I am implementing the next item on my list and it is almost done: the trigger function.
A modern spectrum analyser has to feature a trigger function, which serves the purpose of alerting the operator whenever a given frequency exceeds a pre-defined treshold value.
Newer spectrum analysers, like the Siglent SSA3021X will actually allow the user to draw lines, which act as treshold values across the setup frequency range.
Naturally, I had to do something even better! The problem with defining a set of line segments to draw the power treshold for an alarm is that it takes ages to define a complex treshold mask.
Also, most spectrum analysers will only alarm if the signal power is greater than the defined treshold, not offering any alarm in case the signal power is lower than a second treshold.
I implemented something slightly different:
- The user saves a bitmap of the current spectrum (using the "SAVE PICTURE" button).
- The user opens said bitmap with Paint (or any other bitmap drawing tool) and draws the upper limit as a blue area and the lower limit as a red area.
- This new bitmap acts as a trigger map.
- Once loaded, the software will extract the exact upper/lower treshold contour and starts monitoring the live spectrum.
- Should any frequency have a higher or lower signal power than specified with the current trigger map, an alarm is issued.
- In the present state, the alarm is shown as a red or blue status message and the individual alarm is put with time stamp and description on a list box.