A digital seismic recording system

1972 ◽  
Vol 62 (6) ◽  
pp. 1641-1647
Author(s):  
D. F. Allsopp ◽  
M. D. Burke ◽  
G. L. Cumming
Keyword(s):  
Seismic Reflection ◽  
Dynamic Range ◽  
Low Noise ◽  
Recording System ◽  
Low Noise Amplifiers ◽  
Deep Crust ◽  
Seismic Recording ◽  
Band Pass ◽  
Quality Recording ◽  
Seismic System

abstract A multi-channel seismic system which records directly on a nine-track synchronous digital tape is described. Low-noise amplifiers with a band-pass of 0.1 to 50 Hz coupled with a 14-bit A to D converter provide the wide-frequency response and dynamic range necessary for high-quality recording of seismic reflection signals from the deep crust.

Gain-ranging analog or digital seismic system

1974 ◽  
Vol 64 (1) ◽  
pp. 103-113 ◽  
Author(s):  
E. R. Kanasewich ◽  
W. P. Siewert ◽  
M. D. Burke ◽  
C. H. McCloughan ◽  
L. Ramsdell
Keyword(s):  
Dynamic Range ◽  
Wide Band ◽  
Low Noise ◽  
Active Filters ◽  
Operating Conditions ◽  
Natural Period ◽  
Analog System ◽  
Effective Dynamic ◽  
Different Levels ◽  
Seismic System

abstract A wide-band, gain-ranging amplifier is described that may be used for recording data with a dynamic range of 60 db in each of three different levels, 12 db apart, so that we achieve an “effective” dynamic ±160-v analog or 84-db digital, within a normal ±10-v analog system. As described, the ranging circuit reduces the gain of the amplifier by a factor of either 4 or 16 whenever the output signal approaches the maximum for the system. The wide-band response is achieved with low-noise operational amplifiers and second-order active filters. Signals with periods greater than 30 sec are amplified by 100 db and those with periods shorter than 1 sec are amplified by 70 db. The system works well in extending the useful output range of a Willmore Mark II seismometer with a natural period of 1.5 sec to over 40 sec under normal field operating conditions. When analog recording, the gain-range switching occurs when the input signal reaches ±8.1-v; when digital recording, the level is ±9.375 v. The period in a divide-by-4- or 16-state is preset by the experimentalist. The gain level is recorded on an extra channel which is also used to record absolute time.

scholarly journals The 1.3mm Full-Stokes Polarization System at CARMA

2015 ◽  
Vol 04 (01n02) ◽  
pp. 1550005 ◽  
Author(s):  
Charles L. H. Hull ◽  
Richard L. Plambeck
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Position Angle ◽  
Low Noise ◽  
Low Noise Amplifiers ◽  
Beam Polarization ◽  
Circular Polarizer ◽  
Angle Measurements ◽  
Millimeter Wavelengths ◽  
And Performance

The CARMA 1.3[Formula: see text]mm polarization system consists of dual-polarization receivers that are sensitive to right- (R) and left-circular (L) polarization, and a spectral-line correlator that measures all four cross polarizations ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) on each of the 105 baselines connecting the 15 telescopes. Each receiver comprises a single feed horn, a waveguide circular polarizer, an orthomode transducer (OMT), two heterodyne mixers, and two low-noise amplifiers (LNAs), all mounted in a cryogenically cooled dewar. Here we review the basics of polarization observations, describe the construction and performance of key receiver components (circular polarizer, OMT, and mixers — but not the correlator), and discuss in detail the calibration of the system, particularly the calibration of the R–L phase offsets and the polarization leakage corrections. The absolute accuracy of polarization position angle measurements was checked by mapping the radial polarization pattern across the disk of Mars. Transferring the Mars calibration to the well-known polarization calibrator 3C286, we find a polarization position angle of [Formula: see text] for 3C286 at 225[Formula: see text]GHz, consistent with other observations at millimeter wavelengths. Finally, we consider what limitations in accuracy are expected due to the signal-to-noise ratio, dynamic range, and primary beam polarization.

scholarly journals New Frontiers of Seismic Surveying in Antarctica: The Mapping of A Thin Layer at the Base of Ice Stream B (Abstract)

