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Topic: Space frequency

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	General time, space and frequency multiplexed acousto-optic correlator - Patent 4641273
		The space and frequency multiplexed, time integrating correlator of claim 2 wherein each said plurality of light detectors is a linear array of light detectors extending in said second direction.
		The space and frequency multiplexed, time integrating correlator of claim 4 wherein one of said plurality of light detectors comprises a number of detectors approximately equal to the bandwidth of each of the frequency multiplexed signals times the aperture time of the acousto-optic cell.
		Introduced herein are space and frequency multiplexed architectures and their extensions that acheve synchronization and demodulation in a much preferable manner.
	www.freepatentsonline.com /4641273.html (4935 words)

	Radio - LearnThis.Info Enclyclopedia (Site not responding. Last check: 2007-10-09)
		A radio wave is created whenever a charged object accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum.
		In frequency modulation, louder sounds at the microphone cause the transmitter frequency to fluctuate farther, the transmitter power stays constant.
		Fidelity is sacrificed to use a smaller range of radio frequencies, usually five kilohertz of deviation (5 thousand cycles per second) for maximum pressure, rather than the 75 used by FM broadcasts and 25 used by TV sound.
	encyclopedia.learnthis.info /r/ra/radio.html (3054 words)

	Speckle reduction techniques (Site not responding. Last check: 2007-10-09)
		A simple frequency compounding method is to transmit a single broad bandwidth pulse and to then select different receive frequency ``sub-bands'' through the application of filters, as shown in Figure 8.5.
		Therefore as we change center frequencies of the compounding bands and calculate their cross correlation, we are calculating the autocorrelation function of a Gaussian.
		For a frequency compounding system, the correlation coefficient between sub-band speckle patterns as a function of the separation of sub-bands is thus the autocorrelation function of a Gaussian.
	dukemil.egr.duke.edu /Ultrasound/k-space/node9.htm (819 words)

	SPACE.com -- Frequency's Wormhole Ideas Unstable
		Frequency relies on the wormhole concept, and a related theory proposing that countless universes exist.
		He calculated that space and time are bound together as a single fabric and that a shortcut, or wormhole, could open between two places in space-time.
		Astrosociology is the study of astrosocial phenomena (social/cultural patterns related to space), a multidisciplinary field open to all scientists and engineers interested in "space and society" issues.
	www.space.com /scienceastronomy/generalscience/freq_time_travel_000428.html (725 words)

	United States Patent Application: 0020165626
		With respect to the treatment of MIMO frequency selective channels, one approach contends the that space-time codes that are designed to achieve a certain diversity order in flat fading channels achieve at least the same diversity order in frequency selective fading channels.
		The apparatus includes means for encoding a signal using space-frequency coding; means for modulating the encoded signal according to a predetermined modulation scheme and an orthogonal frequency division multiplexing scheme; and means for transmitting the modulated signal to a terminal using a plurality of MIMO transceivers.
		The encoded signal is modulated according to a predetermined modulation scheme and an orthogonal frequency division multiplexing scheme, wherein the modulated signal is transmitted a terminal using a plurality of MIMO transceivers.
	www.ece.osu.edu /~helgamal/app6.html (8104 words)

	[No title]
		It means that Spitz's method of using the same prediction filter for double the frequency - half the sampling interval, or triple the frequency - third the sampling interval, are special cases in a continuum of constant spatial sampling interval times temporal frequency.
		The promise of frequency dependent grids for spatial interpolation and signal/noise separation are therefore immense; both quality and economy.
		Interpolate (oversample) the frequency dependent grid signal and noise pyramids to frequency independent grid signal and noise cubes.
	sepwww.stanford.edu /oldsep/shuki/Seminars/fdgrids (736 words)

