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Topic: Antenna arrays

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	Antenna Arrays
		Antenna arrays principles and properties are discussed using an interactive applet.
		Antenna arrays are formed by assembling identical (in most cases) radiating elements such as dipoles for example.
		Antenna arrays are characterized by their array factor which is given by the formula
	www.analyzemath.com /antenna_tutorials/antenna_arrays.html (333 words)

	Phased Array Antennas - Microwave Encyclopedia - Microwaves101.com
		The physics behind phased arrays are such that the antenna is bi-directional, that is, they will achieve the same steerable pattern in transmit as well as receive.
		In an array, the pattern does vary considerably with frequency due to element spacing (measured in wavelengths) and the frequency sensitivity of the phase shifting networks.
		Gain in a phased array is both a function of the individual element gain and the number of elements.
	www.microwaves101.com /encyclopedia/phasedarrays.cfm (1330 words)

	P3-D Antenna Design
		Antenna pointing is done by positioning the entire spacecraft during the orbit so that the high gain antennas are Earth pointing.
		Patch antennas do not need to employ high dielectric materials in their construction, hence the references herein will be to "patch" rather than "microstrip" antennas, and will use air (or space vacuum) as the dielectric.
		This antenna is two wavelengths in diameter and has a 1/4 wavelength high outer ring with a 1/2 wavelength high post in it's center supporting a turnstile at 1/4 wavelength high and a 1/2 wave circular reflector.
	www.amsat.org /amsat/sats/phase3d/antennas.html (2795 words)

	How To Become An Antenna Guru
		If the antenna is electrically large, the pattern will have more structure, that is more peaks and nulls and the more directive will be the main lobe as shown in figure 4 for a dipole antenna that is 10.25 wavelengths long.
		The beamwidth of an antenna is a measure of the directivity of an antenna and is usually defined by the angles where the pattern drops to one half of its peak value or known as the 3db points.
		As was said before, an antenna is a structure carrying an electrical current and the electrical properties of the antenna depends upon the distribution of that current in magnitude and phase.
	www.borg.com /~warrend/guru.html (4657 words)

	The HAARP Antenna Array (Site not responding. Last check: 2007-10-19)
		The HAARP antenna array is similar or identical to many other types of directive antenna types in use for both military and civilian applications including air traffic control radar systems, long range surveillance systems, steerable communication systems and navigation systems.
		While the shape of the antenna pattern can be tailored by careful choice of the amplitude of the individual element excitations, the angle at which the pattern maximum occurs can be changed by adjusting the phase of the excitations of each of the antenna elements.
		The amount of gain that is obtainable in an antenna array (remember, gain refers to the highest signal strength at the pattern maximum) is directly related to the narrowness of the antenna pattern.
	www.haarp.alaska.edu /haarp/ant3.html (1504 words)

	CASA - Finite Antenna Arrays, An Eigencurrent Approach
		The two main goals of the design of such an antenna are: the energy induced in the antenna as electromagnetic radiation should be radiated in a specific direction and the transfer of energy from source to electromagnetic radiation should be optimal.
		On basis of this observation, a first-order approximation of the behavior of the behavior of line arrays with complex elements is described by the coefficient distributions of the eigencurrents of line arrays with simpler elements.
		On basis of this observations, a first-order approximation of the behavior of line arrays with complex elements is described by the coefficient distributions of the eigencurrents of a single strip with piecewise expansion functions.
	www.win.tue.nl /casa/research/casaprojects/bekers.html (1611 words)

	Antenna arrays
		Driven arrays, in which all the radiating elements are connected to the energy source, have smaller losses than parasitic arrays while retaining some of the narrow-beam characteristics.
		The radar antenna is frequency sensitive and radiates pulses at an elevation angle determined by the applied frequency.
		The slot antenna is compared to its complementary dipole to illustrate that the radiation patterns produced by a slot antenna cut into an infinitely large metal sheet and that of the complementary dipole antenna are the same.
	www.tpub.com /neets/book11/46c.htm (1444 words)

