Frequency domain bitmaps triggering using color, density and correlation based triggering

An RF test and measurement device (20), including a front end (22) for receiving a time-varying signal (24) and a real-time engine (30) for generating digital frequency domain spectrums (31) based on the time-varying signal. The device also includes a memory subsystem (32) containing a frequency domain bitmap which is updated through sequential receipt and storage of the digital frequency domain spectrums. The real time engine is further configured to monitor the frequency domain bitmap for occurrence of a signal characteristic, and in response to detection of the signal characteristic, cause a capture of the time-varying signal into a storage location (38) of the RF test and measurement device.