	Low Frequency Radio Astronomy from Space
		Interferometric space or lunar based arrays for imaging the entire sky below 30 MHz will cover a frequency range which is totally inaccessible or extremely difficult to observe from the ground due to ionospheric absorption and scattering.
		The plasma frequency of the ionosphere is ~15 MHz on the day side of the earth near sunspot maximum and ~10 MHz on the night side near sunspot minimum, making the layer opaque to all lower frequencies.
		The resolution-frequency phase space filled by past or present ground-based arrays and the two LF Radio Astronomy Explorer (RAE) satellites launched in the late '60s and early '70s is shown in the accompanying figure and compared with that which could be explored by a Low Frequency Space Array (LFSA).
	rsd-www.nrl.navy.mil /7213/weiler/lfraspce.html (654 words)

	Radio - Open Encyclopedia (Site not responding. Last check: 2007-10-09)
		Radio waves are a form of electromagnetic radiation, and are created whenever a charged object accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum.
		Electromagnetic radiation travels (propagates) by means of oscillating electric and magnetic fields that pass through the air and the vacuum of space equally well, and does not require a medium of transport.
		By contrast, other types of electromagnetic radiation, with frequencies above the RF range are gamma rays, X-rays, and infrared, ultraviolet and visible light.
	open-encyclopedia.com /Radio (3290 words)

	Linear Pixel Shuffling and Subpattern Searching
		In this experiment, the Frequency Domain algorithm was used to compare against LPS for cases where the Frequency Domain was faster than Space Domain.
		This graph shows LPS, Frequency Domain, and Random Ordering to be pixel size invariant (with LPS being the quickest of the three) compared to Space Domain which is dependent on pattern size.
		Frequency Domain had good results (compared to Space Domain) when the ratio between image and pattern was small.
	www.csh.rit.edu /~adam/LPS/Paper/paper.html (5992 words)

	Ultrasound and k-space (Site not responding. Last check: 2007-10-09)
		As shown in Figure 3.5, a two-element system with two-frequency output is sensitive to six spatial frequencies, with the redundant frequencies having twice the amplitude of the outliers.
		For a broadband transducer, the axial response is often approximated as a Gaussian centered at the transducer's center frequency.
		Hence the weighting of the frequency response reflects the weighting of the sampling of spatial frequencies in the aperture, and is directly related to spatial resolution, as shown in Figure 3.12.
	dukemil.egr.duke.edu /Ultrasound/k-space/node4.htm (2808 words)

	Frequency-shift keying -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-09)
		Frequency-shift keying (FSK) is (Modulation of the frequency of the (radio) carrier wave) frequency modulation in which the modulating (Any communication that encodes a message) signal shifts the (Production of a certain amount) output frequency between predetermined values.
		Note 1: Usually, the instantaneous frequency is shifted between two discrete values termed the " (additional info and facts about mark frequency) mark frequency" and " (additional info and facts about space frequency) space frequency".
		Note 2: (additional info and facts about Coherent) Coherent forms of FSK exist in which there is no (Any distinct time period in a sequence of events) phase discontinuity in the output signal.
	www.absoluteastronomy.com /encyclopedia/f/fr/frequency-shift_keying.htm (167 words)

	[No title]
		NASA explained that signals received on Earth from spacecraft in deep space are extremely weak, and thus are highly susceptible to interference of all kinds.
		But, NASA stated, its earth stations can not be shielded from airborne radio sources operating on frequencies within the sub-band 31.8-32.3 GHz, because the potential interfering signals may emanate from the same general direction as the desired deep space signals.
		Welch believes this is keeping in the spirit of the Commercial Space Act of 1998 and other congressional efforts that aim to ensure the success of commercial space development.
	www.fcc.gov /Bureaus/Engineering_Technology/Orders/2000/fcc00353.txt (1963 words)

	Wireless Communications: Modeling Random Fading Channels (Site not responding. Last check: 2007-10-09)
		A one-dimensional frequency autocorrelation is calculated from the joint time-frequency autocorrelation by setting Δt equal to 0.
		One-dimensional spatial or frequency autocorrelations may be calculated by zeroing out Δf or Δr respectively in the joint autocorrelation.
		Likewise, the complete autocorrelation of the stochastic channel is shown to be the three-domain Fourier transform pair of the complete PSD by wrapping around from the top edge of Figure 3.4 to the bottom edge.
	www.informit.com /articles/article.asp?p=169488&seqNum=3 (1232 words)

