Analysis of AC Amplifiers with Ultra-low Corner Frequency by Using Bootstrapping

2021 ◽  
Author(s):  
Dobromir P. Dobrev ◽  
Emad Alnasser ◽  
Tatyana D. Neycheva
Keyword(s):  
Corner Frequency

scholarly journals Optimizing noise characteristics of mode-locked Yb-doped fiber laser using gain-induced RIN-transfer dynamics

2021 ◽  
Vol 9 ◽  
Author(s):  
Jiangshuoxue Han ◽  
Yang Liu ◽  
Zejiang Deng ◽  
Gehui Xie ◽  
Daping Luo ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Phase Noise ◽  
Transfer Functions ◽  
Dopant Concentration ◽  
Corner Frequency ◽  
Dispersion Management ◽  
Noise Characteristics ◽  
Laser Design ◽  
Parameter Dependent ◽  
Low Phase Noise

Abstract Gain-parameter-dependent transfer functions and phase-noise performances in a mode-locked Yb-doped fiber laser are measured in this study. It is discovered that the corner frequency in the amplitude and phase domains is determined by the absorption coefficient of the gain fiber, when the total absorption and other cavity parameters are fixed. This shows that an oscillator using gain fiber with higher dopant concentration accumulates more phase noise. Furthermore, we present net cavity dispersion-dependent transfer functions to verify the effect of dispersion management on the frequency response. We derive a guideline for optimizing mode-locked fiber laser design to achieve low phase noise and timing jitter.

The use of duration as a measure of seismic moment and magnitude

1975 ◽  
Vol 65 (4) ◽  
pp. 899-913
Author(s):  
Robert B. Herrmann
Keyword(s):  
United States ◽  
Linear Relationship ◽  
Linear Dependence ◽  
Seismic Moment ◽  
Instrumental Response ◽  
Limited Range ◽  
Corner Frequency ◽  
Source Spectrum ◽  
Duration Magnitude ◽  
Central United States

Abstract The observed relationship between magnitude and duration is shown to be a result of the particular shape of the signal coda as a function of time. If the envelope of the coda follows a t−q relationship with increasing time, then the magnitude, mτ, based on a duration τ is consequently of the form m τ = q log ⁡ 10 τ + r . A study of the duration-magnitude and duration-moment relationships for a set of central United States earthquakes indicates that the linear relationship between mτ and log10τ is valid only over a limited range. The departure from the simple linear dependence is explained in terms of instrumental response and the shift of the source-spectrum corner frequency with increasing event size.

A theoretical study of the radiation from small strikeslip earthquakes at close distances

1983 ◽  
Vol 73 (1) ◽  
pp. 83-96 ◽  
Author(s):  
Michel Campillo ◽  
Michel Bouchon
Keyword(s):  
Ground Motion ◽  
Epicentral Distance ◽  
Homogeneous Medium ◽  
Source Model ◽  
Strike Slip ◽  
Peak Ground Velocity ◽  
Corner Frequency ◽  
Crack Model ◽  
Sharp Change ◽  
S Wave

abstract We present a study of the seismic radiation of a physically realistic source model—the circular crack model of Madariaga—at close distance range and for vertically heterogeneous crustal structures. We use this model to represent the source of small strike-slip earthquakes. We show that the characteristics of the radiated seismic spectra, like the corner frequency, are strongly affected by the presence of the free surface and by crustal layering, and that they can be considerably different from the ones of the homogeneous-medium far-field solution. The vertical and radial displacement spectra are the most strongly affected. We use this source model to calculate the decay of peak ground velocity with epicentral distance and source depth for small strike-slip earthquakes in California. For distances between 10 and 80 km, the peak horizontal velocity decay is of the form r−1.25 for a 4-km hypocentral depth and r−1.65 for deeper sources. The predominance of supercritically reflected arrivals beyond epicentral distances of 70 to 80 km produces a sharp change in the rate of decay of the ground motion. For most of the cases considered, the peak ground velocity increases between 80 and 100 km. We also show that the S-wave velocity in the source layer is the lower limit of phase velocities associated with significant ground motion.

