Frequency mask trigger with non uniform bandwidth segments

Disclosed is a test and measurement instrument (200) having a multiple variable bandwidth frequency mask. The instrument includes an input processor (205, 210, 220) for receiving an input signal and producing a digital signal, as well as a trigger signal generator (260, 262) for generating a trigger signal on the occurrence of a trigger event. A time to frequency converter (250, 252) converts a frame of digital data from the digital signal into a frequency spectrum having at least two frequency bins of dissimilar frequency widths. Each frequency bin has a power amplitude value. The trigger signal is generated when the power amplitude value of any of the at least two frequency bins violates an associated reference power level. In some cases the output may be shown as a density trace, and the trigger signal generated when any point of the density trace violates an associated density threshold.