	Space frequency listing 8-50 MHz
		Used to be registered as a frequency for space use by the ITU.
		Geoff Perry and Dick Flagg heard "Rubin" on this frequency on 12 oct 1964.
		Later such transmissions were frequently heard by several observers on 19.150 and 19.300 MHz.
	www.svengrahn.pp.se /trackind/freqlist/SpaceFreq.htm (361 words)

	Radio
		When a radio wave passes a wire, it induces a moving electric charge (voltage) that can be transformed into audio or other signals that carry information.
		The next advance was continuous wave telegraphy, or CW, in which a pure radio frequency, produced by a vacuum tube electronic oscillator was switched on and off by a key.
		A receiver with a local oscillator would "heterodyne" with the pure radio frequency, creating a whistle-like audio tone.
	www.brainyencyclopedia.com /encyclopedia/r/ra/radio.html (3085 words)

	[No title]
		Frequently referred to as "810-5" this document provides technical design information about DSN stations and their telecommunications interfaces with flight projects.
		The Space Frequency Coordination Group (SFCG) has reached agreement among its members that space science missions utilizing the Space Research service and operating in the 2 and 8 GHz frequency bands should employ bandwidth efficient modulation (see SFCG Handbook).
		Advances in such diverse subjects as: space communications, radio navigation, radio science, ground-based radio and radar astronomy, and standards development are reported.
	deepspace.jpl.nasa.gov /advmiss (1575 words)

	Spacecraft operations Portal - MissionOperation - About Frequency Management
		The office also supports the development of an ESA-wide frequency management policy, supports projects in the selection of frequency bands, modulation/coding, and Earth stations, and prepares ITU forms for spacecraft frequency notification.
		The office also determines the coordination contours, a prerequisite for international notification of a station, using specialised ITU software that takes into account radio service, horizon masks, and local propagation conditions and is based on a digitised map of the world.
		Given the interdependency between spectrum management, radio frequency, and modulation, the office is also active in standardisation activities at the European Cooperation for Space Standardisation (ECSS)- and the Consultative Committee for Space Data Systems (CCSDS)-level for radio frequency and modulation.
	www.esa.int /spacecraftops/ESOC-Article-fullArticle_idBanner-1082488220917_par-33_1069167511161.html (432 words)

	OhioLINK ETD: Moore, Thomas
		STAP and SFAP algorithms combine spatial and temporal filters to suppress radio frequency interference (RFI) extending the nulling capability of a conventional adaptive array beyond its sensor-limited spatial degrees of freedom.
		As SFAP is implemented in the frequency domain with the weights for each bin determined independently, the total eigenvalue distribution over all bins is accounted for.
		Additionally, a detailed study on normalization of the frequency domain weights is presented with the finding that normalization affects processor flexibility in the nulling of individual frequency bins overwhelmed by unsuppressed interference.
	rave.ohiolink.edu /etdc/view?acc_num=osu1037380239 (371 words)

	Space Adaptive Wavelet Packet Image Compression
		We construct the joint space and frequency library by cascading permutations of these elements.
		We also formulate the space and frequency operations to be commutative, which allows for the full cascade system to be organized into a graph.
		The best joint space and frequency basis is found by pruning the graph which indexes the library such that the embedded graph with least cost is found.
	www.ctr.columbia.edu /~jrsmith/html/pubs/sawpic/space.html (183 words)

	The Hydrogen Maser Clock Project (Site not responding. Last check: 2007-10-09)
		This frequency discriminator uses slowly moving groups of cesium atoms floating in the weightlessness of space that can be interrogated for very long time to obtain a very accurate measurement of the hyperfine separation by which the SI second is defined.
		For this process to work over the long times involved, the interrogating signal must have extremely high frequency stability as the line width of the 9,192,631,770 Hz transition frequency is in the order of tenths of a Hz.
		Work is now in progress to improve the short term (10 to 10,000 sec) stability of the space maser by equipping it with a preamplifier with a lower noise figure and better matched to the output signal from the maser resonator.
	www.cfa.harvard.edu /hmc (1183 words)