Two-parameter scaling of source spectra: Love waves from deep-focus Bonin Islands earthquakes

1977 ◽  
Vol 67 (2) ◽  
pp. 285-300
Author(s):  
R. James Brown
Keyword(s):  
Body Wave ◽  
Scaling Law ◽  
Spectral Ratio ◽  
Love Waves ◽  
Corner Frequency ◽  
Spectral Ratios ◽  
Bonin Islands ◽  
Deep Focus ◽  
Two Parameter ◽  
Fault Length

Abstract Starting with the one-parameter scaling law of Aki, a two-parameter expression is developed to model the source factor of the far-field spectrum from a dislocation fault source for both ω−2 and ω−3 high-frequency asymptotic types. Aki's assumption of similarity is relaxed in two respects: it is neither here assumed that wD0 ∞ L2 (L = fault length, w = fault width, D0 = average dislocation) nor that kT = v kL (kT−1 = correlation time, kL−1 = correlation length, v = velocity of rupture propagation), the latter being equivalent to allowing for Brune's fractional stress drop. From this two-parameter model a four-parameter model of spectral ratio is obtained and fitted to observed spectral ratios by computer optimization of the four parameters. Observed spectral ratios have been determined from the Love waves recorded at NORSAR from six deep-focus Bonin Islands earthquakes using a common-path method. From the optimal values of the four parameters, values are determined for corner frequency (f ≈ 0.2 Hz for m 6.0; f ≈ 0.3 Hz for m = 5.3; m = PDE body-wave magnitude), relative fault length, relative seismic moment (and magnitudes), and p, the slope of the corner-frequency locus. Values found for p are all greater than 3 and such p, in combination with an ω−3 scaling law, can yield a reasonable m:M relation, i.e., with no ceiling imposed on m. A slightly better fit is obtained by starting with an ω−3 model than with ω−2.

Retrieval of source-extent parameters and the interpretation of corner frequency

1983 ◽  
Vol 73 (6A) ◽  
pp. 1499-1511
Author(s):  
Paul Silver
Keyword(s):  
Body Wave ◽  
Amplitude Spectrum ◽  
Low Frequency ◽  
P Wave ◽  
Corner Frequency ◽  
S Wave ◽  
Dislocation Source ◽  
Statistical Measures ◽  
Dislocation Models ◽  
Planar Dislocation

Abstract A method is proposed for retrieving source-extent parameters from far-field body-wave data. At low frequency, the normalized P- or S-wave displacement amplitude spectrum can be approximated by |Ω^(r^,ω)| = 1 − τ2(r^)ω2/2 where r^ specifies a point on the focal sphere. For planar dislocation sources, τ2(r^) is linearly related to statistical measures of source dimension, source duration, and directivity. τ2(r^) can be measured as the curvature of |Ω^(r^,ω)| at ω = 0 or the variance of the pulse Ω^(r^,t). The quantity ωc=2τ−1(r^) is contrasted with the traditional corner frequency ω0, defined as the frequency at the intersection of the low- and high-frequency trends of |Ω^(r^,ω)|. For dislocation models without directivity, ωc(P) ≧ ωc(S) for any r^. A mean corner frequency defined by averaging τ2(r^) over the focal sphere, ω¯c=2<τ2(r^)>−1/2, satisfies ωc(P) > ωc(S) for any dislocation source. This behavior is not shared by ω0. It is shown that ω0 is most sensitive to critical times in the rupture history of the source, whereas ωc is determined by the basic parameters of source extent. Evidence is presented that ωc is the corner frequency measured on actual seismograms. Thus, the commonly observed corner frequency shift (P-wave corner greater than the S-wave corner), now viewed as a shift in ωc is simply a result of spatial finiteness and is expected to be a property of any dislocation source. As a result, the shift cannot be used as a criterion for rejecting particular dislocation models.

