US 4,868,795 A · Power leveling telemetry system

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.

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.

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Power leveling telemetry system

Life of this patent

Power leveling telemetry system

Life of this patent

Abstract

Claims10