Abstract: Techniques are disclosed relating to control of seismic sources such as marine vibrators. According to some embodiments, iterative learning control (ILC) systems may be used to control such seismic sources. According to some embodiments, local sensor(s) placed in, on, or near a seismic source and/or remote sensors placed in the far-field region may be used to determine a transfer function for the seismic source for such ILC control. A sensor is configured to measure the acoustic output of the marine vibrator along with signal pulses from at least one impulsive seismic signal source. The ILC is disabled when it is determined that the impulsive seismic is active based on the sensor measurements.

Abstract: Techniques are disclosed relating to control of seismic sources such as marine vibrators. According to some embodiments, iterative learning control (ILC) systems may be used to control such seismic sources. According to some embodiments, local sensor(s) placed in, on, or near a seismic source and/or remote sensors placed in the far-field region may be used to determine a transfer function for the seismic source for such ILC control.

Abstract: An example method may include transmitting a first acoustic signal from a downhole tool using a transmitter gain in a transmitter circuit. A first echo signal associated with the first acoustic signal may be received at the downhole tool using a receiver gain in a receiver circuit. At least one of the transmitter gain and the receiver gain may be adjusted based, at least in part, on the received first echo signal and at least one previously received echo signal.

Abstract: Variable feedback architecture and control techniques for variable gain amplifiers (VGAs) concurrently maintain, across a wide range of VGA gain settings, minimal input and output impedance variations, a low noise figure, low rates of change in noise figure, high signal-to-noise ratio (SNR), high quality of service (QoS), low distortion, high and relatively constant output third order intercept point (i.e., IP3 or TOI). Variable feedback counteracts impedance variations caused by gain variations. Compared to conventional high performance VGAs, noise figure is lower (e.g. 3 dB lower at maximum gain and 12 dB lower at minimum gain) and relatively constant, IP3 is higher and relatively constant, small signal third order intermodulation signal (IM3) tone slope is relatively constant and input and output impedances are relatively constant. As gain decreases, the noise figure advantage is nearly dB per dB compared to conventional high performance VGAs.

Abstract: In a pulse-echo ranging system an energy pulse is transmitted to a target, echo pulses are received and converted into an echo signal that is processed to identify an echo from the target and to determine the distance from the propagation time of the identified echo, where the advanced stage of the processing is performed digitally. Instead of storing and processing the echo signal, the first derivative of the whole echo signal is stored in digital form and then processed to allow for storing as large a number of samples possible in a limited memory without reducing the resolution and without complicating the processing.

Abstract: A method for designing a sound waveguide surface is described. The method includes the steps of forming a parametric model of the sound waveguide surface where the parametric model has at least one input parameter and then simulating a sound field that is formed by the sound waveguide surface. A frequency dependent spatial distribution measure is then determined for the sound field associated with the sound waveguide surface and the at least one input parameter is varied to change the sound waveguide surface to adjust the value of the frequency dependent spatial distribution measure.

Abstract: An adaptive equalizer adapted to compensate a signal transmitted by a channel is provided. The adaptive equalizer includes a signal booster, an amplifier unit and an adaptive control loop. The signal booster receives the signal, adjusts gain for the signal, and outputs the signal which has been adjusted. The amplifier unit is coupled to the signal booster, amplifies the signal and outputs it to the next stage. The adaptive control loop is coupled to the signal booster, detects a ratio of a maximum value and a minimum value of the signal package, and outputs an adjusting signal to adjust the gain of the signal booster to change the maximum value or the minimum value, so that the ratio of the maximum value and the minimum value is not less than a specific value. Furthermore, an adaptive equalizing method is also provided.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may include exciting a plurality of signal source pairs having a substantially equal and non-zero acoustic signature amplitude difference in a frequency domain to provide acoustic signal data, and acquiring the acoustic signal data along a selected azimuth. The plurality of signal source pairs may comprise acoustic bender plates, perhaps included in the outer wall of a downhole tool.

Abstract: An amplifier circuit to amplify a sequence of echoes and to generate a corresponding sequence of amplified signals. In an embodiment, the amplifier includes an operational amplifier, with variable input and feedback resistances such that the ratio of the two resistances can be controlled. A gain control block controls the ratio in a time dependent manner to obtain desired gain factors for each of the echoes. The gain factors can be pre-computed such that all the echoes are gained to the same level in case of an ultra-sound system.