1986 ◽  
Vol 8 ◽  
pp. 202-202
Author(s):  
Donald D. Blankenship
Keyword(s):  
Thin Layer ◽  
Seismic Reflection ◽  
Dynamic Range ◽  
Basal Layer ◽  
Recording Equipment ◽  
Power Requirement ◽  
Large Bandwidth ◽  
Ice Stream ◽  
Seismic Recording ◽  
Ice Stream B

The recent availability of high resolution (greater than 250 Hz) seismic recording equipment in the Antarctic field environment has allowed the acoustical mapping of a previously unobserved subglacial phenomenon. This phenomenon is a thin (less than 10 m), yet continuous, layer at the base of Ice Stream B in West Antarctica. Discovery of this layer came during the 1983–84 austral summer in a seismic reflection survey that covered approximately 10 km2 near the Upstream B field camp (83°31’S, 138°05’W). Although analysis of the seismic data is at a preliminary stage, there is the possibility that this feature could be a basal “lubricating” layer; some sort of lubrication is of course necessary to explain the very large horizontal velocities of these ice streams.During the seismic reflection survey on Ice Stream B, a new digital seismic recording system, developed by the Geophysical and Polar Research Center, was used for the first time under field conditions. Resolution of such a thin layer was possible only because of the very large bandwidth (0–600 Hz) and dynamic range (84 dB) of this device; this bandwidth is about twice that possessed by commercially available seismic recorders. In addition, a new level of portability (i.e. a weight of 40 kg and a power requirement of 90 watts), which should make this device usable in virtually any Antarctic field situation, has been achieved by the application of advanced recording technologies. The portability of this digital seismic recorder, when combined with its large bandwidth and dynamic range, should result in the resolution of a whole new class of intra- and subglacial phenomena, of which the thin basal layer of Ice Stream B is the first example.

scholarly journals New Frontiers of Seismic Surveying in Antarctica: The Mapping of A Thin Layer at the Base of Ice Stream B (Abstract)

1986 ◽  
Vol 8 ◽  
pp. 202
Author(s):  
Donald D. Blankenship
Keyword(s):  
Thin Layer ◽  
Seismic Reflection ◽  
Dynamic Range ◽  
Basal Layer ◽  
Recording Equipment ◽  
Power Requirement ◽  
Large Bandwidth ◽  
Ice Stream ◽  
Seismic Recording ◽  
Ice Stream B

The recent availability of high resolution (greater than 250 Hz) seismic recording equipment in the Antarctic field environment has allowed the acoustical mapping of a previously unobserved subglacial phenomenon. This phenomenon is a thin (less than 10 m), yet continuous, layer at the base of Ice Stream B in West Antarctica. Discovery of this layer came during the 1983–84 austral summer in a seismic reflection survey that covered approximately 10 km2 near the Upstream B field camp (83°31’S, 138°05’W). Although analysis of the seismic data is at a preliminary stage, there is the possibility that this feature could be a basal “lubricating” layer; some sort of lubrication is of course necessary to explain the very large horizontal velocities of these ice streams. During the seismic reflection survey on Ice Stream B, a new digital seismic recording system, developed by the Geophysical and Polar Research Center, was used for the first time under field conditions. Resolution of such a thin layer was possible only because of the very large bandwidth (0–600 Hz) and dynamic range (84 dB) of this device; this bandwidth is about twice that possessed by commercially available seismic recorders. In addition, a new level of portability (i.e. a weight of 40 kg and a power requirement of 90 watts), which should make this device usable in virtually any Antarctic field situation, has been achieved by the application of advanced recording technologies. The portability of this digital seismic recorder, when combined with its large bandwidth and dynamic range, should result in the resolution of a whole new class of intra- and subglacial phenomena, of which the thin basal layer of Ice Stream B is the first example.

