In many signal analysis tasks, it is useful to focus only on the "good" parts of a signal - those segments that are clean, relevant, or contain key events - while ignoring unwanted sections.

Manually extracting these parts, performing spectral analysis on each, and combining the results can be time-consuming and tedious.


To simplify this process, SIGVIEW offers a Segment Selection and FFT Analysis feature, allowing you to easily select desired signal parts and perform FFT on them.


Selecting Segments from a Signal


You can control segment selection through the signal’s context menu (right-click on the signal), under the Segments section.



Available options include:


Start Segment Here: Marks the beginning of a new segment at the current cursor position.


End Segment Here: Marks the end of the current segment at the cursor position.


Create Segment from Selection:

Creates a new segment based on the current mouse selection range.


oDelete This Segment: Deletes the segment currently under the signal cursor.

oClear All Segments: Removes all defined segments from the current signal.

oFFT on Selected Segments: Performs FFT analysis on the selected segments (detailed below).



Visual Representation


Selected segments are highlighted with a green background behind the signal.


The start of an unfinished segment is indicated by a thin green vertical line.



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Saving and Reloading Segments


When you save a Workspace using File / Save Workspace... or Save as Tool..., all segment information is preserved along with the signal. Reloading the workspace will restore your segment selections.



Notes on Segment Behavior


If a new segment overlaps an existing one, SIGVIEW will automatically merge them into a single, larger segment.


You cannot manually edit segment boundaries. To adjust a segment, you must delete it and define a new one.



Performing FFT on Selected Segments


SIGVIEW performs FFT analysis on the selected segments by:


•Dividing each segment into smaller, overlapping blocks.

•Calculating FFT for each block.

•Averaging the FFT results across all blocks and segments to create a final spectrum.


Setting FFT Parameters


After selecting your segments and choosing "FFT on Selected Segments", a dialog will appear where you can configure FFT parameters:



Single FFT Length: Defines the length of the FFT for each block. Options are limited by the size of the smallest segment (up to 512K samples).


FFT Overlap: Choose the amount of overlap between FFT blocks (25%, 50%, 75%, None)


Note: If perfect overlap settings do not fit into the selected segment length, SIGVIEW may slightly adjust the overlap percentage (e.g., from 50% to 48%) to match the available data.



Behavior of the Resulting FFT Window


The FFT result window created from segment analysis behaves like any other FFT window in SIGVIEW:


•You can edit its properties (e.g., window function, scaling, averaging).

•You can save it using “Save Workspace...” or “Save as Tool...”.

•Each time you modify the selected segments, SIGVIEW automatically recalculates the FFT and updates the display.

•You can create multiple FFT windows from the same segments but with different FFT settings to compare the effect of different parameters on the result.