Radio spectrum

SETI Search for Extra Terrestrial Intelligence - a survey of the radio spectrum looking for signs of communication from other intelligent life. 

The figures and the theory developed in this work assume the spectra are based on Fermi-Dirac statistics and are related incrementally based on spectral wavelength. In addition, an analysis has been performed to determine if the individual chromophoric spectra show a variation in the ratio of peak wavelength to I/2 amplitude wavelength difference. A similar ratio, based on frequency at the lower frequencies used in the radio spectrum, is considered a quality factor and is designated by Q. The best available estimates of the Q of the visual chromophores of the human eye appear in Table 5.5.10-1 and in the appendix describing the Standard Eye. 

Swings and Rosenfeld, 1937 McKellar, 1940). The discovery in 1963 of the XI8 cm radio spectrum of OH by Weinreb et al. was the first identification of an interstellar molecule by radio astronomy. Thus, up until 1968, only four interstellar molecules were known to exist, leading to the generally accepted conclusion that simple free radicals were the main interstellar molecular constituents in a highly dilute gas (< 1 particle cm-3), subject to ionizing ultraviolet radiation. 

Hydrogen, as an indicator of the presence of water, plays a role in the search for extraterrestrial life. In an October 1992 story about NASA s then newly computerized search for intelligent life in space, Newsweek noted that the ongoing search by the planetary researcher Paul Horowitz was focused on hydrogen s frequency of 1420 megahertz. This simplest and most abundant atom in the universe, Newsweek explained, vibrates at a frequency of 1,420,405,751 cycles a second, a frequency that Horowitz says would make sense as a meeting place in the vast radio spectrum. 8... 

The ultimate accuracy of such a clock depends upon a variety of factors. Theoretically it should be possible to obtain a permanent accuracy of 1 part in 10 billion (io1 ). At present I part in 10 million has been achieved. Such a clock can be used to improve our astronomical time standards being entirely constant and independent of the earth s movement it could be used, for example, to determine if the sidereal day is more constant than the mean solar day, as some authorities believe may be the case. Conversely it may be of great use to the radio-engineer as it could be used to control more rigidly the frequency of the waves emitted from various stations and thus make more efficient use of the available radio spectrum. This is very necessary if overlapping is to be avoided, because the present crowding has imposed severe limitations both nationally and internationally on the expanding use of radio for industry and communications. 

In the United States the National Telecommunications and Information Administration (NTIA) has responsibility for assigning each portion of the radio spectrum (9 kHz to 300 GHz) for different uses. These assignments must be compatible with the rules of the International Telecommunications Union (ITU), to which the United States is bound by treaty. The current assignments are given in a wall chart (Reference 1) and may also be found on the NTIA web site (Reference 2). The list below summarizes the broad features of the spectrum allocation, with particular attention to those sections of scientific interest. The references should be con-... 

This describes at what frequency the tag is designed to operate. As discussed earlier RFID tags can either operate in LF, HF, or UHF range of the radio spectrum. 

Specific gravity—The weight of a material compared to the weight of an equal volume of water. Spectrum— A range of freqnencies within which radiation has some specified characteristic, such as audio-frequency spectrum, ultraviolet spectrum, and radio spectrum. 

Auctions where bidders submit bids on combinations have recently received much attention. See for example Caplice [15], Rothkopf et al. [61], Fujishima et al. [31], and Sandholm [64]. However, such auctions were proposed as early as 1976 [38] for radio spectrum rights. Rassenti et al. [63], a little later, propose such auctions to allocate airport time slots. Increases in computing power have made combinatorial auctions more attractive to implement. 

Paul R. Milgrom. Auction Theory for Privatization, chapter Auctioning the Radio Spectrum. Cambridge University Press, 1995. 

The stepped-FM UWB sensor can detect radio interference by monitoring the phase detector output in passive mode (transmitter power off/receiver on) and is then designed to have some spectrum hole (nonactivated within a portion of the wide radio spectrum) at the transmitter in order to prevent any conflict and to coexist with the other narrow-band wireless systems. Note that the transmit radio consists of independent narrow-band pulses with a different frequency. As such, if provides the flexibility to support... 

Industrial, scientific, and medical bands are reserved portions of the radio spectrum, defined by the ITU Radio Regulations [23], that are employed in body-centric wireless communication applications and, more in general, for other industrial, medical, and scientific applications. The majority of textile antennas developed to date are intended for operation in some of those ISM bands, especially in the 2.45 GHz, by far the most popular for wearable antennas, and 5.8 GHz bands. The first band represents a good trade-off between antenna dimensions (inversely proportional to fiequency) and path loss (increasing with frequency), whereas the second is more convenient when... 

The HF portion of the radio spectrum, from about 3 to 30 MHz, has recently experienced renewed interest Systems operating in this frequency range are capable of worldwide communications without the use of satellites or other types of relay stations. This capabflity can be enjoyed with relatively low-power levels and unsophisticated antennas with consequently relatively low cost. 

Cellular Radio Spectrum Requirements Basic Cellular Architectme Call Processing... 

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