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Topic: Phased array

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	Phased array - Wikipedia, the free encyclopedia
		In telecommunication, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.
		A phased array may be used to point a fixed radiation pattern, or to scan rapidly in azimuth or elevation.
		Phased arrays are required to be used by many AM broadcast stations to enhance signal coverage in the city of license, while minimizing interference to other areas.
	en.wikipedia.org /wiki/Phased_array (1002 words)

	Phased Array Antennas - Microwave Encyclopedia - Microwaves101.com (Site not responding. Last check: 2007-10-23)
		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.
		Phase shifters are mostly used in phased array antennas (radar systems).
		A linear phased array with equal spaced elements is easiest to analyze and forms the basis for most array designs.
	www.microwaves101.com /encyclopedia/phasedarrays.cfm (1080 words)

	AEW&C - Phased Array Technology Parts 1 & 2
		Phased array antenna technology has been in use for some decades, but most applications have been confined to ground based systems, due significant weight and size penalties associated with older families of electronic devices.
		The phased array's ability to almost instantaneously change beam direction and shape in fact adds a whole new dimension to tracking, as multiple targets may be tracked by multiple beams, all of which are interleaved in time with a periodically scanning search beam.
		Clearly as the technology of active phased arrays matures, designers will settle upon the most suitable configurations, but as is often the case, the simple and orthodox solutions may ultimately prevail simply because they were a good idea in the first place.
	www.ausairpower.net /aew-aesa.html (4905 words)

	Phased Array Antenna
		Phased array antennas have low visibility, the difficulty to detect due to the fact that there are no moving parts.
		Phased array antennas have the character of quick steering, either electrical or optical controlled.
		Having so many advantages over a single antenna, phased array antennas are widely used in both civilian operations, such as in air traffic, smart antennas, and broadcast satellite communications, and military areas, such as in marine radar, airborne radar, missile guidance, trajectory determination, and satellite communications.
	www.mrc.utexas.edu /Chen/optic-inter/Phased_Array_Antenna.htm (795 words)

	BBC - h2g2 - Phased Array Antennae - A743799
		In order to understand how an array antenna works, the basic wave superposition principle which was outlined in the entry about Antennae must be applied twice: the radiating elements can be thought of as consisting of radiation sources whose contributions are added in order to yield the directional pattern of the device.
		Arrays and single feed antennae produce a beam which can only be moved in space by either moving the reflector, the feeder or the whole construction.
		The term 'phased array' originates from the fact that when considering sinusoidal signals such as electromagnetic waves, time delay can be translated as a shift of the phase of the signal.
	www.bbc.co.uk /dna/h2g2/alabaster/A743799 (1075 words)

	[No title]
		The technique of connecting mismatched feeders to the driven elements in a phased array is an expedient method for obtaining relative current phases in the elements that approximate the desired currents.
		If the phase of the current in one element is 90 degrees out of phase with the other, then the fields radiated from these elements are in phase in one direction, and out of phase in the opposite direction.
		We would expect the relative phase in the first case to be less than it is in the second case, since the difference in physical line lengths is 6 inches in the first case and 20 inches in the second.
	www.qsl.net /km5kg/array.htm (7955 words)

	Phased Array (Site not responding. Last check: 2007-10-23)
		By setting the appropriate phase delays in each of the elements before all the signals are summed, the array in effect can "point" to a given location on the sky to maximize its sensitivity to that location.
		Since the phasing of the array is accomplished through the use of rf PIN diodes, the time required to calculate phase delays and "point" to a given location is measured in milliseconds.
		An important feature in the receiver section of this array will be multiple spectral channels provided by a series of narrow-band rf filters within the 151 MHz radio astronomy band, and the signature of a broadband GRB radio counterpart would be a temporally dispersed signal across these channels.
	laastro.lanl.gov /fho/phased_array.htm (645 words)

	Phased-Array Simulation For Antenna Test Range Design
		The approach taken is to simulate near-field data for a phased array antenna and to introduce specific mechanical and electrical inaccuracies and to study the impact that these will have on the far-field measurement result through comparison to the perfect case (no introduced inaccuracies).
		For the array, a Taylor aperture distribution is assumed in the horizontal direction and a constant distribution in the vertical direction.
		The near-field scan is simulated for a probe at a distance of 0.1m away from the array face and covering a scan area of 1.9m x 1.9m to allow far-field angular coverage from –80 to +80 degrees in both azimuth and elevation.
	www.nearfield.com /amta/Amta98_djr.htm (1752 words)

