Terra Marine Engineering, Inc.

Inova Gmbh

Ion Geophysical Corporation

Aquatronics, Inc.

William Terry McDavid

William W Bryce

Lawrence Philip Behn

William F Russell

Robert A Baker

Talal A Itani

Embodiments of an apparatus for direct coupling of a capacitive sensor to a delta-sigma converter are described. One apparatus includes a sensor, a charge coupling circuit configured to transfer at least a portion of charge generated by the sensor to an integrating circuit, a first charge feedback circuit configured to feed back charge to the sensor, a second charge feedback circuit configured to feed back charge to the integrating circuit, a comparing circuit configured to detect accumulated charge at the integrating circuit for a current cycle to determine a polarity of charge feedback for a subsequent cycle, and a logic circuit configured to provide a digital output corresponding to the sensed quantity and also configured to provide the polarity of charge feedback determined by the comparing circuit to the first charge feedback circuit and also to the second charge feedback circuit.

Direct coupling of a capacitive sensor to a delta-sigma converter

Methods, systems, and devices for conducting a seismic survey. The system includes a seismic sensor supplying a seismic signal; sampling circuitry configured to convert the signal to a sequence of samples, each sample represented by a bit string; a data communication device configured to transmit compressed seismic data; a recording computer configured to receive compressed seismic data; at least one processor with a computer memory accessible thereto, the at least one processor configured to: create a sample block by storing at least a portion of the sequence of samples in memory units in the computer memory, wherein each sample is stored in a corresponding memory unit; and compress data contained in the sample block by encoding all bits of a particular bit number from the memory units of the sample block in sequence to produce compressed seismic data.

Efficient seismic file transmission

Methods, systems, and devices for conducting a seismic survey. The system includes at least one seismic sensor configured to supply a signal responsive to reflections of acoustic energy from an earth surface; and at least one processor configured to: mitigate sensor offset from a sequence of samples representative of the signal by filtering the sequence of samples using a symmetrical-in-time finite impulse response (FIR) filter. The FIR filter may approximate a sinc-in-frequency filter. The at least one processor may be configured to process the sequence of samples using a plurality of filter stages that are rectangular in time. The length of one filter stage of the plurality of filter stages may be different than the length of another filter stage of the plurality of filter stages.

Removing offset from seismic signals

A modulated carrier is received on a node (10) and then the I- and the Q-channels extracted with a local carrier clock (16) that is free-running relative to the modulated carrier. The I- and the Q-channels are then input to a digital signal processor (26) wherein a composite phase signal is generated representing the phase difference between the modulated carrier and the local carrier clock (16). The composite phase is output from a look-up table in an EPROM (30) and then the free-running phase the local carrier clock (16) and the modulated carrier is discriminated from the composite phase. The free-running phase is then subtracted from the composite phase to yield the phase modulation on the carrier.

Carrier and data recovery and demodulation system

A phase modulation system includes a phase mapping circuit (218) for mapping binary data into a plurality of discrete phase values in accordance with a predetermined phase modulation scheme. The discrete phase values are then filtered in the phase domain by a filter (220) to provide a filtered output. This filtered output is then digitized and input to a numerically controlled oscillator for phase modulating a carrier.

Phase modulated system with phase domain filtering

A seismic telemetry system with automatic power leveling is comprised of a command station (10) and a plurality of remote data acquisition units (14). Each of the DAU's (14) includes an antenna (18) for receiving commands and transmitting data and is connected to a T/R switch (34). Commands are received by command receiver (48) and entered into a system control (50). A power detect circuit (52) is provided for measuring signal strength of the received carrier and this information is compared to an internal reference in the system control (50) and the power output level of the transmitter (56) is adjusted. A transmit power detect circuit (60) is provided for measuring the actual power output by the transmitter (56). This measured power level is compared in the system control (50) with the internal references to determine if the actual power output is equal to the expected power output. If not, an offset is provided to adjust for any discrepancies. The command station (10) receives data from the DAU (14 ) by a data receiver (36). The power of the receive signal is detected by a power detect circuit (42). This information is input to a system control (40) for comparison with an internal reference. If the power detected by the detect circuit (42) is outside of predetermined constraints, an offset is generated and transmitted as a command by a command transmitter (44) back to the select DAU (14) to provide an additional amount of offset to compensate for actual variations in the transmission of the data.

Power leveling telemetry system

A seismic data processing system utilizes vibration type shock waves which are delivered by a reactive mass (52) acting in conjunction with a base plate (50) to output low frequency shock waves to the earth. The force signals for the reactive mass (52) and (50) are measured and input to a transmitter (42) for transmission to a receiver (48) at a control center (28) which also receives resultant measured data. The measured force signal is input to a data correlator (74) as a model signal and correlated with the resultant data to provide processed data out.

Vibrator seismic data correlation system

A symbol generator is provided for generating a filtered analog waveform for use in phase modulating a carrier. A memory (30) is provided for storing predetermined waveform segments. The waveform segments are correlated with an input data stream. The data stream is converted to an address for the memory (30) to output a digital value to a D/A converter (122). The output of the D/A converter (122) is comprised of in-phase and quadrature-phase components which are input to a sample and hold circuit for generating the analog signals. The waveform segments are then sequentially assembled and input to a vector modulator (168).

Symbol generator for phase modulated system

The specification discloses a pressure-sensitive transducer including two spaced pressure-sensitive subassemblies having matched parameters and which are electrically coupled together in a manner to minimize the effect of acceleration on the transducer. In one embodiment, each subassembly comprises a pair of piezoelectric crystals attached to opposite sides of a conductive mounting plate. The two plates are supported on opposite sides of an insulated annular spacer ring in a manner to face like poled surfaces of the crystals in the same directions. The crystals are electrically coupled together in parallel by conductors which couple each pair of crystals of a subassembly together and to the mounting plate of the other assembly.

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Richardson, TX, United States of America

William Terry McDavid