Abstract: A method of processing seismic data comprises processing data representative of the acceleration wavefield so as to obtain information about the earth's subsurface direct from the seismic data representative of the acceleration wavefield. In conventional techniques for processing seismic data representative of the acceleration wavefield the data are transformed to the velocity domain at an early stage in the processing. The invention enables the transform step to be eliminated, thereby simplifying the processing and eliminating the risk that the transform might degrade the data. Furthermore, the increased sensitivity at high frequencies of a typical acceleration sensor compensates for the low-pass filter effect of the earth.

Abstract: A hybrid serial/parallel bus interface has a data block demultiplexing device. The data block demultiplexing device has an input configured to receive a data block and demultiplexes the data block into a plurality of nibbles. For each nibble, a parallel to serial converter converts the nibble into serial data. A line transfers each nibble's serial data. A serial to parallel converter converts each nibble's serial data to recover that nibble. A data block reconstruction device combines the recovered nibbles into the data block. The data block is employed by a gain controller. Each nibble has at least two start bits whose states collectively represent both a function and/or destination.

Abstract: A hybrid serial/parallel bus interface has a data block demultiplexing device. The data block demultiplexing device has an input configured to receive a data block and demultiplexes the data block into a plurality of nibbles. For each nibble, a parallel to serial converter converts the nibble into serial data. A line transfers each nibble's serial data. A serial to parallel converter converts each nibble's serial data to recover that nibble. A data block reconstruction device combines the recovered nibbles into the data block. The data block is employed by a gain controller.

Abstract: An improved method for fabricating a three dimensional monolithic memory with increased density. The method includes forming conductors preferably comprising tungsten, then filling and planarizing; above the conductors forming semiconductor elements preferably comprising two diode portions and an antifuse, then filling and planarizing; and continuing to form conductors and semiconductor elements in multiple stories of memories. The arrangement of processing steps and the choice of materials decreases aspect ratio of each memory cell, improving the reliability of gap fill and preventing etch undercut.

Abstract: A gain control circuit for a telephone, the circuit comprising a signal strength calculator for calculating the strength of a signal; a gain controller adapted to modify the strength of the signal in accordance with a predetermined criterion based on the strength of the signal calculated by the signal strength calculator.

Abstract: A method for identifying the boundaries between sequences of rocks laid down in different depositional regimes. The approach used is to search, in well logs or seismic data, for a statistic characteristic of such regimes, and for breaks in that statistic. The preferred statistic used in the method of the present invention is the first moment of the power spectrum of the wavenumber of a suitable physical property as a function of depth. This statistic is calculated rapidly and with excellent depth resolution from the complex-valued autocorrelation function at its zero and unit lag values, respectively, and displayed as a single variable in black-and-white or color. The method of the present invention further includes manipulations that achieve the approximate conversion of the scale (and corresponding display) from its initial dependence on depth to one that is displayed as a function of geologic time.

Abstract: The arrangement in the field of seismic emission-reception system changes as it progrsses along the profile explored, which modifies the respective distances between the source of seismic signals (S) and each of the siesmic receivers (Ri). In order to take account thereof, each of the acquisition boxes (Bi) used in the field for amplifying, digitizing and storing the siesmic signals received during each emission-reception cycle (or possibly a central station) is provided with a processor for determining automatically the gain to be assigned to the various amplifiers from all of the signals acquired and with selection rules taking into account the level of the signals and their evolution observed over several successive emission-reception cycles. The invention has an application in decentralized automatic control of acquisition devices.

Abstract: Balancing of signal amplitudes in recorded seismic data prior to its transformation from its original domain (such as offset-time, or X-T) to a different domain (such as frequency-wave number, or F-K) has been found to cause unwanted repetitive pattern dispersion in the data. This unwanted effect is removed by determining a corrective factor, the ratio of amplitude of the seismic data to its trace envelope, prior to transformation. The data is then transformed into the different domain where meaningful reflection content is enhanced, such as by two-dimensional filtering. The data is then inverse transformed to the original domain. An inverse corrective factor is then applied, restoring the amplitude of the reflection signal component of the data.

