Power leveling telemetry system

• US 4,868,795 A
• Filed: 12/09/1987
• Issued: 09/19/1989
• Est. Priority Date: 08/05/1985
• Status: Expired due to Term

• Current Assignee: Terra Marine Engineering Incorporated
• Original Assignee: Terra Marine Engineering Incorporated
• Inventors: McDavid, William T., Bryce, William W.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): SWANN, TOD R
• Application Number:
  US07/131,315
• Time in Patent Office: 650 Days
• Field of Search: 367/76, 367/77, 367/65, 367/67, 346/33 C, 340/870.04, 340/870.05, 455/10, 455/69
• US Class Current: 367/77
• CPC Class Codes: G01V 1/223 Radioseismic systems
• CPC Class Codes: H04W 52/04 TPC

Abstract

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.

Claims

1. A seismic telemetry system, comprising:

means for acquiring seismic data at a remote location;

data link means disposed between said remote location and a central location for carrying encoded data transmissions;

data transmission means at said remote station for encoding said seismic data and transmitting said encoded seismic data over said data link means as an encoded seismic data transmission, said data transmission means having a variable output power, the output power level determined by a control signal input;

data receiver means disposed at said central location for receiving said encoded seismic data transmission from said data link means for decoding thereof and generation of decoded seismic data, said data receiver means processing said decoded seismic data;

command transmitter means disposed at said central location for transmitting periodic command transmissions having a predetermined signal level over said data link means to said remote location;

command receiver means disposed at said remote location for receiving said command transmissions and measuring the signal strength thereof, said command receiver means determining the path loss in said data link means by comparing the received signal strength with a predetermined reference level corresponding to said predetermined level of said command transmissions transmitted from said central location;

level storage means for storing an attenuation level at said remote location;

attenuation means at said remote location for generating said attenuation level for storage in said level storage means, said attenuation level representative of the path loss determined by said command receiver means;

power level means at said remote location for generating said control signal as a function of the value of said stored attenuation level to vary the output of said data transmission means to generate an expected power output level such that the signal strength received by said data receiver means at said central location is within a predetermined window, said control signal generated in accordance with predetermined operating parameters of said data transmission means;

detect means for measuring the power output by said data transmission means to said data link means;

compare means for comparing the measured output power from said detect means with said expected power output level generated by said power level means;

means for controlling said power level means to offset said control signal if said measured output power from said data transmission means differs from said expected power output level by a predetermined amount;

receiver detect means disposed at said central location for measuring the signal strength of the received seismic data transmissions;

means for comparing the measured signal strength of said received seismic data transmission with said predetermined window to determine if the signal strength of said received seismic data transmission is outside of said window;

means for generating a command offset signal at said central location having encoded therein the amount of offset necessary to place the signal strength of said received seismic data transmissions in said window; and

means for encoding said command offset signal into said command transmission for transmission to said command receiver means from said central location;

said command receiver means decoding said command offset and controlling said power level means to offset said control signal by said command offset.

2. The telemetry system of claim 1 wherein said detect means detects the direct power output of said data transmission means.

3. The telemetry system of claim 2 wherein said data transmission means comprises:

means for receiving said acquired seismic data and encoding said acquired seismic data into a predetermined format;

a variable power amplifier for receiving said encoded seismic data and outputting said second encoded seismic data at said expected power output level, said expected power output level responsive to said control signal input on a control input, said control sigal determining said expected power output level; and

an attenuator disposed on the output of said variable power amplifier for inserting additional attenuation between said amplifier and said data link means.

4. A seismic telemetry system with power leveling comprising:

a command station for controlling the telemetry system and processing data received thereby, said command station having;

command transmit means for periodically generating a command transmission signal at a predetermined signal strength having command information encoded therein and transmitting said command transmission to the system,

data receive means for receiving seismic data from the system, and

processing means for processing the received data;

a plurality of remote data acquisition stations each having a separate identification code for receiving said periodically generated command transmission add collecting seismic data in response to the command encoded therein, said seismic data encoded into a seismic data transmission, said seismic data transmission for transmission to said command station; and

data link means disposed between said command station and each of said remote stations for carrying said command transmission from said command station to each of said remote stations and carrying said seismic data transmission from each of said remote stations to said command station, said data link means having a transmission loss associated therewith;

said remote stations each having;

command receive means for receiving said command transmission and decoding the command information encoded therein,

signal strength means for measuring the signal strength of said common transmission,

data acquisition means for collecting seismic data,

data transmission means nominally operating at a predetermined output level for encoding said collected data into a seismic data transmission and transmitting said seismic data transmission to said command station over said data link means,

