SigScope Help

SigScope – Time-domain, frequency-domain, and stochastic signal analysis.

Version 1.00 – 2026. Author: Prof. FAO Nascimento, Electrical Engineering Department, University of Brasilia – UnB.

Open this guide from Help on the menu bar, the toolbar help icon, or F1. Click the SigScope icon on the title bar for a short identity card with the current date and time.

Contents

1. Program details
2. Getting started
3. Main window
4. Menus
5. Main toolbar
6. Opening files
7. Plot menu
8. Time-domain window
9. Time–frequency windows
10. Autocorrelation / autocovariance
11. Signal windowing (DFT tapers)
12. Configure
13. Keyboard shortcuts

Program details

SigScope is a Windows desktop viewer for discrete-time signals. It opens files into a memory buffer, lets you choose channels, and plots them in dedicated windows:

• Time domain — waveforms versus sample index or elapsed time.
• Frequency domain — DFT magnitude, magnitude and phase, or periodogram, always shown together with the time window that produced them.
• Stochastic analysis — autocorrelation or autocovariance of the same time window (DFT method).

The shell is a compact Fusion bar (title, menus, toolbar). Plotting uses PyQtGraph. File I/O is through ScyIO_UnB. The Qt style is Fusion only; chrome and plot colors can be changed, but the style cannot.

New plot windows take their defaults from Parameter configuration (folders, N, advance, speed, gain, layout, axes, DFT settings, grid, pen width, trace colors, plot size, and .sig defaults). Save Configuration writes those values together with system colors into one JSON file. Read Configuration loads that file and applies folders, colors, and plot defaults immediately.

Exit (title-bar close, File → Exit, or the Exit toolbar icon) quits at once. There is no save-configuration prompt and no “Save Configuration and Exit” command.

Getting started

1. Use File → Open or the Open icon to load one or more signal files. Each Open adds files; earlier files stay in memory until you clear the buffer.
2. Use View or the header icon to inspect a file’s parameter summary.
3. Use Plot to pick channels (first checked is 1 at the top), then a plot type. Time domain allows up to 16 signals; the other views allow up to 8.
4. Use the plot-window toolbar to change N, range, sliding, display mode, and to save an image. Close a plot with its Exit icon to return to the SigScope shell.

Main window

The main window is a compact control bar: custom title bar, menu bar, and toolbar. Drag the title bar to move the window. Drag the left or right edge to change width. Height stays locked to the chrome. The status bar is hidden.

Title bar (left to right)

Control	Action
	SigScope icon (sigscope.ico / application icon) — open the identity window: SigScope – Time-domain, frequency-domain, and stochastic signal analysis. Version: 1.00 – 2026 Author: Prof. FAO Nascimento Electrical Engineering Department University of Brasilia – UnB Date and Time from the computer clock at the moment you click.
Title text	SigScope, plus a short note when files are open. Drag here to move the window.
−	Minimize — hide SigScope to the taskbar.
×	Close — quit immediately (same as File → Exit). No save prompt.

Menus

File

View

Lists every file currently in the buffer. Choose a file to open its parameter summary (the header text returned by ScyIO_UnB). If two files share the same name, the folder path is shown so you can tell them apart. When nothing is open, the menu shows “(No files open)”.

The toolbar header icon does the same thing: one open file opens that summary; several files present the same list.

Plot

Each command opens a channel-selection dialog, then a plot window. Plot items are disabled until at least one file is in the buffer. See Plot menu below for the five views.

Configure

See Configure for the folder list and what is stored in the file.

Help

A direct menu-bar command (no submenu). Opens this guide. Same as the toolbar help icon and F1.

About

Main toolbar

Icons, left to right, then the two text buttons, then Exit:

Icon	Control	Action
	Open	Load signal files into the buffer (same as File → Open). Starts in the Signal files folder.
	Signal File Header	Show the parameter summary of an open file. Several files: click to choose which header to view (same as View).
	Clear File Buffer	Remove all open files from memory (same as File → Clear File Buffer).
	Help	Open this guide (same as Help on the menu bar and F1).
	System configuration	Read-only snapshot of the current folders, default plot parameters, and Fusion system colors. Use Parameter configuration or System colors to edit.
	Parameter configuration	Edit folder paths and default plot parameters (same as Configure → Parameter configuration).
	System colors	Choose Fusion chrome and plot color tokens (same as Configure → System colors).
	Read Configuration (text)	Load a JSON configuration file (same as Configure → Read Configuration).
	Save Configuration (text)	Write system colors and parameters to JSON (same as Configure → Save Configuration).
	Exit	Quit SigScope immediately (same as File → Exit).