Abstract: A rotary ultrasonic transducer logging tool is set forth which has a transmitter connected to a transducer for transmitting pulses periodically, and a rotor with angle sensor connected thereto. One full revolution is divided into a specified number of incremental steps. The output of the receiver is supplied to an automatic gain control amplifier, then to an analog to digital converter. A gain control setting for the AGC amp is included. The AGC setting for the particular corresponding points in a first revolution of the transducer are used to provide settings for the AGC amplifier in the next revolution. A first buffer is used to store the data for the first revolution, a second buffer for the second revolution, and alternately back to the first buffer. These two buffers provide an output signal for a gain control buffer then input to the AGC amplifier. Alternate forms of gain control signal selection are used such as prior gain control settings.

Abstract: In apparatus for investigating earth formations traversed by a borehole, improved methods and apparatus are provided for performing inductive type formation measurements. A transmitter coil of a well logging tool moving through a borehole emits an alternating field into the adjacent earth formation thus inducing eddy currents therein. A voltage in a receiver coil in the tool is sampled at discrete elevations as the tool traverses the borehole and amplified. This voltage is phase detected with respect to the transmitter coil voltage to insure that the measured receiver voltage corresponds to the currents induced in the formation. An average of these voltage measurements is formed. Variations in the magnitude of the average phase-detected voltage are used to discretely control the amplitude of the alternating current induced into the formation.

Abstract: The seismic amplifier includes an amplifying circuit which amplifies an analog signal to provide an amplified analog signal. The amplified analog signal is converted to digital signals. A controlled network connected to the amplifier circuit controls the gain of the amplifier circuit in a manner so that the gain for a current seismic operation, except for an initial seismic operation, is determined during the next previous vibration seismic operation.

Abstract: A geophone amplifier including a low cut filter which provides non-linear amplification of the signal to produce a substantially flat frequency response so as to enhance high frequency signals containing high resolution information. Discrete plug-in modules are used to custom design the parameters of the system to increase the signal-to-noise ratio and provide a signal which is conditioned for transmission to a data collection unit. Low power drain circuitry is used so that the system can be implemented as a portable unit for conditioning the seismic geophone signal prior to transmission over a long distance.

Abstract: A borehole televiewer circuit for compensating for out-of-roundness of a borehole. The circuit comprises an automatic gain control circuit having time constants that allow detection of borehole anomalies while having a fast enough rise time to adjust for the effects of out-of-roundness.

Abstract: In a system for providing maximum display deflection within a preselected scale size for a time-varying imput whose envelope may be monotonically decreasing, or otherwise varying, automatic gain control means produces a multiplication factor by which an input signal is multiplied to provide an output signal for provision to utilization means such as a display. The multiplier signal is produced as a function of an error signal. The output signal is compared to a value indicative of a desired trace size to produce a signal representative of percentage error rather than a difference. The percentage error is subtracted from 100% to provide a gain error signal, a function of which is the multiplier signal. The function may be further generated by sampling the gain error signal over a window length and summing the samples. The integral thus obtained may be utilized as an exponent in the value of the multiplication factor.

Abstract: An improved apparatus and method for calculating automatic gain correction to be applied to seismic samples is disclosed which features apparatus and method for calculation of the average absolute value of a window of samples in the vicinity of the sample being processed, the calculation being performed a first time with the window shifted toward a first side of the sample and a second time with the window shifted toward a second side of the sample, and selecting for use in gain correction the minimum of the two calculated average absolute values, such that high amplitude samples in the vicinity of relatively low amplitude events is precluded from causing unrealistic shadowing around such events.

Abstract: An apparatus for use in transmitting compressed digital voice data includes an analyzer for compressing digitized voice data according to an algorithm which produces a root mean square of the voice data. An analog to digital converter is used to convert analog voice signals to digital data as an input to the analyzer. An AGC circuit controls to analog voice signal to keep it within predetermined limits for digitization, with the AGC setting being determined by the root mean square of the digitized data. The digitized data includes data representative of the root mean square adjusted by the inverse of the change induced by the AGC. A speech synthesizer expands the digitized data at a remote location to convert it back to analog speech signals.

