Power conservation in acoustic telemetry
An acoustic telemetry unit comprising an acoustic receiver for receiving acoustic telemetry signals is disclosed. The acoustic telemetry unit comprises a filter for filtering signals received by the acoustic receiver, a processor for processing signals passed by the filter to recover a data signal, the processor being operable in a sleep mode, and means for waking the processor from the sleep mode in dependence on an output of the filter. An energy storage module may be charged using signals received by the acoustic receiver which are not passed by the filter. The disclosed techniques may help to conserve battery power.
1. An acoustic telemetry unit comprising:
an acoustic receiver arranged to receive acoustic telemetry signals;
a filter arranged to filter signals received by the acoustic receiver;
a processor arranged to process a signal passed by the filter to recover a data signal, the processor being operable in a sleep mode;
a detector arranged to detect the signal passed by the filter; and
a wake-up circuit arranged to wake the processor from the sleep mode when the detector detects the signal passed by the filter.
2. The acoustic telemetry unit according to claim 1 , wherein the filter has a passband corresponding to frequencies used for acoustic communication.
3. The acoustic telemetry unit according to claim 1 , wherein the filter is a passive filter.
4. The acoustic telemetry unit according to claim 3 , wherein the filter is a tuned circuit with a resonant frequency corresponding to frequencies used for acoustic communications.
5. The acoustic telemetry unit according to claim 1 , wherein the detector is arranged to detect when a time integration of the signal passed by the filter is above a predetermined threshold.
6. The acoustic telemetry unit according to claim 1 , wherein the detector comprises an energy storage device arranged to store electrical energy passed by the filter.
7. The acoustic telemetry unit according to claim 6 , wherein the detector comprises a threshold detector arranged to detect when the electrical energy stored on the energy storage device exceeds a threshold.
8. The acoustic telemetry unit according to claim 1 , wherein the detector comprises a switching device arranged to turn on the wake-up circuit when the signal passed by the filter is detected.
9. The acoustic telemetry unit according to claim 1 , wherein the detector is arranged to compare the signal passed by the filter to a signal which is received by the acoustic receiver and not passed by the filter.
10. The acoustic telemetry unit according to claim 1 , further comprising a voltage multiplier arranged to multiply a voltage at an output of the filter.
11. The acoustic telemetry unit according to claim 1 , further comprising:
an energy storage module arranged to supply electrical power to the acoustic telemetry unit; and
a charge circuit arranged to charge the energy storage module using signals received by the acoustic receiver which are not passed by the filter.
12. The acoustic telemetry unit according to claim 11 , wherein the charge circuit comprises a charge storage device arranged to store charge produced by the signals received by the acoustic receiver which are not passed by the filter.
13. The acoustic telemetry unit according to claim 12 , further comprising an alternating current (AC) to direct current (DC) converter arranged to convert an AC signal received by the acoustic receiver to a DC signal for supply to the charge storage device.
14. The acoustic telemetry unit according to claim 1 , wherein the acoustic receiver comprises a transducer arranged to convert acoustic signals to electrical signals.
15. The acoustic telemetry unit according to claim 1 , wherein the acoustic telemetry unit is for use in a wellbore.
16. The acoustic telemetry unit according to claim 1 , wherein the acoustic telemetry unit is an acoustic repeater.
17. A method of operating an acoustic telemetry unit, the method comprising steps of:
receiving acoustic telemetry signals;
filtering, by a filter, the acoustic telemetry signals received in the receiving step;
processing a signal passed by the filter in the filtering step to recover a data signal;
detecting the signal passed by the filter; and
waking the acoustic telemetry unit from a sleep mode when the signal passed by the filter is detected.
18. The method according to claim 17 , further comprising:
supplying power to the acoustic telemetry unit from an energy storage module; and
charging the energy storage module using signals which are not passed by the filter in the filtering step.