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Chaotic synchronization in small assemblies of driven Chua's circuits

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS 2000年第5期47卷 644-654页

作者： Sánchez, E Matías, MA Pérez-Muñuzuri, V Univ Salamanca Escuela Tecn Super Ingn Ind E-37700 Salamanca Bejar Spain Univ Illes Balears CSIC Inst Mediterraneo Estudios Avanzados E-07071 Palma de Mallorca Spain Univ Santiago de Compostela Fac Phys Grp Nonlinear Phys E-15706 Santiago Spain

Chaotic synchronization is studied in experiments performed on dynamic arrays of Chua's circuits that are connected by using a recently introduced driving method especially suited for the design of such arrays. Namely;the driven circuit has the same number of energy storage elements as the driving circuit. The experimental results, which are supported by theoretical analysis, are different depending on the geometric arrangement of the array, In the case of linear arrays, the first circuit always imposes its behavior to the rest of the chain at a finite velocity, Instead, in the case of ring geometries, the chaotic synchronized state is only stable up to a certain size of the ring. Beyond this critical size a desynchronizing bifurcation occurs, leading to a chaotic rotating wave that travels through the array, This instability is explained by performing an analysis in terms of modes.

关键词： chaotic synchronization Chua's circuit dynamic arrays pattern forming instabilities

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Array Phase Center dynamics Using Spatial Amplitude Modulation for High-Efficiency Secure Wireless Communication

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2024年第1期72卷 487-496页

作者： Randall, Jacob R. Merlo, Jason M. Arisheh, Amer Abu Nanzer, Jeffrey A. Michigan State Univ Dept Elect & Comp Engn E Lansing MI 48824 USA

We present an approach to secure wireless communication based on dynamically changing the apparent phase center (PC) of a two-element antenna array using spatial amplitude dynamics. We implement PC dynamics by modulating the relative amplitudes of the signals fed to two antenna elements. By moving the PC symmetrically with respect to the geometric center of the array, the far-field amplitude pattern remains mostly constant while the phase pattern changes, imparting modulation onto the transmitted or received signals that is a function of the angle. The resulting directional modulation (DM) effectively scrambles the information in the radiated waveform at angles outside of the information beam, where the modulation impacts are negligible. The result is a narrow region where information is recoverable, and since the radiated power does not change, the efficiency remains high. We present the design of a 2.5-GHz two-element array with asymmetric amplitude modulation and characterize the PC location as a function of the amplitude ratio between the elements. We demonstrate secure wireless communication experimentally in a high signal-to-noise ratio (SNR) environment, demonstrating the reduction in throughput due solely to the PC dynamics. Finally, we analyze the information beamwidth (IB) and present a design procedure relating the amplitude ratio, SNR, element spacing, and QAM modulation format to the IB.

关键词： Antennas Antenna measurements Antenna radiation patterns Switches Phased arrays Signal to noise ratio Phase modulation Directional modulation (DM) dynamic antennas dynamic arrays phase center (PC)

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Millimeter-Wave Angle Estimation of Multiple Targets Using Space-Time Modulation and Interferometric Antenna arrays

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2021年第11期69卷 5126-5134页

作者： Vakalis, Stavros Nanzer, Jeffrey A. Michigan State Univ Dept Elect & Comp Engn E Lansing MI 48824 USA

A new method of angle estimation of multiple targets using a distributed interferometric antenna array and wideband space-time modulation generating a dynamic array pattern is presented in this work. Interferometric array measurements of angle of arrival are generally ambiguous in the presence of two or more targets. We propose a new method of mitigating ambiguities in interferometric measurements by multiplying the angle pseudo-spectra from multiple antenna baselines, resulting in detections at only the angles of the targets. Using a single linear frequency-modulated transmitter and a receive interferometric array with N elements, we show a simple and computationally efficient technique to estimate the angle of up to O(N-2) targets. We describe the theory behind the technique, present detailed simulations, and provide an experimental verification using a three-element millimeter-wave measurement system.