level storage means for storing an attenuation level,

power control means for varying the signal strength output by said data transmission means from said predetermined output level by a value corresponding to the attenuation level stored in said level storage means,

control processor means for comparing the measured signal strength of said command transmission with a predetermined reference value, said predetermined reference value dependent upon said predetermined signal strength of said command transmission at said command station, said control processor means calculating the loss of said data link means between said command station and the associated one of said remote stations, said control processor means generating said attenuation level in accordance with the calculated loss and storing said attenuation level in said level storage means to compensate for the transmission loss of said data link means such that the signal strength of said data transmission received at said command station is within a predetermined signal strength window when said power control means attenuates the signal strength output by said data transmission means;

said command station further comprising;

signal strength detect means for measuring the signal strength of said received seismic data transmission from each of said remote stations,

means for comparing said measured signal strength With a predetermined reference to determine the variation of said measured signal with respect to said predetermined reference, said variation indicating that said received seismic data transmission is in said predetermined window, and

means for calculating an offset when said received signal strength is outside of said predetermined window and generating a command transmission encoded with said offset for transmission to the associated one of said remote stations;

said control processing means of the associated one of said remote stations further comprising means for offsetting said predetermined reference by said command offset, said command offset allowing said command station to control each of said remote stations to vary the output signal strength of said data transmission in response thereto.

5. The seismic telemetry system of claim 4 wherein the loss of said data link means varies as a function of the distance between each of said remote stations and said command station.

6. The seismic telemetry system of claim 4 wherein said command transmission and said seismic data transmissions are modulated RF carriers and said data link means comprises a radio frequency transmission medium.

7. A seismic telemetry system with power leveling, comprising:

a command station for controlling the telemetry system and processing data received thereby, said command station having;

command transmit means for periodically generating a command transmission signal at a predetermined signal strength having command information encoded therein and transmitting said command transmission to the system,

said command information containing attenuation data and associated remote station identification data,

data receive means for receiving seismic data from the system,

signal strength detect means for measuring the signal strength of said received seismic data transmission from each of said remote stations,

means for comparing said measured signal strength with a predetermined reference, said predetermined reference indicating that said received seismic data transmission is in said predetermined window,

means for calculating an offset when said received signal strength is outside of said predetermined window and altering said attenuation data with said offset for transmission to the associated one of said remote stations, and

processing means for processing the received data;

a plurality of remote data acquisition stations each having an associated identification code for receiving said periodically generated command transmission and collecting seismic data in response to the command information encoded therein, said seismic data encoded into a seismic data transmission, said seismic data transmission for transmission to said command stations; and

data link means disposed between said command station and each of said remote stations for carrying said command transmission from said command station to each of said remote stations and carrying said seismic data transmission from each of said remote stations to said command station, said data link means having a transmission loss associated therewith;

said remote stations each having;

command receive means for receiving said command transmission and decoding the command information encoded therein to receive said attenuation data associated with said identification code,

data acquisition means for collecting seismic data,

data transmission means nominally operating at a predetermined output level for encoding said collected data into a seismic data transmission and transmitting said seismic data transmission to said command station over said data link means,

level storage means for storing an attenuation level, said attenuation level nominally equal to a level corresponding to said nominal operating level of said data transmission means,

power control means for varying the signal strength output by said data transmission means from said predetermined output level by a value corresponding to the attenuation level stored in said level storage means, and

control processor means for receiving said attenuation data and offsetting said stored attenuation level in response thereto.

8. The seismic telemetry system of claim 7 wherein said command transmission and said seismic data transmissions are modulated RF carriers and said data link means comprises a radio frequency transmission medium.

9. The seismic telemetry system of claim 7 wherein each of said remote stations further comprise:

signal strength means for measuring the signal strength of said command transmission;

said control processor means comparing the measured signal strength of said command transmission with a predetermined reference value, said predetermined reference value dependent upon said predetermined signal strength of said command transmission at said command station, said control processor means calculating the loss of said data link means between said command station and the associated one of said remote stations, said control processor means generating a new attenuation level in accordance with the calculated loss and storing said new attenuation level in said level storage means at said attenuation level to compensate for the transmission loss of said data link means such that the signal strength of said data transmission received at said command station is within a predetermined signal strength window when said power control means attenuates the signal strength output by said data transmission means.

10. The seismic telemetry system of claim 9 where each of said remote stations further comprises:

power detect means for detecting the actual output signal strength of said data transmission means; and

said control processor means receiving the output of said power detect means and generating an offset to said stored attenuation level in said level means to compensate for variations in said data transmission means that vary from said predetermined output level.