Patent ID: 8345736

Claim:
A sampling point detection circuit for detecting a sampling point in an eye diagram, comprising: division line setting means for successively setting amplitude division lines along a time axis and time division lines along an amplitude axis in a translational manner in said time and amplitude axis directions, respectively, on a virtual plane having coordinate axes that are said time and amplitude axes of an eye diagram; virtual circle calculation means for calculating a virtual circle that is inscribed in a divided region having the smallest area among four divided regions obtained when a region that is defined by segments each connecting intersections of a bit error rate contour line of an input eye diagram and said amplitude division line set by said division line setting means and intersections of said bit error rate contour line and said time division line set by said division line setting means and that contains an intersection of said amplitude division line and said time division line is divided by such amplitude division line and time division line; and sampling point determination means for determining, as a sampling point in the eye diagram in question, the intersection of said time division line and said amplitude division line that are set when the largest virtual circle is calculated among said virtual circles calculated by said virtual circle calculation means.