	NDE Associates, Inc. - Ultrasonic Testing - Phased Array (Site not responding. Last check: 2007-10-23)
		In addition, the phased array results are displayed in a image that is easier to interpret than the results of conventional A-scan.
		Kumar is using phased array inspection as a follow-up to TOFD.
		Phased array inspection of offshore riser pipe welds with 5 MHz 16 element array.
	www.nde.com /phased_array.htm (188 words)

	Amazon.ca: Phased Array Antennas: Books: R. C. Hansen (Site not responding. Last check: 2007-10-23)
		Phased Array Antennas is geared to the interests of both the practicing design engineer and the antenna array analyst.
		Phased Array Antennas is an indispensable tool-of-the-trade for antenna design engineers, radar engineers, PCS engineers, and communications engineers.
		Phased array antennas have many important applications, including radar uses in airport surveillance and missile detection and tracking, as well as applications in personal communication systems and in satellite communications.
	www.amazon.ca /Phased-Array-Antennas-R-Hansen/dp/047153076X (602 words)

	Interchannel Crosstalk Evaluation in a Prototype Phased Array Ultrasound System Designed for Hyperthermic Cancer Therapy
		The phased array system is tested in a water tank using a two-dimensional positioning system and a hydrophone.
		Array steering is improved with shape calibration, which is a triangulation procedure that determines the spatial orientation of the individual array elements with respect to the coordinate axes defined by the positioning system.
		Thus, the measured crosstalk values for this prototype ultrasound phased array are in an acceptable range for shape calibration.
	www.egr.msu.edu /~mcgough/research/chormand/chormand.htm (606 words)

	Acoustic Applications of Phased Array Technology
		Phased arrays synthesize larger apertures from an array of elements.
		Phased arrays get around the beam width limit by using several small apertures to achieve the same result as one large aperture.
		Similar arrays feature the ability to monitor surface waves height (the height variation of the water causes pressure fluctuations in the depths) and to monitor local marine life.
	casa.colorado.edu /~danforth/science/sonar/sonar1.html (2782 words)

	Phased arrays and Jan C Somer
		In the phased-array system, all the elements of an array were used for each interrogation pulse and variable time delays were introduced between the various elements, both on transmission and reception, in such a way that effective launching and reception of an acoustic wave occurred predominantly in one defined direction.
		Grating lobes are unique to array transducers and are caused by the regular, periodic spacing of the small array elements.
		Similar to linear array designs, focusing in the direction at right angles to the scan plane determines the slice thickness and is accomplished by use of accoustic lens.
	www.ob-ultrasound.net /somers.html (1472 words)

	New Radar Technology Can Increase Tornado Warning Lead Times
		Phased array radar technology may help forecasters of the future provide earlier warnings for tornadoes and other types of severe and hazardous weather.
		The phased array radar project has begun a new stage in NSSL's leadership in the research and development of future generations of weather radar.
		Early tests of the phased array radar system show that the technology has the potential to vastly improve upon the capabilities of the national NEXRAD radar network for all weather radar applications.
	www.norman.noaa.gov /publicaffairs/backgrounders/backgrounder_par.html (645 words)

	Electronic Scanning and the Phased Array Chapter 7
		All elements are radiating in phase, and the resultant wave front is perpendicular to the axis of the element array.
		When non-reciprocal phase shifters are used, it is necessary to change the phase-shifter setting between transmit and receive to maintain the same phase shift on receive as was used on transmission.
		No matter which of the three possible methods of phase scanning is used in a phased array system, the objective is a relative phase shift of the energy being radiated by each element in the array.
	www.fas.org /man/dod-101/navy/docs/fun/part07.htm (3441 words)

	Limited Scan Phased Array Antenna (Site not responding. Last check: 2007-10-23)
		To reduce the number of phase controls in a constrained feed array architecture, it is common practice to propose using subarrays of several wavelengths in the limited scan plane together with conventional element spacings in the wide angle scan plane.
		Following a phase shifter at each element port, to scan the array, pairs of adjacent columns may be combined in beamformers to provide an aperture amplitude taper for low array factor elevation sidelobes.
		array scan in elevation, the nearest grating lobe is shown in Fig.
	www.ecs.umass.edu /ece/allerton/papers1998/LIMSCAN (2126 words)

