Density trace measurement

摘要

A "density trace" according to an embodiment of the present invention is formed by measuring the density of each column of a frequency domain bitmap above a user-specified "amplitude threshold." The density of each column equals the sum of the densities of all of the pixels in the column that are above the amplitude threshold divided by the sum of the densities of all of the pixels in the column. A density trace provides a convenient way to define and represent the occupancy for a large number of columns, and also allows density data to be quickly transmitted from one instrument or computer to another. In some embodiments, a density trace is incorporated into a trigger detector of a test and measurement instrument and used to generate a trigger signal. The trigger detector compares the density trace to a user-specified "density threshold" and generates the trigger signal when the value of any point of the density trace violates the density threshold.