Abstract: A circuit is disclosed for use in an acoustic logging tool incorporating a transmitter sending an acoustic pulse which is received by acoustic receivers. In the preferred and illustrated embodiment hereof, an automatic gain control (AGC) circuit controls the receiver amplification to enable the output range to be limited for input to a digital graphic recorder, typically having a limited number of output signal levels, coordinating with data processing equipment. The AGC times the peak operation to thereby limit the dynamic range.

Abstract: A method for applying automatic gain control to seismic signals is disclosed which features least means squares fitting the average absolute value of the data in windows of a seismic trace to an exponential function, wherein values for the parameters defining the function are derived and applying a gain function using these parameters to the data.

Abstract: The data transmission rate in a cable telemetry system is improved by preconditioning an encoded data signal prior to discriminating and decoding it with a filter/amplifier employing an operational amplifier having a non-inverting input connected to receive the data signal, an inverting input which is grounded through a series connected resistance and capacitance and an output which is feedback connected to said inverting input by a resistance.

Abstract: An amplifier system repeatedly samples the voltage level of an analog signal and selects the gain to be applied to successive samplings of such signal in response to the voltage level of the sampled signals to thereby raise the amplitude of each sampled signal to a desired level.

Abstract: A novel method for electronically determining the gross characteristics of he top layer of the earth's crust at a given location by using a passive seismic transducer as a sensing device for sensing background seismic noise in conjunction with as assembly of generally conventional miniature low power electronic components arranged in a system containing analog and logic circuits with a read-out meter calibrated to represent the detected background noise as seismic resonant frequency. The electronic determination of the crust character is in lieu of various conventional soil refractometry tests which are lengthy time-consuming procedures. The seismic resonant frequency has been found to be representative of the thickness and of the property or character of the crust at that particular geographical location.

Abstract: A floating point formatter for changing fixed point serial digital data, such as that received by a seismic data acquisiton system, is disclosed wherein fixed point serial digital data is received and scaled to remove any bias added by preamplification. The scaled data is shifted a predetermined number of bits and a resulting exponent is calculated. The shifted data signal and corresponding exponent are combined and further scaled to permit stacking the data without exceeding the system capacity.

Abstract: An A/D converter used with an A/D conversion system in which each of input analog signals applied thereto is amplified at a gain selected depending or the level of said each signal and subjected to A/D conversion. The A/D converter is arranged to select a desired one of predetermined gain select modes concerned with the selection of gain of the amplifier. Further, the A/D converter produces a reference analog signal of a level corresponding to the selected gain select mode and compares the input analog signal with the reference analog signal, thereby determining whether or not the gain of the amplifier is to be changed.

Abstract: In apparatus for investigating earth formations traversed by a borehole, improved methods and apparatus are provided for achieving dynamic range control of formation measurements. In one embodiment adapted to formation resistivity measurements, a well logging tool moving through a borehole emits a current into the adjacent earth formation, and a corresponding measurement voltage correlative to the resistivity is sampled at discrete elevations as the tool traverses the borehole. An average of these voltage measurements is formed. When the magnitude of this average exceeds or drops below a predetermined range, the magnitude of the survey voltage is decreased or increased respectively by a discrete amount.

Abstract: A floating point analog-to-digital converter for use in a digital induction logging tool is disclosed. Floating point samples of phase quadrature components of the receiver signal are obtained. Each sample contains a digital word representing the exponent of a floating point number and digital word representing its magnitude. A voltage-to-frequency converter produces an output frequency proportional to the magnitude of the component signal. The resulting frequency signal is counted over a predetermined time inverval. At the completion of each time interval, the count is shifted until a predetermined magnitude is reached. The number of shift pulses required to reach this magnitude represents the exponent. The resulting shifted count represents its magnitude.

Abstract: A wide dynamic range automatic gain ranging amplifier system includes an amplifier which receives an analog input signal and amplifies the received analog input signal in accordance with gain control signals to provide an amplified signal. A network connected to the amplifier also receives the analog input signal and provides the gain control signals corresponding to a desired gain for the amplifier in accordance with the received input signal and also provides gain status signals representative of the gain associated with the amplified signal.

