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Superheterodyne

Microwave spectroscopy is used for studyiag free radicals and ia gas analysis (30). Much laboratory work has been devoted to molecules of astrophysical iaterest (31). The technique is highly sensitive 10 mole may suffice for a spectmm. At microwave resolution, frequencies are so specific that a single line can unambiguously identify a component of a gas mixture. Tabulations of microwave transitions are available (32,33). Remote atmospheric sensing (34) is illustrated by the analysis of trace CIO, O, HO2, HCN, and N2O at the part per trillion level ia the stratosphere, usiag a ground-based millimeter-wave superheterodyne receiver at 260—280 GH2 (35). [Pg.314]

The most common application of MMW systems to security needs is the MMW radiometric imager. Systems of this type are very useful because of their ability to detect a variety of concealed weapons hidden by clothing. Millivision Technologies of South Deerfield, MA has been a leader in this field by developing a family of imagers that operate in the 94 GHz atmospheric window and that use a superheterodyne receiver... [Pg.256]

In terms of antique radio technology, this radiometer with an RF amplifier leading to a square-law device is a tuned RF receiver which was the state-of-the art in 1929. The modem superheterodyne circuit for radio receivers with ampflication and filtering at an intermediate frequency (IF) was used by the COBE DMR, but the primary advantage of a superheterodyne receiver over a... [Pg.156]

In heterodyne detection, this last term of frequency (ojs — cor) is detected (with its phase), while the other terms are filtered out. Heterodyne detection of radio waves uses superheterodyne receivers for light waves, heterodyne detection is really interferometry. [Pg.645]

An unusual example of a microwave spectrometer which uses superheterodyne detection and molecular modulation is a tunable-cavity spectrometer designed and built by Radford [13]. Microwave cavities were described in chapter 9, where they form the heart of a microwave magnetic resonance spectrometer. Compared with... [Pg.702]

Superherodyne spectrometers are now not common in laboratory microwave experiments, but superheterodyne detection plays a major role in radio astronomy, as we shall see later. The reasons are obvious one cannot modulate the energy levels of extraterrestrial molecules, and a radio telescope collects radiant energy at all frequencies simultaneously. One does not have a primary monochromatic source of radiation, as in laboratory experiments. [Pg.703]

Figure 10.24. The principal elements of a radio telescope employing superheterodyne detection for recording frequency-discrete line emissions or absorptions [34]. Figure 10.24. The principal elements of a radio telescope employing superheterodyne detection for recording frequency-discrete line emissions or absorptions [34].
Walter Haus Schottky (1886-1976) received his doctorate in physics under Max Planck from the Humboldt University in Berlin in 1912. Although his thesis was on the special theory of relativity, Schottky spent his life s work in the area of semiconductor physics. He alternated between industrial and academic positions in Germany for several years. He was with Siemens AG until 1919 and the University of Wurzburg from 1920 to 1923. From 1923 to 1927, Schottky was professor of theoretical physics at the University of Rostock. He rejoined Siemens in 1927, where he finished out his career. Schottky s inventions include the ribbon microphone, the superheterodyne radio receiver, and the tetrode vacuum tube. In 1929, he published Thermodynamik, a book on the thermodynamics of solids. Schottky and Wagner studied the statistical thermodynamics of point defect formation. The cation/anion vacancy pair in ionic solids is named the Schottky defect. In 1938, he produced a barrier layer theory to explain the rectifying behavior of metal-semiconductor contacts. Metal-semiconductor diodes are now called Schottky barrier diodes. [Pg.157]

In order to avoid this undesirable situation, the liquids have to be purified thoroughly when using the above methods thar spedfic electric conductivity a should not be more than 10 S m . For the study of liquids of relatively high electric conductivity, Malecki propos a pulsed device (superheterodyne receiver with fi-equency modulation) where... [Pg.375]

K. at a frequency of approximately 9.0 Gc/sec. with a superheterodyne spectrometer. Optical measurements were made at room temperature and 77°K. with a Cary Model No. 14 spectrometer and a Jarrell-Ash F-6 spectrometer using photographic plates. [Pg.205]

Where clock-radios (figure 30) are employed, a variety of significant debris may be discovered. The bulk of all radio enclosures are manufactured cither from wood or plastics and these would, therefore, disintegrate in a fire of any magnitude. Most of these radios arc built on a rather heavy steel or aluminum chassis, and various components are often riveted to this metal base. A normal superheterodyne receiver will probably include a double-section variable capacitor having a radier heavy mounting. Carbon resistors or certain metal-encased capacitors may come through the fire reasonably intact. Parts of the clock... [Pg.324]

Hyde, J.S. (1962) Evaluation of an EPR Superheterodyne Spectrometer, Varian Associates, 7th Annual NMR-EPR Workshop. [Pg.147]

Some of the earliest spin-lattice relaxation time measurements were carried out using superheterodyne detection by partial saturation of the magnetic resonance by a microwave pulse, and subsequent monitoring of the transient recovery on an oscilloscope [147], which is essentially a type of saturation recovery measurement... [Pg.220]

Weak spectral absorption is, however, characterised by small changes in a large background power and is therefore ill suited to superheterodyne detection. That background is also detected and overloads the sensitive intermediate frequency amplifier tuned to the beat frequency that is derived from the mixing process. Instead it is customary to modulate the absorption in some way and to observe the modulation on the detected signal rather than the absorption itself... [Pg.62]

The optimum sensitivity of the Fourier transform spectrometer obtained by calculating the signal-to-noise ratio of a pulse Fourier transform spectrometer relative to a conventional absorption spectrometer has also been given. Suppose that a spectral range F has to be investigated in a total time, T. Both experiments will use a superheterodyne detection system with a balanced mixer. The noise is assumed to be white with a power density Pg per spectral unit. The S/N ratio is defined as the ratio of the peak signal amplitude to the rms noise amplitude. [Pg.229]


See other pages where Superheterodyne is mentioned: [Pg.23]    [Pg.921]    [Pg.924]    [Pg.925]    [Pg.89]    [Pg.701]    [Pg.701]    [Pg.703]    [Pg.704]    [Pg.717]    [Pg.718]    [Pg.719]    [Pg.173]    [Pg.305]    [Pg.28]    [Pg.28]    [Pg.60]    [Pg.701]    [Pg.701]    [Pg.703]    [Pg.704]    [Pg.717]    [Pg.718]    [Pg.719]    [Pg.207]    [Pg.208]   
See also in sourсe #XX -- [ Pg.28 , Pg.62 ]




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