scholarly journals Computer simulation of low‐frequency electromagnetic data acquisition

Geophysics ◽  
1983 ◽  
Vol 48 (9) ◽  
pp. 1219-1232 ◽  
Author(s):  
William A. San Filipo ◽  
Gerald W. Hohmann
Keyword(s):  
Computer Simulation ◽  
Data Acquisition ◽  
Dynamic Range ◽  
Low Frequency ◽  
Noise Removal ◽  
Digital Data ◽  
Low Frequencies ◽  
Pass Filter ◽  
Natural Field ◽  
Field Noise

Computer simulation of low‐frequency electromagnetic (EM) digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without a remote reference noise removal scheme, it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency‐domain processing and below 0.3 Hz base frequency for time‐domain processing for a typical source‐receiver configuration. A digital high‐pass filter substantially facilitates rejection of natural field noise above these frequencies; however, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low‐frequency limits by one decade, but the remote reference technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range problems. The analysis is also applicable to the induced polarization technique in which similar problems arise at low frequencies in the presence of telluric noise.

Preamplifier With Ultra Low Frequency Cutoff for Infrasonic Condenser Microphone

2012 ◽  
Author(s):  
Rasmus Trock Kinnerup ◽  
Arnold Knott ◽  
Ole Cornelius Thomsen ◽  
Kresten Marbjerg ◽  
Per Rasmussen
Keyword(s):  
Input Impedance ◽  
Dynamic Range ◽  
Cutoff Frequency ◽  
Low Frequency ◽  
Input Resistance ◽  
Bias Current ◽  
Microphone Signal ◽  
Low Frequencies ◽  
Pass Filter ◽  
Condenser Microphone

Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs provide the input bias current. The resulting input impedance of nearly 1 TΩ yields a total lower limiting −3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones.

scholarly journals Ladder-Based Synthesis and Design of Low-Frequency Buffer-Based CMOS Filters

Electronics ◽  
2021 ◽  
Vol 10 (23) ◽  
pp. 2931
Author(s):  
Waldemar Jendernalik ◽  
Jacek Jakusz ◽  
Grzegorz Blakiewicz
Keyword(s):  
Dynamic Range ◽  
Low Voltage ◽  
Supply Voltage ◽  
Low Frequency ◽  
Cmos Technology ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Biomedical Sensors ◽  
Filter Synthesis ◽  
Cascade Method

Buffer-based CMOS filters are maximally simplified circuits containing as few transistors as possible. Their applications, among others, include nano to micro watt biomedical sensors that process physiological signals of frequencies from 0.01 Hz to about 3 kHz. The order of a buffer-based filter is not greater than two. Hence, to obtain higher-order filters, a cascade of second-order filters is constructed. In this paper, a more general method for buffer-based filter synthesis is developed and presented. The method uses RLC ladder prototypes to obtain filters of arbitrary orders. In addition, a set of novel circuit solutions with ultra-low voltage and power are proposed. The introduced circuits were synthesized and simulated using 180-nm CMOS technology of X-FAB. One of the designed circuits is a fourth-order, low-pass filter that features: 100-Hz passband, 0.4-V supply voltage, power consumption of less than 5 nW, and dynamic range above 60 dB. Moreover, the total capacitance of the proposed filter (31 pF) is 25% lower compared to the structure synthesized using a conventional cascade method (40 pF).

scholarly journals Model Calibration of Stochastic Process and Computer Experiment for MVO Analysis of Multi-Low-Frequency Electromagnetic Data

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 605
Author(s):  
Muhammad Naeim Mohd Aris ◽  
Hanita Daud ◽  
Khairul Arifin Mohd Noh ◽  
Sarat Chandra Dass
Keyword(s):  
Stochastic Process ◽  
Computer Simulation ◽  
Model Calibration ◽  
Low Frequency ◽  
Computer Experiment ◽  
Hydrocarbon Exploration ◽  
Computational Time ◽  
Low Frequencies ◽  
Uncertainty Measurement ◽  
Mathematical Equations

An electromagnetic (EM) technique is employed in seabed logging (SBL) to detect offshore hydrocarbon-saturated reservoirs. In risk analysis for hydrocarbon exploration, computer simulation for subsurface modelling is a crucial task. It can be expensive and time-consuming due to its complicated mathematical equations, and only a few realizations of input-output pairs can be generated after a very lengthy computational time. Understanding the unknown functions without any uncertainty measurement could be very challenging as well. We proposed model calibration between a stochastic process and computer experiment for magnitude versus offset (MVO) analysis. Two-dimensional (2D) Gaussian process (GP) models were developed for low-frequencies of 0.0625–0.5 Hz at different hydrocarbon depths to estimate EM responses at untried observations with less time consumption. The calculated error measurements revealed that the estimates were well-matched with the computer simulation technology (CST) outputs. Then, GP was fitted in the MVO plots to provide uncertainty quantification. Based on the confidence intervals, hydrocarbons were difficult to determine especially when their depth was 3000 m from the seabed. The normalized magnitudes for other frequencies also agreed with the resulting predictive variance. Thus, the model resolution for EM data decreases as the hydrocarbon depth increases even though multi-low frequencies were exercised in the SBL application.