10 July 1894 Istanbul Earthquake: Comparing Damages and Ground Motion Simulations

2021 ◽  
Author(s):  
Nesrin Yenihayat ◽  
Eser Çaktı ◽  
Karin Şeşetyan
Keyword(s):  
Ground Motion ◽  
Fault Simulation ◽  
Source Parameters ◽  
Historical Earthquakes ◽  
Corner Frequency ◽  
Simulation Approach ◽  
Ground Motion Simulations ◽  
Finite Fault ◽  
Intensity Map ◽  
Observed Damage

<p>One of the major earthquakes that resulted in intense damages in Istanbul and its neighborhoods took place on 10 July 1894. The 1894 earthquake resulted in 474 losses of life and 482 injuries. Around 21,000 dwellings were damaged, which is a number that corresponds to 1/7 of the total dwellings of the city at that time. Without any doubt, the exact loss of life was higher. Because of the censorship, the exact loss numbers remained unknown. There is still no consensus about its magnitude, epicentral location, and rupture of length. Even though the hardness of studying with historical records due to their uncertainties and discrepancies, researchers should enlighten the source parameters of the historical earthquakes to minimize the effect of future disasters especially for the cities located close to the most active fault lines as Istanbul. The main target of this study is to enlighten possible source properties of the 1894 earthquake with the help of observed damage distribution and stochastic ground motion simulations. In this paper, stochastic based ground motion scenarios will be performed for the 10 July 1894 Istanbul earthquake, using a finite fault simulation approach with a dynamic corner frequency and the results will be compared with our intensity map obtained from observed damage distributions. To do this, in the first step, obtained damage information from various sources has been presented, evaluated, and interpreted. Secondly, we prepared an intensity map associated with the 1894 earthquake based on macro-seismic information, and damage analysis and classification. For generating ground motions with a stochastic finite fault simulation approach, the EXSIM 2012 software has been used. Using EXSIM, several scenarios are modeled with different source, path, and site parameters. Initial source properties have been obtained from findings of our previous study on the simulation of the 26 September 2019 Silivri (Istanbul) earthquake with Mw 5.8. With the comparison of spatial distributions of the ground motion intensity parameters to the obtained damage and intensity maps, we estimate the optimum location and source parameters of the 1894 Earthquake.</p>

The relations between the corner frequency, seismic moment and source dynamic parameters derived from the spontaneous rupture of a circular fault

2021 ◽  
Vol 228 (1) ◽  
pp. 134-146
Author(s):  
Jian Wen ◽  
Jiankuan Xu ◽  
Xiaofei Chen
Keyword(s):  
Stress Drop ◽  
Seismic Moment ◽  
Dynamic Models ◽  
Scaling Law ◽  
Boundary Integral ◽  
Corner Frequency ◽  
Dynamic Parameters ◽  
Zone Size ◽  
Dynamic Rupture ◽  
Scaling Relationships

SUMMARY The stress drop is an important dynamic source parameter for understanding the physics of source processes. The estimation of stress drops for moderate and small earthquakes is based on measurements of the corner frequency ${f_c}$, the seismic moment ${M_0}$ and a specific theoretical model of rupture behaviour. To date, several theoretical rupture models have been used. However, different models cause considerable differences in the estimated stress drop, even in an idealized scenario of circular earthquake rupture. Moreover, most of these models are either kinematic or quasi-dynamic models. Compared with previous models, we use the boundary integral equation method to simulate spontaneous dynamic rupture in a homogeneous elastic full space and then investigate the relations between the corner frequency, seismic moment and source dynamic parameters. Spontaneous ruptures include two states: runaway ruptures, in which the rupture does not stop without a barrier, and self-arresting ruptures, in which the rupture can stop itself after nucleation. The scaling relationships between ${f_c}$, ${M_0}$ and the dynamic parameters for runaway ruptures are different from those for self-arresting ruptures. There are obvious boundaries in those scaling relations that distinguish runaway ruptures from self-arresting ruptures. Because the stress drop varies during the rupture and the rupture shape is not circular, Eshelby's analytical solution may be inaccurate for spontaneous dynamic ruptures. For runaway ruptures, the relations between the corner frequency and dynamic parameters coincide with those in the previous kinematic or quasi-dynamic models. For self-arresting ruptures, the scaling relationships are opposite to those for runaway ruptures. Moreover, the relation between ${f_c}$ and ${M_0}$ for a spontaneous dynamic rupture depends on three factors: the dynamic rupture state, the background stress and the nucleation zone size. The scaling between ${f_c}$ and ${M_0}$ is ${f_c} \propto {M_0^{ - n}}$, where n is larger than 0. Earthquakes with the same dimensionless dynamic parameters but different nucleation zone sizes are self-similar and follow a ${f_c} \propto {M_0^{ - 1/3}}$ scaling law. However, if the nucleation zone size does not change, the relation between ${f_c}$ and ${M_0}$ shows a clear departure from self-similarity due to the rupture state or background stress.