Opening files

Formats read through ScyIO_UnB:

File → Open and the Open icon start in the Signal files folder (the SigScope application directory until you change it). When a sampling frequency is found (file metadata, or a timestamp column), plots can show elapsed time in seconds. Otherwise the x-axis stays in sample index.

Plot menu

Each Plot command opens a channel-selection dialog, then a PyQtGraph window. Check signals in the order you want them stacked: the first selected is 1 at the top. Time-domain traces can be dragged left/right to shift the sample window (hand cursor).

Time domain

Waveforms versus sample index or time. Up to 16 signals. Several signals default to a stacked layout (one plot per signal); you can overlay them. Height doubles when more than one signal is stacked. N is not restricted to a power of 2. Zoom (magnifying-glass icon) is available only on this window.

Time – frequency magnitude

Time window plus single-sided DFT magnitude |X(f)| (scaled by 1/N). Up to 8 signals. One signal: time on top, magnitude below. Several signals: time | magnitude side by side.

N is a power of 2 (default 1024, min 4, max 65536). The sine–cosine FFT table is built once and rebuilt only when N changes. Time–frequency plots round N from Parameter configuration to the nearest power of 2.

Time – frequency magnitude and phase

Same as magnitude, plus DFT phase in degrees on −180° to +180° (four-quadrant arctangent of Re{X} and Im{X}). One signal: time, magnitude, then phase stacked. Several signals: time | magnitude | phase on each row.

Time – periodogram

Same layout as magnitude, but the spectrum is the squared magnitude of the DFT coefficients: |X[k]|² for k = 0 … N/2.

Time – autocorrelation/autocovariance

Same layout as magnitude (time | correlation). Computation: zero-pad the N samples to 2N, take the DFT, form |X[k]|² for all 2N bins, inverse DFT, plot the first N lags (0 … N−1). Autocovariance is identical except X[0] (DC) is set to zero before the inverse DFT. The frequency-axis icon is not shown on this window; the autocorrelation/autocovariance toggle is shown instead.

Time-domain window

One control bar. Text controls on the left; icons on the right (after a spacer). New windows take N, auto range, gain, sliding speed, advance, grid, layout, waveform mode, time axis, pen width, marker size, trace colors, and window size from Parameter configuration.

Left side (text controls)

• numder of samples — visible window length N (not restricted to a power of 2). Type a new value and press Enter to redraw. The ◀ ▶ buttons next to that field are N/2 and 2N (halve or double the window, then redraw).
• Auto range — automatic vertical scale. Off: set value min / value max, or use Gain +/− (each step is the Gain % of the original Y span; default 20%).
• Sliding — advance the window automatically. Speed is hops per second. Off: static window; use the ◀ ▶ buttons after Advance, or drag the plot.
• Advance — hop size as a percent of N (default 1%). ◀ previous window, ▶ next window.
• Grid — show or hide the plot grid.

Drag a time plot left or right with the left mouse button to shift the sample window (hand cursor).

Right side — icons, left to right

Icon	Control	Action
	Signal name	Show or hide the signal-name legend.
	Layout	Stacked vs overlay (enabled when more than one signal is plotted).
	Waveform	Continuous line vs discrete samples (stems and markers).
	Time / sample	Sample index vs elapsed time in seconds (needs fs on every selected signal).
	Zoom	Arm zoom, then drag a time range. Click again to restore the previous view. Time-domain window only.
	Save plot	Save as SVG, PNG, or JPG. Choose the format with the tumbler immediately to the right of this icon. The save dialog starts in the Plot images folder. The image uses a white background; signal names, when shown, are written in black. A confirmation dialog appears before the file is written.
	Close plot	Close this plot window and return to the SigScope shell. Does not quit SigScope.

Time–frequency windows

These windows (magnitude, magnitude and phase, periodogram, autocorrelation/autocovariance) share one control-bar layout. Differences from time domain are noted below.