scholarly journals Application of a New Combination Algorithm in ELF-EM Processing

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 337
Author(s):  
Fukai Li ◽  
Zhiqiang Yang ◽  
Yehuo Fan ◽  
Yuchun Li ◽  
Guang Li
Keyword(s):  
Electromagnetic Wave ◽  
Measurement Data ◽  
Low Frequency ◽  
New Combination ◽  
Frequency Noise ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Band Noise ◽  
Measurement While Drilling ◽  
Field Noise

With regards to the electromagnetic measurement while drilling (EM-MWD), the extremely-low frequency electromagnetic wave signal (ELF-EM) below 20 Hz is usually used as the carrier of downhole measurement data due to the transmission characteristics of the electromagnetic wave (EM). However, influenced by the low frequency noise of drilling, the ELF-EM signal will be inevitably interfered by field noise, which ultimately impedes decoding. The Fourier band-pass filter can effectively remove out-of-band noise but is incapable of handling in-band noise. Therefore, based on the traditional method, a hybrid algorithm of adaptive Wiener algorithm and correlation detection (AWCD) is designed, so as to enhance the in-band noise processing capability, and the effectiveness of such algorithm is well verified through coding and decoding simulation as well as experimental data. The proposed algorithm, as indicated by theoretical analysis and test data, can effectively solve actual engineering issues, providing methodological references to engineers and technicians.

Frequency spectrum analysis of plant storage tissue during deterioration

1977 ◽  
Vol 55 (18) ◽  
pp. 2437-2438 ◽  
Author(s):  
Terry A. Tattar ◽  
David M. Sylvia
Keyword(s):  
Low Frequency ◽  
Soft Rot ◽  
Healthy Plant ◽  
Storage Tissue ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Pass Filter ◽  
Pass Through ◽  
High Pass ◽  
Plant Storage

Frequency spectra of healthy plant storage tissue indicate that the tissue acts as a high-pass filter that attenuates low frequencies and allows high frequencies to pass through. During progressive deterioration of the tissue from infection of soft-rot bacteria, the frequency spectra indicated a loss in ability of the tissues to filter low frequency signals.

Stable baseline correction of digital strong-motion data

1997 ◽  
Vol 87 (4) ◽  
pp. 932-944 ◽  
Author(s):  
Hung-Chie Chiu
Keyword(s):  
Least Squares ◽  
Linear Trend ◽  
Low Frequency ◽  
Strong Motion ◽  
Digital Data ◽  
Pass Filter ◽  
Strong Motion Data ◽  
Motion Data ◽  
Initial Values ◽  
Least Squares Fit

Abstract Most baseline errors of analog strong-motion data still exist in highresolution data. In this study, we identify the major baseline errors of digital strong-motion data and propose a three-step algorithm to correct these errors. The major baseline errors found in these digital data consist of constant drift in the acceleration, low-frequency instrument noise, low-frequency background noise, the small initial values for acceleration and velocity, and manipulation errors. This threestep algorithm includes fitting the baseline of acceleration by the least squares, applying a high-pass filter in acceleration, and subtracting the initial values in velocity. A least-squares fit of a straight line before filtering can effectively remove the baseline drift in acceleration. Then, the filtering removes the linear trend and other low-frequency errors that exist in the acceleration. Finally, the subtracting of the initial velocity removes the linear trend of displacement. Among these three steps, only the filtering in the second step may introduce a side effect. Compared to the Volume II routine developed by Trifunac and Lee (1973), this three-step processing significantly reduces computational efforts and side effects resulting from unnecessary manipulation of data. This algorithm has been successfully tested on several types of digital strong-motion data. Several independent validations show that the proposed algorithm is stable.

