Patent ID: 9634878
Date: 2017-04-25
CPC Classifications: F17D,H04L

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.