	Phased Antenna Arrays: X-Band Low Profile (Site not responding. Last check: 2007-10-19)
		To reduce the sidelobes and the weight, the array is made elliptical and features a unique distribution of the EM field over the aperture.
		MERA's phased antenna arrays are developed on the basis of the microstrip, waveguide slot, and travelling wave elements.
		Such array is capable of operating both in the regular single-beam transmit-receive mode and in the mono-impulse with sum-difference pattern mode.
	www.meranetworks.com /technologies/antenna_tech/xband_low.html (166 words)

	Lifting the Limits on High-Speed Wireless Data Access Using Antenna Arrays
		Here, base station antenna arrays are the enabling tools for a wide range of spatial processing techniques devised to enhance desired signals and mitigate interference [6].
		Antennas within a terminal are assumed fully uncorrelated, whereas those within a base station sector are assumed either also uncorrelated (for sufficiently large spacing) or fully correlated (for close spacing and coherent operation).
		While the deployment of base station antenna arrays is becoming universal, it is really the simultaneous deployment of base station and terminal arrays that unleashes vast increases in capacity and data rates by opening up multiple signaling dimensions.
	www.comsoc.org /pubs/sample/ci1/Private/2001/Sep/lozano.html (5036 words)

	Deep Space Network: Technology Basics: DSN Antenna Arrays (Site not responding. Last check: 2007-10-19)
		Some of the antennas are arranged such that their signals can be combined to provide improved performance through a process called "arraying." When antennas are arrayed, more of a spacecraft's signal can be captured, and the result is higher data rates.
		The first time intercontinental arraying was implemented between antennas at two separate complexes was for the Galileo spacecraft's prime mission when it gathered science data from Jupiter and its moons.
		Arraying was utilized to collect more of the weak signal sent from the low-gain spacecraft antenna necessitated by difficulties with the high-gain antenna.
	deepspace.jpl.nasa.gov /dsn/brochure/tech_basics/arrays.html (137 words)

	Antenna directivity and effective area
		Indeed, it is topologically impossible for an antenna to emit transverse waves uniformly in all directions (for the same reason that it is impossible to comb the hair on a sphere in such a manner that there is no parting).
		One of the aims of antenna engineering is to design antennas which transmit most of their radiation in a particular direction.
		In the theory of electrical circuits, a receiving antenna is represented as an e.m.f connected in series with a resistor.
	farside.ph.utexas.edu /teaching/jk1/lectures/node83.html (944 words)

	Books on Antenna Arrays (Site not responding. Last check: 2007-10-19)
		A periodic surface is an assembly of identical elements arranged in a one or two-dimensional array.
		Modern antenna techniques are discussed for single patches, dual linear and circular polarizations designs, and arrays used in mobile communications.
		Phased Array Antennas is geared to the interests of both the practicing design engineer and the antenna array analyst.
	books.bankhacker.com /Antenna+Arrays (646 words)

	Antenna Technology (Site not responding. Last check: 2007-10-19)
		The X-band microstrip antenna array with electronic beam scanning has been designed on the basis of three-layer microstrip lines, X-band PCB with 0.06 inch thick substrate RO3003.
		The S-band waveguide multi-beam antenna array has been developed on the basis of the traveling wave elements and is capable of forming from five to eight vertically oriented fan beams simultaneously.
		The antenna's distinctive features are a wide beam for the transmitting mode and low level sidelobes for the receiving and transmitting modes.
	www.meranetworks.com /technologies/antenna_tech/index.html (228 words)

	3G Wireless Capacity Optimization for Widely Spaced Antenna Arrays
		However, the correlation between received signals for this configuration is high, and as a result reduces the ability of an antenna array to combat against fading (i.e., the lack of space diversity) [4].
		The array antenna is circular with four elements distance d apart arranged along the x and y axes.
		Finally, it is shown that an adaptive array antenna with large antenna spacing at the base station can significantly improve the performance for both uplink and downlink transmissions in a slow fading channel with co-channel interference.
	www.comsoc.org /pci/private/2000/dec/jana.html (2767 words)