Data Acquisition System Connect to CMG-3T Low-Frequency Seismic Pendulum

2013 ◽  
Vol 734-737 ◽  
pp. 2945-2948
Author(s):  
Ting Ting Liu ◽  
Yong Wu ◽  
Jun Lin
Keyword(s):  
Data Acquisition ◽  
Seismic Waves ◽  
Low Frequency ◽  
Data Acquisition System ◽  
Low Noise ◽  
Acquisition System ◽  
Power Module ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass

Aiming at the low-frequency performance of the lowfrequency seismic pendulum CMG -3T, we design a data acquisition system can acquire the low-frequency seismic waves, at the same time we accomplish the process of adjusting the CMG-3T. This paper gives designing scheme include the low noise design of the power module, the design of the connector to RS232 which can send command to adjusting the mass of CMG-3T,the design of voltage attenuation network and no-source low-pass filter network of data acquisition system, the last is the design of software for adjusting the CMG-3T.

scholarly journals AN INSTRUMENTATION SYSTEM FOR WAVE MEASUREMENTS, RECORDING AND ANALYSIS

2011 ◽  
Vol 1 (7) ◽  
pp. 5
Author(s):  
H.G. Farmer ◽  
D.D. Ketchutn
Keyword(s):  
Data Acquisition ◽  
Data Storage ◽  
Dynamic Range ◽  
Digital Data ◽  
Wave Measurements ◽  
Reduction System ◽  
Wave Slope ◽  
Electronic Computers ◽  
Analogue To Digital ◽  
Digital Data Storage

For the instrumentation system to be described, it was required that the system detect the sea surface accurately, be flexible in dynamic range, be able to detect and record at least six wave records simultaneously, be able to record the data at a station remote from the detectors, and be able to convert the data from analogue to digital form for analysis by electronic computers. Two types of wave measurements were required, the wave elevation and the wave slope. Resistance wire detectors were used and the theory of their operation is presented. The data acquisition and reduction system utilize recently developed telemetry techniques. Raw data storage is on magnetic tape using an inexpensive tape recorder and the digital data storage utilizes punched paper tape. The resistance wires have proven most satisfactory for small and large waves. The data acquisition and reduction system is sufficiently general that it should have application to other type investigations.

scholarly journals Μελέτη, ανάλυση και βελτίωση της λειτουργίας αερομεταφερόμενου ραντάρ συνθετικής απεικόνισης (SAR) χαμηλών συχνοτήτων

2002 ◽  
Author(s):  
Αθανάσιος Πότσης
Keyword(s):  
Data Processing ◽  
High Performance ◽  
Dynamic Range ◽  
Low Frequency ◽  
Low Noise ◽  
Electromagnetic Spectrum ◽  
System Operation ◽  
Low Frequencies ◽  
Technological Advances ◽  
Sar Data

Because of its high resolution, frequency scattering properties and indifference to day/night or cloud cover, Synthetic Aperture Radar (SAR) has become into vogue in the last years. The field of SAR remote sensing has changed dramatically with the operational introduction of new high performance signal processing techniques and new operational modes, like the polarimetry in 1980’s and the interferometry in 1990’s. Additionally, technological advances in antenna design, low noise amplifiers, band-pass filters, digital receiver technology and high frequency digital sampling devises, increase the availability and the performance of airborne as well as spaceborne SAR sensors. All these technological advances result to real time SAR system operation and in most of the frequency bands of the electromagnetic spectrum. These advanced hardware components combined with the new radar techniques result to large variety of operational and research applications. In several of the new coming applications there is the need for a SAR system to penetrate vegetation and foliage. As a result of this, a new class of SAR systems, using low frequencies, has emerged. The combination of low frequency with high bandwidth allows a variety of new military as well as civilian applications. In the frame of this thesis, several hardware and software modifications made in the E-SAR P-Band system operated by DLR aiming the improvement of the collected and processed data quality is described. The basic P-Band inherent problems like the low Signal-To-Noise-Ratio (SNR), the presence of Radio Frequency Interferences (RFI) as well as the high dynamic range of the backscattered signal are addressed. A new mode of operation called “Listen Only” (LO) channel mode gave us the unique opportunity to study and analyze the special characteristics of the interfering signals and the nature of the low frequency backscattered signal. Based on this analysis new RFI suppression algorithms have been developed and the system operation parameters have been set to the correct value resulting to high quality collected data. The effect of RFI signals in fully polarimetric SAR data processing and applications are analyzed in detail. One of the principal items of this thesis is the development of a new robust sub-aperture algorithm for improved Motion Compensation (MoCo) in wide azimuth beam SAR data processing. The new algorithm is incorporated to the Extended Chirp Scaling SAR data processing algorithm. The improved MoCo algorithm results to focused images with high SNR, contrast, higher resolution and better geometric correctness. The performance and the correction accuracy of the proposed algorithms are analyzed by using mainly real data collected by the E-SAR system of DLR.

Sign in / Sign up

Export Citation Format

Share Document