Reactively controlled directive arrays
TL;DR: The radiation characteristics of an N -port antenna system can be controlled by impedance loading the ports and feeding only one or several of the ports, and the direction of maximum gain can becontrolled by varying the load reactances.
Abstract: The radiation characteristics of an N -port antenna system can be controlled by impedance loading the ports and feeding only one or several of the ports. Reactive loads can be used to resonate a real port current to give a radiation pattern of high directivity. The theory of resonance is extended to include complex port currents and impedance loads. The initial design of an array is obtained by resonating a desired port current vector, which is then improved by an optimum seeking univariate search method. The direction of maximum gain can be controlled by varying the load reactances. Several numerical examples are given for a circular array of seven dipole elements.
Citations
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Patent•
01 May 2001TL;DR: In this paper, the phase control of re-radiated RF signals is addressed by determining the phase of each antenna element to enable the antenna apparatus to direct an antenna beam pattern toward a base station or access point with maximum gain, and consequently, maximum signal-to-noise ratio.
Abstract: An antenna apparatus, which can increase capacity in a cellular communication system or Wireless Local Area Network (WLAN), such as an 802.11 network, operates in conjunction with a mobile subscriber unit or client station. At least one antenna element is active and located within multiple passive antenna elements. The passive antenna elements are coupled to selectable impedance components for phase control of re-radiated RF signals. Various techniques for determining the phase of each antenna element are supported to enable the antenna apparatus to direct an antenna beam pattern toward a base station or access point with maximum gain, and, consequently, maximum signal-to-noise ratio. By directionally receiving and transmitting signals, multipath fading is greatly reduced as well as intercell interference.
384 citations
TL;DR: A new secret key generation and agreement scheme that uses the fluctuation of channel characteristics with an electronically steerable parasitic array radiator (ESPAR) antenna and has the ability to generate secret keys from the received signal strength indicator (RSSI) profile with sufficient independence is proposed.
Abstract: We describe a secure communication scheme that uses the random fluctuation of the natural environment of communication channels. Only the transmitter and the receiver share the communication channel characteristics. From reciprocity between a transmitter and a receiver, it is possible for them to share one-time information of their fluctuating channel. This can provide a secret key agreement scheme without key management and key distribution processes. In this paper, we propose a new secret key generation and agreement scheme that uses the fluctuation of channel characteristics with an electronically steerable parasitic array radiator (ESPAR) antenna. This antenna, which has been proposed and prototyped, is a smart antenna designed for consumers. Using the beam-forming technique of the ESPAR antenna, we can increase the fluctuation of the channel characteristics. From experimental results, we conclude that the proposed scheme has the ability to generate secret keys from the received signal strength indicator (RSSI) profile with sufficient independence.
348 citations
Cites methods from "Reactively controlled directive arr..."
...In this paper, we describe a new secret key generation and agreement scheme based on the fluctuation of channel characteristics by using the electronically steerable parasitic array radiator (ESPAR) antenna [9]–[17], which is a variable-directional antenna....
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Patent•
IBM1
TL;DR: In this article, the authors describe a reactively controlled directive antenna array that has a single central monopole or dipole as a radiating element excited directly by a feed system.
Abstract: A reactively controlled directive antenna array that has a single central monopole or dipole as a radiating element excited directly by a feed system. A plurality of parasitic elements surround the radiating element and through changing the state of the parasitic impedance causing the antenna to be in an omni directional or beam pointing mode according to whether the parasitic elements are open circuited or short circuited. A computer modem and memory including stored programs control the antenna array in an omnidirectional or directive mode to locate, identify and communicate with nodes in a wireless communication network. A stored table is created in the memory indicating the antenna direction for communicating with each node in the network. Using the stored table, the computer initiates a communication sequence with a selected node, the sequence having the advantages of improved signal sensitivity and angular discrimination for wireless communication systems.
295 citations
TL;DR: A fast beamforming algorithm based on simultaneous perturbation stochastic approximation with a maximum cross correlation coefficient criterion is proposed and the simulation and experimental results validate the algorithm.
