Communications: electrical – Wellbore telemetering or control – Using a specific transmission medium
Patent
1994-03-15
1995-12-05
Eldred, J. Woodrow
Communications: electrical
Wellbore telemetering or control
Using a specific transmission medium
3408532, 3408554, 367 76, 367 83, 175 40, G01V 100
Patent
active
054733219
ABSTRACT:
A telemetry system employs a periodic pseudorandom training sequence to effectively initialize an adaptive digital FIR filter-equalizer for optimal communications between a surface modem and downhole measuring equipment, without requiring any changes to the normal logging configuration or any special operator intervention. In a "training mode", an electronic source in a downhole sonde transmits a predetermined training sequence to a surface modem via a cable. The source preferably transmits the training sequence continuously until the surface modem has acclimated itself to the characteristics of the multiconductor cable by adaptively configuring the filter-equalizer, thereby enabling the surface modem to accurately interpret data received from the sonde despite attenuation, noise, or other distortion on the cable. The filter-equalizer adjusts itself in response to an error signal generated by comparing the filter-equalizer's output with a similar training sequence provided by a training generator. After the surface modem is trained, the system operates in an "operational mode," in which the sonde transmits data corresponding to downhole measurements, and the filter-equalizer's error signal is generated by comparing the filter-equalizer's output to a sliced version of the filter-equalizer's output. In this mode, the filter-equalizer continually adjusts itself to most accurately receive and interpret the data.
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Goodman Kenneth R.
Puckett Robert D.
Eldred J. Woodrow
Halliburton Company
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