	Adaptive arrays
		The array adapts itself to form a main lobe, with its direction and bandwidth determined by the pilot signal, and to reject signals or noises occurring outside the main lobe.
		The output of the parallel auxiliary array is subtracted from the main channel.
		The output of the array y(t) is the weighted sum of the received signals si(t) with gain gm(θ,Φ) and the noise n(t) from the receivers.
	www.people.cornell.edu /pages/zf24/Adaptive_arrays.htm (1405 words)

	Antennas Online (Site not responding. Last check: 2007-10-19)
		The antenna solutions are also based on the use of adjustable components that when used with a suitable remote control system can provide greater flexibility and superior optimization of the network.
		This antenna is well suited for in-car diversity configurations, as the automotive industry strives to remove antennas from outside the car and place them inside.
		It will also discuss the requirements for antennas that will be necessary for the radios to take full advantage of their inherant capabilities; for instance, the current military development program in the US envisions software radios covering a range from 2 MHz to 2 GHz.
	www.antennasonline.com /ast_conf_program.htm (1650 words)

	Antenna arrays
		An array of antenna elements is a spatially extended collection of N similar radiators or elements, where N is a countable number bigger than 1, and the term "similar radiators" means that all the elements have the same polar radiation patterns, orientated in the same direction in 3-d space.
		A Yagi-Uda antenna may be thought of as an array of dipoles with different amplitudes and phases of the dipole currents.
		The array pattern is the polar radiation pattern which would result if the elements were replaced by isotropic radiators, having the same amplitude and phase of excitation as the actual elements, and spaced at points on a grid corresponding to the far field phase centres of the elements.
	www.ee.surrey.ac.uk /Personal/D.Jefferies/antarray.html (1039 words)

	FPGAs make smart antenna arrays a reality (April 2005) - Features - Wireless Web
		Smart antenna arrays comprise several antennas working in conjunction with an intelligent system that processes the received and transmitted data.
		However, smart antenna arrays provide a much more effective solution by focusing the transmitted power towards the user and only looking in the direction of the user for the uplink signal.
		Adaptive antenna arrays employ a more intelligent control system that monitors the radio environment and, in particular, the characteristics of the signal path between the user and the base station.
	wireless.iop.org /articles/feature/6/4/4/1?rss=2.0 (1142 words)

	RETRODIRECTIVE ANTENNA ARRAYS
		However to conform the 360 degree coverage of the array, a four-element retrodirective array using monopole antenna as array elements was also tested.
		A typical measured radiation pattern for a two-element monopolar retrodirective antenna array is shown in figure 3.
		In this way a retrodirective array can be used in a mobile communication applications to simultaneously track a number of units as shown in figure 6.
	www.ee.qub.ac.uk /hfe/retro_active.html (395 words)

	ATI's Antenna and Antenna Array Fundamentals course
		Different types of antennas such as dipole, loop, patch, horn, dish, and helical antennas are discussed and compared and contrasted from a performance/applications standpoint.
		Antenna arrays are discussed, and array factors for different types of distributions (e.g., uniform, binomial, and Tschebyscheff arrays) are analyzed giving insight to sidelobe levels, null locations, and beam broadening (as the array scans from broadside.) The end-fire condition is discussed.
		He is active in the IEEE and is presently on the steering committee for the Antennas and Propagation Conference for 2005.
	www.aticourses.com /antenna_fundamentals.htm (693 words)

	Randtron Antenna Systems Flared Notch Technology
		The antenna is capable of large bandwidths (greater than 3:1) and the solid metal element is capable of handling large amounts of high power.
		The K-band and S-band arrays use flared notch elements to provide linear polarization, while a patch antenna is used to develop circular polarization at L-band.
		When an antenna with wide angle electronic scanning, wide bandwidth, and high power capacity is needed for your radar or communications requirement, call on Randtron Antenna Systems to see how a flared notch antenna can be utilized in your application.
	www.l-3com.com /randtron/flarednotch.htm (220 words)