Abstract: A low-power consumption, small-size smart antenna, named electronically steerable parasitic array radiator (ESPAR), has been designed. Beamforming is achieved by tuning the load reactances at parasitic elements surrounding the active central element. A fast beamforming algorithm based on simultaneous perturbation stochastic approximation with a maximum cross correlation coefficient criterion is proposed. The simulation and experimental results validate the algorithm. In an environment where the signal-to-interference-ratio is 0 dB, the algorithm converges within 50 iterations and achieves an output signal-to-interference-plus-noise-ratio of 10 dB. With the fast beamforming ability and its low-power consumption attribute, the ESPAR antenna makes the mass deployment of smart antenna technologies practical.
256 citations
Cites background from "Reactively controlled directive arr..."
...Wireless operators are currently searching for new technologies which would be implemented into the existing wireless communications infrastructures to provide the broader bandwidth per user channel, the better quality and new value-added services....
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Patent•
28 Oct 2003TL;DR: In this article, an antenna array that can increase capacity in a wireless communication system is disclosed, which comprises a plurality of antenna elements (101-n), each coupled to a respective weight control component (111-n) to provide a weight to the signal transmitted from (or received by) each element.
Abstract: An antenna apparatus that can increase capacity in a wireless communication system is disclosed. The antenna operates in conjunction with a station and comprises a plurality of antenna elements (101-n), each coupled to a respective weight control component (111-n) to provide a weight to the signal transmitted from (or received by) each element. The weight for each antenna element is adjusted to achieve optimum reception during, for example, an idle mode when a pilot signal is received. The antenna array creates a beam former for signals to be transmitted from the mobile station, and a directional receiving array to more optimally detect and receive signals transmitted from the base station. By directionally receiving and transmitting signals, multipath fading and intercell interference are greatly reduced. The weights are adjusted in a coarse and a fine mode. In the coarse mode all the weight control components are jointly adjusted or changed so that the antenna beam scans through a predetermined sector of a circle until a signal quality metric of the received signal is optimized. The coarse adjustment mode is followed by a fine adjustment mode during which the weights of are independently adjusted to further optimize the signal quality metric.
239 citations
References
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Book•
01 Jan 1968
TL;DR: This first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis.
Abstract: From the Publisher:
"An IEEE reprinting of this classic 1968 edition, FIELD COMPUTATION BY MOMENT METHODS is the first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems. It presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis. Written especially for those who have a minimal amount of experience in electromagnetic theory, this book illustrates theoretical and mathematical concepts to prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems.Written especially for those who have a minimal amount of experience in electromagnetic theory, theoretical and mathematical concepts are illustrated by examples that prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems."
6,593 citations
2,808 citations
1,152 citations
TL;DR: A survey of computational methods in linear algebra can be found in this article, where the authors discuss the means and methods of estimating the quality of numerical solution of computational problems, the generalized inverse of a matrix, the solution of systems with rectangular and poorly conditioned matrices, and more traditional questions such as algebraic eigenvalue problems and systems with a square matrix.
Abstract: The authors' survey paper is devoted to the present state of computational methods in linear algebra. Questions discussed are the means and methods of estimating the quality of numerical solution of computational problems, the generalized inverse of a matrix, the solution of systems with rectangular and poorly conditioned matrices, the inverse eigenvalue problem, and more traditional questions such as algebraic eigenvalue problems and the solution of systems with a square matrix (by direct and iterative methods).
667 citations
TL;DR: It is found that the maximum gain obtainable from a broad-band antenna is approxima tely equal t o that of the uniformly Illuminated aperture, and if higher gain is desired, the antenna mus t necessarily be a narrow-band device.
Abstract: A theore tical analysis is made of the effect of antenna s ize on parameters such as gain, bandwidth, and efficiency . Both near-zone and far-zon e direct ive gains are considered . It is found that t he maximum gain obtainable from a broad-band antenna is approxima tely equal t o that of the uniformly illumina ted aper t ure. If higher gain is desired , the antenna mus t necessarily be a narrow-band device. In fact, th e input impedance becomes frequency sensitive so r apidly that, for large antennas, no significant increase in gain over tha t of the uniformly illuminated aper t ure is possible. Also, if t he antenn a is lossy, t he efficiency falls rapidly as the gain is increased over that of the uniformly illumina ted aperture.
663 citations