Abstract: Methods and apparatus for calibrating terminated ultrasonic electroacoustic transducers are disclosed. The transducers are excited by a driving signal to emit an ultrasonic acoustic wave, which wave is received either by the same transducer after reflection or by a second transducer to produce an output signal. The driving signal and output signal are supplied to measuring circuitry deriving transdBACKGROUND OF THE INVENTIONThe invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.

Abstract: An improved instantaneous floating point amplifier is provided having a plurality of cascaded amplifier stages, wherein the gain of a given stage of the amplifier is the square of the gain of the immediately succeeding stage of the amplifier. The number of amplifier stages which are required to implement the amplifier is minimized, and the control logic which is required to decide if a given stage is needed to amplify the input signal to a level within preselected limits is simplified. The amplifier has an automatic nulling feature which permits nulling of the amplifier without loss of data.

Abstract: In one exemplar embodiment, an improved method is provided for compensating received propagated seismic signals for the absorption by the earth of all frequencies of a vibrator source signal. The received seismic data is crosscorrelated with the original source signal and a Fourier amplitude spectral analysis obtained. Then an attenuation function is determined by the attenuation exhibited by the spectrum. The quantified attenuation function is then applied as a compensation function to the original source signal to obtain a "weighted" vibrator sweep signal that is then used in crosscorrelating with the received seismic data to compensate for the frequency dependent attenuation in the earth of received propagated seismic data.

Abstract: A geophysical data acquisition system is disclosed having a dynamic range larger than that achievable with typical existing systems. The range of input signals that can be accommodated by a system are limited on the lower end by the noise level of the system and at the upper end by saturation levels of the system. High amplitude input signals can be accommodated by the system if certain unneeded frequency components are filtered off at a sufficiently early point in the signal flow path. In the present invention this desirable filtering is accomplished while maintaining a high gain level in the signal flow path ahead of those components which introduce high noise levels. As a result, the system has an expanded dynamic range and the needed capability to faithfully acquire low amplitude signals.

Abstract: A method for developing an acoustical well log which displays the frequency content of a broad spectrum acoustical signal by discrete windows of the frequency spectrum, the final display being developed concurrently with the taking of the log and being shown with respect to depth. The method employs a spectrum analyzer and, in a single receiver embodiment, a correction circuit for compensating for attenuation introduced by the communication cable from the well-logging sonde to the surface where the recordings are produced. A two receiver embodiment develops and displays the frequency content as amplitude differences at a plurality of frequencies, automatically compensating for cable attenuation.

Abstract: A differential amplifier circuit comprised of two operational amplifiers for use as a differential output and differential input amplifier for any two-terminal impedance transfer function. The input impedance is very low between the two input terminals, yet it is very high between either input terminal and the common or ground terminal, thus giving this amplifier many of the desirable characteristics of a transformer-coupled amplifier. High common mode voltage rejection ratios can be achieved even when moderate differential imbalances exist in the input and feedback networks due to the unique balancing feature of the circuit.

Abstract: A seismic amplifier for use in marine seismic survey work involving the transmission of signals from remote signalling stations over cable pairs to signal processing equipment. These signalling stations are comprised of capacitive transducers. The seismic amplifier of the surveying system includes operational amplifiers electrically interconnected with a feedback circuit comprised of a balanced resistive-reactive network which is a lumped parameter equivalent circuit of the transmission line and capacitive transducer. The lumped parameter equivalent circuit used for feedback provides a flat, zero-phase shift overall response over the cable pair from the transducer to the output of a differential amplifier stage which is connected to the operational amplifier outputs to improve common mode rejection.

Abstract: A method and apparatus for reducing ground current interference with electrical signals representative of seismic signals, said electrical signals passing from at least one geophone to a recording system via an electric circuit including a balancing circuit coupled to ground, whereby a bridge circuit is formed which includes the geophone, the electric circuit and at least part of the recording system, and wherein the balancing circuit comprises two pairs of arms, each pair having at least one arm with variable impedance. Automatic adjustment of the variable impedance occurs based upon electrical information received by a detecting circuit for determining the variation in unbalance of the bridge circuit. Impedance adjustments may be made stepwise or continuously in alternative embodiments of the invention.