	Phased-Array Acoustic Imaging
		Various arrays transmit and receive electromagnetic and acoustic waves according to the requirements of particular applications: radar and sonar, for example.
		Aeroacoustic test applications have used phased arrays of microphones to measure the acoustic source distributions of jets and wind-tunnel models of aircraft.
		They progressed to planar arrays on the ground that are similar in layout to arrays developed by Boeing for wind tunnel testing.
	www.acoustic-imaging.com /array.html (1136 words)

	Phased array element for multiband, multifunction apertures
		This phased array antenna can be used for multiband, multifunction ultra-wide band apertures.
		The resulting phased array antenna can be scanned to form a narrow, high gain beam in any direction within a scan cone.
		It provides more than one octave (67%) of bandwidth with scan, which is very wideband for a phased array; this performance had previously only been possible with much more expensive and thicker arrays.
	www.magneticsciences.com /PhasedArray.html (270 words)

	Guan, Xiang (2005-09-22) Microwave integrated phased array receivers in silicon. ...
		The 16 phases of 19.2-GHz LO signal are generated with a voltage controlled oscillator (VCO) and symmetrically distributed to the phase selectors at all path.
		A differential phase of 52 GHz is generated by the VCO and distributed to all RF paths at the transmitter and receiver.
		The phase shifting is performed at the LO ports of the RF mixers using continuous analog phase shifters.
	etd.caltech.edu /etd/available/etd-09302005-024349 (387 words)

	Calibration of Active Phased Array Antennas Event - The IET (Site not responding. Last check: 2007-10-23)
		The effective operation of a phased array antenna, however, requires that the phase and amplitude applied to the elements is as intended, i.e.
		Since the beam pattern of a phased array antenna is the Fourier Transform of the illumination function and the compressed pulse is the Fourier Transform of the spectrum of the expanded pulse a similar ruggedness can be expected.
		The advantages of active phased array radars could be made available to a much wider range of radars than is possible at present, if the arrays could be made cheaper.
	www.iee.org /oncomms/pn/radar/phased_array.cfm (366 words)

	What are Phased Array Optics?
		Phased Array Optics (PAO) is the as-yet unimplemented idea of creating 2-D arrays of tiny screens programmed to emit light of the specific amplitude and phase necessary to create the illusion of a 3-D image.
		Large Phased Array Optics could simulate the appearance of entire cities, at a level of resolution so fine that the illusion would be preserved even if binoculars were used.
		Because of the technical difficulty of manufacturing so many tiny screens and their corresponding computational hardware, Phased Array Optics are thought of as a futuristic technology, and often mentioned as an application of advanced nanotechnology.
	www.wisegeek.com /what-are-phased-array-optics.htm (477 words)

	Selecting a Phased-Array Mode
		Phasing up from scratch, after changing frequencies or after observing in normal interferometer mode, requires a dwell time of about 3 m on the phase calibrator; VLA slew times plus a maximum of 30 s of VLA setup time should be added to this 3 m.
		Touching up the phasing after a mode VX scan usually requires about 1 or 2 m on the phase calibrator; again, VLA slew and setup times should be added to this calibrator dwell time.
		If these corrupted mode VA phases are held during the subsequent mode VX scan, then the array will be poorly phased while on your VLBI target source, meaning that the VLA's collecting area could be seriously degraded.
	www.vla.nrao.edu /astro/guides/vlbivla/current/node15.html (480 words)

	Times Record News: News
		The system, called phased array radar, is similar to conventional radar but can scan the atmosphere with more detail and at lower elevations, Doug Forsyth, Radar Research and Development Division with NOAA, said.
		Phased array would reduce the scan time of severe weather from six minutes to only one minute, he said.
		The extent of the phased array radar system’s usefulness doesn’t end with weather or aircraft.
	web.timesrecordnews.com /weather_guide/phased_array.htm (427 words)

	New Generation of NDL Phased Array
		The frequency bandwidth of a conventional phased antenna array (PAA) is ultimately limited by the bandwidth of the array elements.
		Specifically, a severe limitation is often caused by the use of phase shifters to scan the beam, which results in beam "squint" in the measured antenna pattern.
		The design, construction and performance of a proof-of-principle two-dimensional phased antenna array based on hybrid nonlinear delay line technology have been investigated in a 4x4 hybrid NDL-based LTSA phased antenna array.
	tempest.das.ucdavis.edu /mmwave/NDL_PAA (905 words)

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