Topic
Attenuation distortion
About: Attenuation distortion is a research topic. Over the lifetime, 580 publications have been published within this topic receiving 7514 citations.
Papers published on a yearly basis
1 / 2
Papers
TL;DR: In this article, a method for estimating seismic attenuation based on frequency shift data is presented, which is applicable in any seismic survey geometry where the signal bandwidth is broad enough and the attenuation is high enough to cause noticeable losses of high frequencies during propagation.
Abstract: We present a method for estimating seismic attenuation based on frequency shift data. In most natural materials, seismic attenuation increases with frequency. The high-frequency components of the seismic signal are attenuated more rapidly than the low-frequency components as waves propagate. As a result, the centroid of the signal's spectrum experiences a downshift during propagation. Under the assumption of a frequency-independent Q model, this downshift is proportional to a path integral through the attenuation distribution and can be used as observed data to reconstruct the attenuation distribution tomographically. The frequency shift method is applicable in any seismic survey geometry where the signal bandwidth is broad enough and the attenuation is high enough to cause noticeable losses of high frequencies during propagation. In comparison to some other methods of estimating attenuation, our frequency shift method is relatively insensitive to geometric spreading, reflection and transmission effects, source and receiver coupling and radiation patterns, and instrument responses. Tests of crosswell attenuation tomography on 1-D and 2-D geological structures are presented.
673 citations
1 Jan 1951
TL;DR: In this article, it was shown that the distortion introduced in a pulse-count-modulation system due to quantization can be minimized by non-uniform spacing of levels, and that minimum distortion is significantly less than distortion resulting from uniform quantization when the crest factor of the signal is greater than four.
Abstract: It is shown that the distortion introduced in a pulse-count-modulation system due to quantization can be minimized by nonuniform spacing of levels. Equations are derived for an arrangement of nonuniform level spacing that produces minimum distortion. It is also shown that minimum distortion is significantly less than distortion resulting from uniform quantization when the crest factor of the signal is greater than four.
269 citations
Patent•
22 Dec 2000TL;DR: In this article, a delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals.
Abstract: A distortion compensating apparatus for compensating for a distortion of a transmission power amplifier. A delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals, and decides the total delay time caused in the transmission power amplifier and a feedback loop on the basis of the phase difference in which the correlation is the maximum. A delay unit delays the transmission signal before a distortion compensation processing by the total delay time, and inputs the delayed signal into a distortion compensating apparatus arithmetic unit, which calculates and stores a distortion compensation coefficient on the basis of the transmission signal and the feedback signal fed back from the output side of the transmission power amplifier. A pre-distortion unit applies a distortion compensation processing to the transmission signal by using the distortion compensation coefficient.
204 citations
Patent•
6 Sep 1990
TL;DR: In this article, the input signal is split into two paths with the primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path.
Abstract: An electronic circuit provides a linear output from an amplitude modulated transmission device such as an amplifier or a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal with distortion equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two paths with the primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. The secondary path generates predistortion which is recombined with the primary signal in proper phase and amplitude for cancelling distortion in the output device. A distortion generator in the secondary path generates adjustable amplitude intermodulation signals. Filtering is used before the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequencies of the fundamental signals. Filtering is used after the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequency of the distortion. Phase of the distortion signal is adjusted to be in proper phase relation with the distortion of the device. Set points of the predistorter may be adjusted automatically. More than one secondary path may be used.
185 citations
TL;DR: In this article, the authors derived expressions for second and third-order distortion using the time-domain form of the field envelope wave equation, and showed that the distortion predicted by these expressions agrees well with numerical simulation and reasonably well with experimental data.
Abstract: Transmission through dispersive and nonlinear optical fibers produces distortion in subcarrier intensity-modulated systems. Analytic expressions for second- and third-order distortion are derived using the time-domain form of the field envelope wave equation. The distortion predicted by these expressions agrees well with numerical simulation and reasonably well with experimental data. Significant composite second-order distortion is predicted in typical 1.55 mu m cable television systems. >
154 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2017 | 10 |
| 2016 | 5 |
| 2015 | 12 |
| 2014 | 19 |
| 2013 | 15 |
| 2012 | 17 |