An eye diagram analyzer assigns a plurality of SUT data signals (8) to be members of a labeled group (5) of channels. There may be a plurality (6,7) of such groups. In addition to mere superposition in an (X, Y) display space of the various i-many (X, Y)-valued pixels for individual component eye diagrams associated with that group, other measured data for those pixels within a group can be merged in various different modes (13) to produce corresponding composite eye diagram presentations (11). E.g., in a Normalized Signal Density Mode the number of hits at each trial measurement point is summed over all channels in the group, and then divided by the total number of clock cycles measured for the i<sub>th</sub> measurement point in that group to produce a density D<sub>i</sub> associated with the corresponding i<sub>th</sub> pixel: (X<sub>i</sub>, Y<sub>i</sub>, D<sub>i</sub>). If D<sub>i</sub> is rendered as a color or an intensity, the resulting eye diagram includes a representation (the D<sub>i</sub>) of a normalized density of transitions at each point (X<sub>i</sub>, Y<sub>i</sub>), relative to that group as a whole. As a further example, in a Channel Density Mode, each D<sub>i</sub> is produced by accumulating, for each of N-many channels, a 1/N for each sample (value of i) with non-zero signal activity, and dividing the accumulation by N. If that collection of D<sub>i</sub> is rendered as a color or an intensity, the resulting composite eye diagram includes a representation (the D<sub>i</sub>) at each (X<sub>i</sub>, Y<sub>i</sub>) point of the degree of coincidence among, or a degree of similarity between, the channels in the group.
Method of creating a composite eye diagram