DETERMINATION OF SEISMIC SYSTEM DISTORTION AND ITS COMPENSATION USING DIGITAL FILTERS

Geophysics ◽  
1968 ◽  
Vol 33 (2) ◽  
pp. 285-301 ◽  
Author(s):  
Russell L. Gray ◽  
J. Hans Leitinger ◽  
John C. Hollister
Keyword(s):  
Digital Filters ◽  
Signal To Noise Ratio ◽  
Recording System ◽  
Computational Technique ◽  
Seismic Recording ◽  
Exploration Tool ◽  
Velocity Impulse ◽  
Complete Amplitude ◽  
Amplitude Compensation ◽  
Seismic System

Distortion is inherent in recording seismic data. Although some distortion serves a useful purpose, distortion of desirable seismic events decreases resolution thereby reducing the effectiveness of the seismograph as an exploration tool. This paper describes an experimental‐computational technique to determine the distortion introduced by a seismic recording system. The technique utilizes a piezoelectric shaketable to obtain suitable input‐output pairs from which the velocity impulse response of the system is computed. Distortion introduced by the system is compensated by digital filters that are designed in the frequency domain. Nearly complete phase compensation is achieved by designing filters with phase characteristics that closely approximate the negative phase characteristics of the seismic system. Complete amplitude compensation is intentionally averted because of practical considerations. The degree of amplitude compensation deemed feasible is controlled by the relative frequency content of signal and noise. Synthetic examples which simulate field data indicate that approximate compensation filters are effective in removing much of the signal distortion introduced by the seismic recording system without decreasing the signal‐to‐noise ratio.

scholarly journals NRAO 43-m telescope operation at 170-1700 MHz: a Bi-Static Radar Collaboration

2006 ◽  
Vol 2 (14) ◽  
pp. 367-367
Author(s):  
Glen Langston
Keyword(s):  
Dynamic Range ◽  
Wide Band ◽  
High Dynamic Range ◽  
Low Noise ◽  
Low Noise Amplifiers ◽  
Ionospheric Turbulence ◽  
Radio Stations ◽  
University Of Technology ◽  
Fm Radio ◽  
High Dynamic

AbstractThe NRAO 43m telescope has been refurbished and begun regular observations in the frequency range 170 - 1700 MHz. The 43 m operations support a Bi-Static Radar Collaboration to measure the Earth's ionospheric turbulence. Researchers from Chalmers University of Technology in Sweden have designed and built a unique design wide-band feed, 150 - 1700 MHz. Lincoln Laboratories/MIT has packaged the feed with room temperature low noise amplifiers. Lincoln Laboratories has installed a high-dynamic range RF system together with a wide-band sampler system. The NRAO operates the 43 m telescope according to schedules authored by Lincoln Laboratories. Currently the 43 m telescope is tracking spacecraft 48 hr a week. The tracking antenna operation is completely automated. A group at MIT/Haystack have installed a second radar experiment at the 43 m as well as an array of 6 ‘discone’ antennas. Their experiment is testing the use of reflected FM radio stations as probes of the ionosphere.

ИССЛЕДОВАНИЕ НИТРИД-ГАЛЛИЕВЫХ МАЛОШУМЯЩИХ УСИЛИТЕЛЕЙ ПРИ КРИОГЕННЫХ ТЕМПЕРАТУРАХ

2020 ◽  
Vol 96 (3s) ◽  
pp. 347-352
Author(s):  
Д.Г. Алипа ◽  
В.В. Краснов ◽  
В.М. Минненбаев ◽  
А.В. Редька ◽  
Ю.В. Федоров
Keyword(s):  
Remote Sensing ◽  
Gallium Nitride ◽  
Millimeter Wave ◽  
Low Noise ◽  
Low Noise Amplifiers ◽  
Cryogenic Temperatures ◽  
Space Systems ◽  
Earth Remote Sensing ◽  
Hydrogen Level

В статье представлены результаты исследования возможности применения при криогенных температурах водородного уровня дискретных приборов и монолитных схем на основе нитрида галлия в составе малошумящих усилителей сантиметрового и миллиметрового диапазона длин волн для приемных устройств систем дистанционного зондирования Земли из космоса и в составе криогенных комплексов наблюдения космического пространства. The article presents the results of the research on the possibility of using discrete devices and gallium nitride monolithic circuits at the cryogenic temperatures of hydrogen level as part of low-noise amplifiers of centimeter and millimeter-wave bands used in receivers of Earth remote sensing space systems and in cryogenic systems for space observation.

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