	[No title]
		The provisions related to notification of frequency assignments are primarily stipulated in Article 11 of the Radio Regulations except for certain services which affect or which are related to the Plans.
		In case when the associated space station is not recorded into the MIFR, an earth station shall be given an unfavourable finding on the basis that the leading element of a space network is the space station.
		Notices of frequency assignments returned to notifying administrations under the provisions of No.11.36 (unfavaourable under No.11.31) when returned to the Bureau by the notifying administration are not subjected to No.11.46 and will not be accepted as resubmission and will get a new date of receipt.
	www.itu.int /ITU-R/conferences/seminars/jeju-do-2003/docs/06-NotificationRecording.doc (5047 words)

	v-B Space and Frequency Library (Site not responding. Last check: 2007-10-09)
		There are two notions of libraries in the signal expansion: (1) the library of orthonormal basis functions utilized in the full wavelet packet expansion, as discussed earlier, and (2) the library consisting of all the nodes in space and frequency graph.
		Alternatively, since each node represents a region in space and spatial-frequency, a node can also be indexed using a description of the region.
		For example, in the 1-D version of the graph - the joint time-frequency graph, a four-index transform of the 1-D signal is produced.
	www.ctr.columbia.edu /~jrsmith/html/pubs/sawpic/node25.html (220 words)

	Radio at opensource encyclopedia (Site not responding. Last check: 2007-10-09)
		These waves travel (propagate) through the air and the vacuum of space equally well, not requiring a medium of transport.
		In 1963 color television was commercially transmitted, and the first (radio) communication satellite was launched.
		Space drive: Radiation pressure from intense radio waves has been proposed as a propulsion method for interstellar probes.
	wiki.tatet.com /Radio.html (2982 words)

	RTTY BASICS by W7TI
		The lower RF frequency is known as the SPACE frequency and the upper RF frequency is known as the MARK frequency.
		It is customary to refer to the MARK frequency as the frequency you are operating on.
		The reason is that shifting the frequency generates sidebands adjacent to the actual signal and if the sidebands are attenuated, the signal will be degraded.
	www.ok1rr.com /view.php?cisloclanku=2005021501 (2825 words)

	Math 254A (Site not responding. Last check: 2007-10-09)
		A fundamental, and well-known, fact in harmonic analysis is that a function or signal f(t) can be analyzed both in physical space and in frequency space, with the two viewpoints being connected by the Fourier transform.
		It is slightly less well known that one can combine both the physical and frequency variables and analyze a function in time-frequency space, also known as the phase plane.
		Actually, the idea of a phase space representation of sound waves predates that of a physical space or frequency space representation.
	www.math.ucla.edu /~tao/254a.1.01w/blurb.html (339 words)

	Frequency Space Environment Map Rendering
		Our approach is based on spherical frequency space analysis and includes three main contributions.
		This paper introduces a new frequency space paradigm for prefiltering and rendering environment mapped images with general isotropic BRDFs.
		We show that frequency space analysis allows for setting sampling rates accurately, and enables compact representations.
	graphics.stanford.edu /papers/freqenv (493 words)

	[No title]
		The manufacturing technology of space qualified AFSs has vastly improved in the last three decades and the significant improvement in performance is primarily due to the maturity of the electronics industry.
		The superior frequency stability of the AFSs offered two distinct advantages--significantly improve the predictions of satellite orbit determination (ephemerides) by providing stable, low noise signals for ranging, and also eventually extend the time required between control segment updates to orbiting satellites.
		The extremes of temperature that may be encountered in space requires that the thermal and mechanical designs be such that the AFSs maintain excellent frequency stability over a broad range of temperatures.
	www.ieee-uffc.org /fc_history/bhaskar.html (5057 words)

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