Communication protocol in directional drilling system, apparatus and method utilizing multi-bit data symbol transmission

Patent metadata

Field	Value
Publication number	US-9739140-B2
Application number	US-201514845231-A
Country	US
Kind code	B2
Filing date	Sep 3, 2015
Priority date	Sep 5, 2014
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A system includes a transmitter for use in conjunction with a horizontal directional drilling system that transmits a multi-bit symbol stream that characterizes sensor symbols for receipt by an aboveground portable device. The portable device receives the symbol stream for aboveground recovery of the sensor signals. The transmitter can precisely place the symbol frequencies at least to avoid a noise environment, as well as to avoid powerline harmonics, and can utilize wave shaping for transmitted symbols at least to provide for transmission power control, spectral content control and wideband antenna matching. The receiver can measure the noise environment to identify the symbol frequencies used by the transmitter. The noise can be scanned at an incremental resolution across a wide frequency bandwidth for display or automatic symbol frequency selection.

First claim

What is claimed is:

1. A transmitter for use in conjunction with a horizontal directional drilling system that includes a drill string that extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string moves the inground tool through the ground during an inground operation, said transmitter comprising:
an antenna;
one or more sensors for generating one or more sensor signals;
a processor configured for generating a multi-bit symbol stream based on the sensor signals; and

an antenna driver arrangement for electrically driving said antenna to emit a dipole locating signal, as a depth signal, for aboveground reception at least for use in determining a depth of the inground tool and for electrically driving the antenna based on the multi-bit symbol stream to emit an electromagnetic symbol stream for aboveground recovery of the sensor signals.

2. The transmitter of claim 1 wherein said antenna driver arrangement includes a first driver for electrically driving the antenna to emit the depth signal and a second antenna driver for electrically driving the antenna to emit the electromagnetic symbol stream.

3. The transmitter of claim 1 wherein the multi-bit symbol stream includes at least four different symbols such that each symbol represents at least two bits.

4. The transmitter of claim 3 wherein the symbols are each transmitted at a symbol frequency that is unmodulated such that the different symbols are transmitted at different symbol frequencies.

5. The transmitter of claim 4 wherein said processor is configured for transmitting each of the symbol frequencies at a specified power level based on a power allocation such that one of the symbol frequencies is transmitted at a first power level that is different than a second power level for at least one other symbol frequency.

6. The transmitter of claim 1 further comprising:
a direct digital synthesizer configured to generate the multi-bit symbol stream.

7. The transmitter of claim 6 wherein the direct digital synthesizer includes a first channel dedicated to generating a depth signal for additionally driving the antenna to emit a dipole locating signal and a second channel dedicated to generating the multi-bit symbol stream.

8. The transmitter of claim 7 wherein the depth signal is continuously transmitted at a fixed depth signal frequency, independent of the electromagnetic symbol stream.

9. The transmitter of claim 6 wherein the direct digital synthesizer is operable to generate a plurality of symbol frequencies across a wide frequency bandwidth and the direct digital synthesizer is configured to limit the symbol frequencies to a narrow bandwidth that is less than the wide frequency bandwidth and at least approximately matched to said antenna.

10. A transmitter for use in conjunction with a horizontal directional drilling system that includes a drill string that extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string moves the inground tool through the ground during an inground operation, said transmitter comprising:
an antenna;
one or more sensors for generating one or more sensor signals;
a direct digital synthesizer configured for generating a symbol stream, made up of a plurality of fixed-frequency symbols, and the direct digital synthesizer is configured to customize a drive waveform shape for different symbol frequencies; and
an antenna driver for electrically driving the antenna based on the symbol stream to emit an electromagnetic symbol stream for aboveground recovery of the sensor signals.

11. The transmitter of claim 10 wherein the direct digital synthesizer is configured to transmit across a wide frequency bandwidth in response to the sensor signals such that at least a portion of the wide frequency bandwidth is mismatched to the antenna and to customize the waveform shape at least to control transmitter power consumption associated with the different symbol frequencies which transmitter power consumption would otherwise vary across the wide frequency bandwidth as compared to a constant drive voltage and waveform.

12. The transmitter of claim 11 wherein the wide frequency bandwidth is at least approximately 9 KHz to 45 KHz.

13. The transmitter of claim 10 wherein the direct digital synthesizer includes a set of lookup tables defining a corresponding set of waveform shapes that cover the wide frequency bandwidth and the different symbol frequencies are customized based on the waveform shapes of the series of lookup tables.

14. The transmitter of claim 13 wherein the waveform shapes of the set of waveform shapes change responsive to increasing frequency from a sinusoidal shape to a stepped shape at a particular frequency in the wide frequency bandwidth.

15. The transmitter of claim 14 wherein an uppermost group of the waveform shapes above the particular frequency change from pulse-like to a square wave with increasing frequency.

16. The transmitter of claim 10 wherein said direct digital synthesizer includes a shaper to taper a magnitude of each symbol to start and end with a zero magnitude to limit spectral spreading of the symbols.

17. The transmitter of claim 10 wherein the direct digital synthesizer includes a frequency increment for generating the different symbol frequencies within an overall bandwidth of the transmitter such that one of the symbol frequencies is positionable midway between any given adjacent powerline harmonics of a 50 Hz and 60 Hz powerline frequency.

18. The transmitter of claim 17 wherein each symbol frequency includes a spectrum having a fundamental peak that falls between the given adjacent powerline harmonics and the spectrum exhibits a null at every powerline harmonic frequency of a given one of the 50 Hz and 60 Hz powerline frequencies.

19. A portable device for use in conjunction with a transmitter that is configured to move through the ground in a region during an operational procedure while transmitting a transmitter signal that is receivable by the portable device subject to electromagnetic noise that can vary within said region, said portable device comprising:
a receiver configured to (i) measure the electromagnetic noise and identify a set of symbol frequencies in response to the measured electromagnetic noise for subsequent transmission from said transmitter to form a multi-bit symbol stream based on the set of symbol frequencies, each of which multi-bit symbols corresponds to one of the symbol frequencies, at least to characterize sensor information relating to the operation of the transmitter, and (ii) receive the multibit symbol stream from the transmitter during the inground operation to recover the sensor information.

20. The portable device of claim 19 wherein the receiver is configured to automatically select the set of symbol frequencies.

21. The portable device of claim 19 wherein said receiver is configured to identify at least four symbol frequencies in said set.

22. The portable device of claim 19 further comprising:
an communication arrangement for transferring the identified symbol frequencies to said transmitter such that the transmitter thereafter transmits at the identified symbol frequencies.

23. The portable device of claim 19 wherein said receiver is configured to measure the electromagnetic noise by scanning using an incremental fixed frequency step across a frequency bandwi

Assignees

• Merlin Technology Inc

Inventors

• Zeller Rudolf
• Garrabrant Gary
• Bayliss Timothy
• Mercer John E

Classifications

• E21B7/046 Primary

  horizontal drilling (drilling with mechanical conveying means E21B7/003) · CPC title

• E21B47/13

  by electromagnetic energy, e.g. radio frequency · CPC title

• E21B47/024

  of devices in the borehole (determining slope or direction of the borehole E21B47/022) · CPC title

• E21B7/04

  Directional drilling · CPC title

• G01S11/06 Primary

  using intensity measurements · CPC title