	Antenna arrays (Site not responding. Last check: 2007-10-19)
		Antenna arrays can either be periodic in the x direction or periodic in both the x and y directions.
		In this case, the only difference between the model of a periodic antenna array and that of a grating is the excitation and the explicit definition of the complex factor Cx that is not required for gratings.
		Periodic boundaries for antenna arrays are the same as for gratings.
	alphard.ethz.ch /hafner/MaX/WinHlp40/Antennaarrays.htm (327 words)

	Antenna Arrays and Clutter Rejection (Site not responding. Last check: 2007-10-19)
		I propose to improve the KU wideband radar by using an antenna array with adaptive beamforming capabilities in the cross-track direction.
		Develop space-time characterization of the desired signal and clutter and determine the optimum number of antenna array elements required to eliminate clutter.
		Since the spatial spread of clutter incident on the receive array is limited, we can use an antenna array to produce nulls in the directions of clutter (Figure 3b).
	www.ittc.ku.edu /~rvc/html/array_proposal.html (1935 words)

	HyperGain® Antenna Arrays - Sectorized Omnidirectional
		Each of the antennas in the array can be adjusted individually to compensate for the geography of the installation location.
		Each of the three antennas in this array can be adjusted individually (0-20° up or down tilt) to compensate for the geography of the installation location.
		Since this array is horizontally polarized, it is ideal for use in areas susceptible to the affects of interference generated by commonly used vertically polarized wireless LAN equipment.
	www.hyperlinktech.com /web/antenna_array.php (534 words)

	Antenna arrays
		In the direction perpendicular to the array, all elements contribute in phase, and the intensity is proportional to the square of the sum of the individual amplitudes.
		Thus, it is possible to construct a very high gain antenna by arranging a large number of low gain antennas in a regular pattern and driving them in phase.
		In fact, it is possible to produce a radar beam which sweeps around the horizon, without any mechanical motion of the array, by varying the phase difference between successive elements of the array electronically.
	farside.ph.utexas.edu /teaching/jk1/lectures/node84.html (617 words)

	Antenna arrays
		The antenna array consists of four circular patches, each of which are excited by a coaxial feed, placed slightly off-center.
		This octagon antenna array consists of eight patch antennas, which are fed by a microstrip circuit connected to a coaxial line.
		Antenna Arrays are a very powerfull way to set up a lot of antennas together on a small area.
	www.cst.de /Content/Articles/index3.aspx (97 words)

	Ingenuity - March 2002 - Professor's antenna arrays steer clear of interference
		ECE Assistant Professor Jennifer Bernhard's (standing) reconfigurable antenna plan was one of over a thousand submitted to NASA in response to a request for proposals in various research areas.
		Bernhard's plan is to design and build arrays whose elements (individual antennas) are reconfigurable and thus can "steer" their transmitted beams with unprecedented agility.
		Michielssen will develop an array simulator that can account for the individual radiation patterns of all the elements-no mean computational feat.
	www.ece.uiuc.edu /ingenuity/302/index.html (670 words)

	[No title] (Site not responding. Last check: 2007-10-19)
		In this thesis, we study wireless multiuser communication systems in the regime of low spectral efficiencies, where users and the multiple access point are equipped with antenna arrays.
		Finally, we address the paradigm of statistically correlated antenna arrays, where we derive the effective number of uncorrelated receive spatial dimensions, which we partition to represent users policies.
		As more correlated antennas are packed into a limited area we show that effective receive dimensionality converges to a finite limit which we evaluate for some simple geometries.
	cmc.rice.edu /docs/docinfo.aspx?doc=Muh2004May3Capacityof (314 words)

	Software View (Site not responding. Last check: 2007-10-19)
		An interactive antenna pattern visualization package "APV" is developed to generate and display the far field patterns of different antennas and antenna arrays.
		In addition to standard antenna geometries, the software permits one to visualize in an interactive procedure, the array factors of different types of antenna arrays.
		Among those arrays are the linear uniform and non-uniform arrays, Binomial arrays, Dolph-Tschebyscheff linear arrays, rectangular and circular two dimensional arrays, and cubic and spherical three dimensional arrays.
	aces.ee.olemiss.edu /downloadsoftware.asp?Action=View&File=2 (255 words)

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