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

Patent metadata

Field	Value
Publication number	US-10069667-B1
Application number	US-201715483924-A
Country	US
Kind code	B1
Filing date	Apr 10, 2017
Priority date	Sep 8, 2011
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

Quadrature Amplitude Modulation (QAM) methods, apparatus, and systems are disclosed.

First claim

We claim:

1. A QAM transmitter for use in a video inspection system, comprising:
a memory;
a processor coupled to the memory, the processor programmed to:
receive a digital data stream comprising images or video; and
map 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 constellation are non-uniformly spaced such that the mapped data stream has substantially zero energy at a symbol clock frequency; and
an output circuit to provide the mapped data stream to a communications channel.

2. The QAM transmitter 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 QAM transmitter of claim 1 , 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 in a mirror symmetry configuration about the I and/or Q axes.

4. The QAM transmitter 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 QAM transmitter 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 QAM transmitter of claim 1 , wherein the digital data stream is a video data stream generated from a pipe inspection camera head.

7. A QAM receiver for use in a video inspection system, comprising:
a receiver front end circuit;
a memory; and
a processor coupled to the memory, the processor programmed to:
receive a digital data stream comprising a plurality of symbol values corresponding to points on a circular symbol constellation including orthogonal I and Q axes representing images or video; and
decode the symbol values to extract the images or video; wherein the points defining the circular symbol constellation are non-uniformly spaced such that a mapped data stream has substantially zero energy at a symbol clock frequency.

8. The QAM receiver of claim 7 , 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.

9. The QAM receiver of claim 7 , 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 in a mirror symmetry configuration about the I and/or Q axes.

10. The QAM receiver of claim 7 , 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.

11. The QAM receiver of claim 7 , 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.

12. The QAM receiver of claim 7 , wherein the processor is programmed to decode the symbol values by:
applying the received digital data to a non-linearity module to recover the symbol clock; and
decoding the received digital data using the recovered symbol clock.

13. The QAM receiver of claim 12 , wherein the non-linear module is a square-law processing module that squarer the received digital data to recover the symbol clock.

14. The QAM receiver of claim 12 , wherein the processor is programmed to recover the symbol clock by:
narrowband filtering an output of the non-linearity module; and
applying the output of the narrowband filtering to a phase-locked loop to generate the symbol clock.

15. The QAM receiver of claim 7 , wherein the digital data stream is a video data stream generated from a pipe inspection camera head.

Assignees

• Seescan Inc

Inventors

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

Classifications

• H04L27/34 Primary

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

• 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