A Source Physics Interpretation of Nonself-Similar Double-Corner-Frequency Source Spectral Model JA19_2S

2022 ◽  
Author(s):  
Chen Ji ◽  
Ralph J. Archuleta
Keyword(s):  
Stress Drop ◽  
Wave Speed ◽  
Dynamic Stress ◽  
Corner Frequency ◽  
Rupture Velocity ◽  
Scaling Relation ◽  
Shear Wave Speed ◽  
Dynamic Stress Drop ◽  
Static Stress Drop ◽  
Frequency Source

Abstract We investigate the relation between the kinematic double-corner-frequency source spectral model JA19_2S (Ji and Archuleta, 2020) and static fault geometry scaling relations proposed by Leonard (2010). We find that the nonself-similar low-corner-frequency scaling relation of JA19_2S model can be explained using the fault length scaling relation of Leonard’s model combined with an average rupture velocity ∼70% of shear-wave speed for earthquakes 5.3 < M< 6.9. Earthquakes consistent with both models have magnitude-independent average static stress drop and average dynamic stress drop around 3 MPa. Their scaled energy e˜ is not a constant. The decrease of e˜ with magnitude can be fully explained by the magnitude dependence of the fault aspect ratio. The high-frequency source radiation is generally controlled by seismic moment, static stress drop, and dynamic stress drop but is further modulated by the fault aspect ratio and the relative location of the hypocenter. Based on these two models, the commonly quoted average rupture velocity of 70%–80% of shear-wave speed implies predominantly unilateral rupture.

Signal Wavelength Effect on Overmodulation in Thulium Doped Fiber Amplifiers with Amplified Spontaneous Emission: A Simulink Pedestal

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Mohd Mansoor Khan ◽  
Ramesh Kumar Sonkar
Keyword(s):  
Spontaneous Emission ◽  
Transfer Functions ◽  
Optical Fiber Communication ◽  
Amplified Spontaneous Emission ◽  
Fiber Amplifiers ◽  
Corner Frequency ◽  
Optimum Operating ◽  
Test Bed ◽  
Signal Wavelength ◽  
Communication Signal

AbstractThulium-doped fiber amplifiers (TDFAs) can provide high power optical amplification in the wavelength range of 1,460–1,545 nm (S and near-C bands). They can be employed for dense wavelength division multiplexing (DWDM) in optical fiber communication over a broad range, unlike the Erbium-doped fiber amplifiers (EDFAs), which are active in the C-band only in the conventional “erbium window.” Line service surveillance and management of digital optical information in DWDM TDFA networks can be done by low-frequency amplitude modulation (~100 kHz) of TDFA pump and communication signal, termed as overmodulation. Governing equations for overmodulation gain dynamics in TDFAs using the Bononi and Rusch (1998) model was first derived in a companion paper (2017). The research provides a methodical test bed analysis using MatLab Simulink model with a different outlook in the respective field. The transfer functions for signal-to-signal and signal-to-amplified spontaneous emission were implemented to develop a simulator. An undesirable 30 % increment in the output modulation index at 8 dBm and 1,490 nm were obtained by simulating overmodulation sensitivity at different levels of mean input signal power and signal wavelength respectively at corner frequency. The optimum operating wavelength for TDFAs obtained was 1,490 nm.

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