Systems and methods for data transfer using self-synchronizing quadrature amplitude modulation (QAM)

Patent metadata

Field	Value
Publication number	US-9634878-B1
Application number	US-201213609196-A
Country	US
Kind code	B1
Filing date	Sep 10, 2012
Priority date	Sep 8, 2011
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

Quadrature Amplitude Modulation (QAM) methods, apparatus, and systems including a QAM transmit modulator to generate an output signal using a two-dimensional (2-D) QAM symbol constellation is disclosed.

First claim

We claim:

1. A method for providing a self-synchronizing Quadrature Amplitude Modulation (QAM) signal in a video inspection system, comprising:
generating, in a video camera module of a camera head coupled to a push-cable including two or more conductors, a digital video signal comprising a digital data stream representing the interior of a pipe or conduit in which the camera head is deployed into;
receiving, at a QAM transmitter module disposed in the video camera module, the digital data stream;
mapping the digital data stream to ones of a plurality of symbol values corresponding solely to points on a circular symbol constellation, including orthogonal I and Q axes, to generate a mapped data stream; wherein the points defining the circular symbol array are spaced on the circumference of a first circle of the circular symbol array constellation so that the angular distance between a first pair of points in the circular array is different than the angular distance between a second pair of points of the circular array and such that the mapped data stream has substantially zero energy at a symbol clock frequency; and
sending the mapped data stream to the wired communication conductors of the push-cable.

2. The method of claim 1 , wherein the circular symbol constellation is a four or more point array defined on a circle, and two or more symbol pairs are non-uniformly spaced on the circle in a mirror symmetry configuration about the I and/or Q axes.

3. The method of claim 1 , wherein the circular symbol constellation comprises two or more circles with four or more symbols disposed on each of the circles, wherein two or more symbol pairs are non-uniformly spaced on one or more of the two or more circles in a mirror symmetry configuration about the I and/or Q axes.

4. The method of claim 1 , wherein the circular symbol constellation includes a first circle and a second circle, and wherein the digital data stream is mapped to points on the first circle and the second circle.

5. The method of claim 1 , wherein a portion of the digital data is further mapped to ones of a plurality of symbol values corresponding to points on a rectangular symbol constellation.

6. The method of claim 1 , further comprising:
receiving the transmitted signal at a QAM receiver module operatively coupled to the push-cable conductors;
applying the transmitted signal to a non-linearity module to recover the symbol clock by generating a squared version of the transmitted signal; and
decoding the received transmitted signal using the recovered symbol clock.

7. The method of claim 6 , wherein the non-linear module is a square-law processing module configured to square the received transmitted signal.

8. The method of claim 6 , wherein the recovering the symbol clock includes:
narrowband filtering an output of the non-linearity device; and
applying the output of the narrowband filter to a phase-locked loop to generate the symbol clock.

9. The method of claim 1 , wherein the digital data stream is a video data stream generated from a pipe inspection imaging element.

10. The method of claim 9 , further including compressing the video data stream in a camera head before providing the video data stream to the QAM module.

11. The method of claim 1 , wherein at least one symbol point in the circular constellation is on the in-phase (I) axis of the constellation.

12. A method for providing a self-synchronizing Quadrature Amplitude Modulation (QAM) signal from a QAM transmitter module, comprising:
receiving a digital data stream corresponding to a video signal from a camera head disposed in a pipe or cavity;
mapping the digital data stream to ones of a plurality of symbol values corresponding to points on a circular symbol constellation including orthogonal I and Q axes, to generate a mapped data stream; wherein the points defining the circular symbol array are spaced on the circumference of a first circle of the circular symbol array constellation so that the angular distance between a first pair of points in the circular array is different than the angular distance between a second pair of points of the circular array;
wherein the points defining the circular symbol array are spaced such that the mapped data stream includes signal energy at a symbol clock frequency; and
sending the mapped data stream in a wired push-cable communication channel.

13. A QAM transmitter, comprising:
a memory; and
a processor coupled to the memory, the processor configured to:
receive a digital data stream corresponding to a video stream;
map the digital data stream to ones of a plurality of symbol values corresponding solely to points on a circular symbol constellation, including orthogonal I and Q axes, to generate a mapped data stream; wherein the points defining the circular symbol array are spaced on the circumference of a first circle of the circular symbol array constellation so that the angular distance between a first pair of points in the circular array is different than the angular distance between a second pair of points of the circular array and such that the mapped data stream has substantially zero energy at a symbol clock frequency; and
send the mapped data stream as an output signal to a wired push-cable communication channel.

14. The QAM transmitter of claim 13 , further comprising:
a camera head for enclosing the memory and processor; and
a video compression module in the camera head for compressing the digital data stream before the digital data stream is mapped to the ones of a plurality of symbol values.

15. The method of claim 12 , wherein at least one symbol point in the circular constellation is on the in-phase (I) axis of the constellation.

16. The method of claim 12 , wherein the circular symbol constellation is a four or more point array defined on a circle, and two or more symbol pairs are non-uniformly spaced on the circle.

17. The method of claim 12 , wherein the circular symbol constellation comprises two or more circles with a plurality of symbols disposed thereon, wherein two or more symbol pairs are non-uniformly spaced on one or more of the two or more circles.

18. The method of claim 12 , wherein the circular symbol constellation includes a first circle and a second circle, and wherein the digital data stream is mapped to points on the first circle and the second circle.

19. The method of claim 12 , wherein a portion of the digital data is further mapped to ones of a plurality of symbol values corresponding to points on a rectangular symbol constellation.

20. The method of claim 12 , further comprising:
receiving the transmitted signal;
recovering a symbol clock signal from the received transmitted signal; and
decoding the received transmitted signal using the recovered symbol clock.

21. The method of claim 20 , wherein the recovering the symbol clock includes:
narrowband filtering the received transmitted signal; and
applying the output of the narrowband filter to a phase-locked loop to generate the symbol clock.

22. A QAM Transmitter, comprising:
a camera head housing;
a memory disposed in the camera head housing; and
a processor coupled to the memory and disposed in the camera head housing, the processor programmed to:
receive a digital data stream from an imaging sensor in the camera head when the camera head is disposed in a pipe or cavity;
map the digital data stream to ones of a plurality of symbol values corresponding solely to points on a circular symbol con

Assignees

• Bench Stephanie M
• Shaffer Roger B
• Olsson Mark S
• See Scan Inc

Inventors

• Bench Stephanie M
• Shaffer Roger B
• Olsson Mark S

Classifications

• H04L27/3455 Primary

  in order to facilitate carrier recovery at the receiver end, e.g. by transmitting a pilot or by using additional signal points to allow the detection of rotations · CPC title

• H04L27/3405

  Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power · CPC title

• F17D5/00

  Protection or supervision of installations (arrangements for protecting foundations E02D31/00; protecting pipes from damage or internal or external wear F16L57/00, against corrosion and scale F16L58/00; investigation of the fluid-tightness of structures G01M3/00) · CPC title

• H04L27/34 Primary

  Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems · CPC title