCS) to conduct analysis. The majority of UAVs are controlled directly by GCS personnel using radio frequency (RF), line-of-sight (LOS) links. The ground antenna must acquire and then track the UAV signal. A digital phased array allows signal processing functions to be performed in the antenna processor as well as beamforming and tracking. The development of a digital tracking array with single-channel robust symmetrical number system (RSNS) and monopulse digital beamforming (DBF) to track a UAV's transmitted signal is described in this thesis. The RSNS is used as the direction finding (DF) algorithm and can provide high angle resolution with two closely spaced elements. However, as is typical for an array, the angle accuracy is reduced at the two ends of the field-of-view (FOV). The monopulse DBF is used to precisely track the signals. The monopulse tracking technique provides precise angle accuracy within a FOV of approximately Â±45. The tracking system is developed in LabView...

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## Photonic analog-to-digital converters preprocessing using the robust symmetrical number system for direct digitization of antenna signals

Tipo: Tese de Doutorado
Formato: xvi, 87 p. : col. ill. ;

Português

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Approved for public release; distribution is unlimited; The need to realize pervasive battlespace awareness is placing an increasing demand on the bandwidth and resolution performance of modern sensors, communication receivers and electronic warfare. Fundamental to realizing this demand is the omnipresent highspeed analog-to-digital converters. The need constantly exists for converters with lower power consumption. To reduce the number of power-consuming components, high-performance ADCs employ parallel configuration of analog folding circuits to symmetrically fold the input signal prior to quantization by high-speed comparators. In this thesis, a prototype of an optical folding 6-bit ADC utilizing a 7-bit preprocessing architecture was implemented using the Robust Symmetrical Number System (RSNS). The RSNS preprocessing architecture is a modular scheme in which the integer values within each modulus (comparator states), when considered together, change one at a time at the next position i.e. Gray-code property. MATLAB simulations are used to help determine the properties of the RSNS. These properties include the dynamic range (largest number of distinct consecutive vectors) and the location of the dynamic range within the number system. Since the waveform repeats every fundamental period...

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## Mixed signal processor for a robust symmetrical number system direction finding antenna

Formato: xvi, 100 p. : ill. (some col.) ; 28 cm.

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#Antennas (Electronics)#Robust symmetrical number system#Phase sampling interferometry#Direction finding#Ambiguity resolution#antennas.#

Approved for public release; distribution is unlimited.; Approved for public release; distribution is unlimited.; This applied research project has designed, simulated, constructed and tested the performance of a processing system for a prototype direction finding antenna. A mixed signal architecture to derive the direction of arrival from a Robust Symmetrical Number System (RSNS) encoded direction finding array is based on a new phase sampling interferometer approach that can be easily incorporated into established techniques to provide a high resolution, small-baseline array with few number of phase sampling comparators. The approach is based on preprocessing the received signal using the RSNS. The preprocessing is used to decompose the spatial filtering operation into a number of parallel suboperations (moduli) that are of smaller computational complexity. A much higher direction finding spatial resolution is achieved after the N different moduli are used and the results of the low precision suboperations are recombined, in addition to the reduction of the number of possible encoding errors due to the RSNS' inherent Gray-coding properties. This has resulted in a four inch antenna array being able to attain an angular resolution of less than 1.8 degrees with a continuous field of view of 120 degrees. The accompanying electronics occupy two 6 inch by 8 inch printed circuit boards...

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## Coordinated power-based control and utility interface converter in low voltage microgrids : Controle coordenado em microrredes de baixa tensão baseado no algoritmo power-based control e conversor utility interface; Controle coordenado em microrredes de baixa tensão baseado no algoritmo power-based control e conversor utility interface

Fonte: Biblioteca Digital da Unicamp
Publicador: Biblioteca Digital da Unicamp

Tipo: Tese de Doutorado
Formato: application/pdf

Publicado em 25/09/2015
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#Geração distribuída de energia#Conversores eletrônicos#Energia elétrica - Distribuição - Controle de qualidade#Eletrônica de potência#Sistemas elétricos de potência#Distributed generation system#Power electronic converters#Electrical energy#Power electronic#Power system

Esta tese apresenta uma possível arquitetura e sua respectiva estratégia de controle para microrredes de baixa tensão, considerando-se a existência de geradores distribuídos pela rede. A técnica explora totalmente a capacidade dos geradores distribuídos em ambos os modos de operação: conectado à rede e ilhado. Quando conectado à rede, sob o modo de otimização global, o controle busca a operação quase ótima da microrrede, reduzindo as perdas de distribuição e os desvios de tensão. Quando em modo ilhado, a técnica regula de forma eficaz os geradores distribuídos disponíveis, garantindo a operação autônoma, segura e suave da microrrede. A estratégia de controle é aplicada a uma estrutura de microrrede completamente despachável, baseada em uma arquitetura de controle mestre-escravo, em que as unidades distribuídas são coordenadas por meio do recém-desenvolvido algoritmo Power-Based Control. As principais vantagens da arquitetura proposta são a expansividade e a capacidade de operar sem sincronização ou sem conhecimento das impedâncias de linha. Além disso, a microrrede regula as interações com a rede por meio do conversor chamado de Utility Interface, o qual é um inversor trifásico com armazenador de energia. Esta estrutura de microrrede permite algumas vantagens como: compensação de desbalanço e reativo...

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