关键词： Angle estimation correlator arrays dynamic arrays interferometric antenna arrays interferometry radar space-time modulation target detection

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A dynamic Array Using Spatial Amplitude Modulation With an Asymmetric Wilkinson Power Divider for Secure Wireless Applications

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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS 2023年第12期22卷 3107-3111页

作者： Randall, Jacob R. Abu Arisheh, Amer Merlo, Jason M. Nanzer, Jeffrey A. Michigan State Univ Dept Elect & Comp Engn E Lansing MI 48824 USA

A new method of obtaining directional modulation by implementing antenna array dynamics is proposed. An asymmetric switching feed structure is implemented in a two-element array that supports a static antenna pattern in a desired direction while adding sufficient complex modulation at other angles to mitigate the transfer of information. The dynamic antenna array feeds are calibrated to be in-phase, have a signal feed amplitude ratio of approximately 6.15 +/- 0.1 dB through the design of an asymmetrical Wilkinson divider. The antenna system comprises of a two-state switching matrix using a double-pole double-throw (DPDT) RF switch. Secure communication capability is demonstrated in simulation and experiment by a 2.5 GHz two-element patch array. The communication system uses a 16-quadratic-amplitude modulation single-carrier signal transmitting 48 kb in a pseudorandom bit sequence at a rate of 4 Mb/s. The DPDT switch was controlled using a switching rate of 3 kHz. To isolate the effects of the phase dynamics, the communication system was operating at an signal-to-noise ratio of 33 dB, thus transmitting high power to all directions. A low bit error ratio (BER) of <10(-3) is demonstrated at the desired transmission direction phi <= |13(degrees)| , with higher BER outside this region. A measurement of a static antenna yielded BER =0 in all directions;thus, the bit errors and narrow +/- 13(degrees) information beamwidth were due exclusively to the antenna array dynamics. Performance metrics of this directional modulation technique are compared against previous literature for the reader. Further insights to spurious signals and mitigation are taken into consideration for the equipment and instrumentation of a narrowband signal to validate the technique as a viable "black-box" system implementation.

关键词： Switches Antenna arrays Antennas Antenna measurements Wireless communication Modulation Antenna feeds Directional modulation (DM) distributed array dynamic antennas dynamic arrays secure wireless

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THE DESIGN AND IMPLEMENTATION OF PARAMETRIC TYPES IN PASCAL

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SOFTWARE-PRACTICE & EXPERIENCE 1982年第2期12卷 169-184页

作者： HENNESSY, J ELMQUIST, H STANFORD UNIV DEPT COMP SCISTANFORDCA 94305

Parametric types offer an attractive solution to the problems of dealing with arrays in Pascal. These problems arise from the use of strong, static type checking, especially of array-type procedure arguments. Parametric types provide solutions both for the array procedure argument problem and allow the consistent inclusion of arrays with dynamic bounds. A parametric type mechanism is proposed and design issues are discussed. The inclusion of parametric types has major effects on the implementation of a language like Pascal. The implementation issues and implementation versus design tradeoffs are examined. The implementation strategy used can be extended to accommodate the standard and generic types in Ada.

关键词： Parametric types Compiler design Type structure dynamic arrays Pascal

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Immediate-Access Indexing Using Space-Efficient Extensible arrays 22

Immediate-Access Indexing Using Space-Efficient Extensible A...

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Proceedings of the 26th Australasian Document Computing Symposium

作者： Alistair Moffat Joel Mackenzie School of Computing and Information Systems The University of Melbourne Australia School of Information Technology and Electrical Engineering The University of Queensland Australia

ISBN: (纸本)9798400700217

The array is a fundamental data object in most programs. Its key functionality – storage of and access to a set of same-type elements in O(1) time per operation – is also widely employed in other more sophisticated data structures. In an extensible array the number of elements in the set is unknown at the time the program is initiated, and the array might continue to grow right through the program’s execution. In this paper we explore the use of extensible arrays in connection with the task of inverted index construction. We develop and test a space-efficient extensible array arrangement that has been previously described but not to our knowledge employed in practice, and show that it adds considerable flexibility to the index construction process while incurring only modest run-time overheads as a result of access indirections.

关键词： dynamic arrays text querying Extensible arrays text indexing

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