Left side (text controls)

• Window length is a power of 2 (default 1024, min 4, max 65536). The ◀ ▶ buttons next to that number are N/2 and 2N (halve or double the FFT length). The sine–cosine FFT table is rebuilt only when N changes.
• The ◀ ▶ buttons after Advance still step the time window, as in the time-domain view.
• Signal windowing (immediately after Grid) — choose the DFT taper. The button shows the type currently in use; default is Rectangular (no taper). The window multiplies the time samples before the FFT; the time trace still shows the raw samples.
• Auto range, Gain, and value min/max apply to the time plots only. Magnitude auto-scales. Phase is fixed at −180° … +180°.

Right side — icons, left to right

Not every icon appears on every time–frequency window. The table lists them in toolbar order.

Icon	Control	Action
	Signal name	Show or hide legends. All time–frequency windows.
	Autocorrelation / autocovariance	Correlation window only, immediately after the name icon. Off: autocorrelation R(τ). On: autocovariance C(τ) (X[0] = 0 before the inverse DFT).
	Time waveform	Continuous vs discrete display of the time trace.
	DFT / spectrum display	Continuous vs discrete display of the DFT magnitude, phase, periodogram, or correlation trace.
	Frequency axis	Cycle: Hz (needs fs) → coefficient index k → normalized frequency k/N in [0, 0.5] → Hz. Not shown on the autocorrelation/autocovariance window.
	Time / sample	Time vs sample index on the time plot. On the correlation window this also switches lag units (samples vs seconds).
	Save plot	Same as on the time-domain window: tumbler for SVG / PNG / JPG, starts in the Plot images folder, white background, black signal names when the legend is shown, confirmation before writing.
	Close plot	Close this plot window and return to the SigScope shell. Does not quit SigScope.

There is no stacked/overlay layout icon and no zoom icon on time–frequency windows.

Autocorrelation / autocovariance

1. Take N samples (power of 2), optionally multiplied by the selected DFT window.
2. Zero-pad to length 2N and compute the DFT (lookup table reused until N changes).
3. Form |X[k]|² for all 2N bins.
4. Autocovariance only: set the DC coefficient X[0] to zero.
5. Inverse DFT → 2N samples; plot the first N lags (0 … N−1).

R(0) of the autocorrelation equals the energy of the (windowed) block.

Signal windowing (DFT tapers)

Available from Signal windowing on time–frequency, periodogram, and correlation windows:

Rectangular (default); Exact Blackman; Blackman; Nuttall; Blackman–Nuttall; 4-term and 7-term Blackman–Harris; Low side-lobe; ISO, E-ISO, and HP P401 flat-top; Heinzel HFT70, HFT95, HFT90D, HFT116D, HFT144D, HFT196D, HFT223D, HFT248D; Perfectly flat-top / equiripple; Ultraspherical (JH); Ultraspherical (Dolph–Chebyshev / Saramäki).

Configure

System colors

Fusion chrome and plot color tokens: window background, chrome / toolbar, title bar, accent, text, button, border, plot background, plot foreground. Restore defaults returns the built-in dark palette. The Qt style stays Fusion.

Parameter configuration

Opens from Configure → Parameter configuration or the parameters toolbar icon. Restore defaults returns built-in values (folders return to the SigScope application directory).

Folders (each has Browse…; default is the folder that contains SigScope.py, or SigScope.exe when frozen):

• Signal files — File → Open and the Open icon start here.
• Configuration files — Read Configuration and Save Configuration start here.
• Plot images (SVG / PNG / JPG) — the camera save dialog on plot windows starts here.

Default parameters used when a new plot window opens: window length N; Advance; Sliding speed; Gain step; Auto range; Layout (stacked / overlay); Time axis; Waveform (continuous / discrete); DFT display; Frequency axis; DFT window; Grid and grid opacity; Pen width; Marker size; Antialias; Plot window size; default .sig fs and sample type; trace colors (16).

System colors are not in this dialog. Time–frequency plots round N to the nearest power of 2.

System configuration (toolbar, view only)

Shows the same folders, default parameters, and the Fusion colors currently in use. It does not edit them.

Read Configuration

Load a JSON file. The file dialog starts in the Configuration files folder. A successful load applies:

• Fusion system colors (the chrome updates at once);
• Parameter configuration, including the three folder paths;
• plot defaults for the next new plot window.

After a load, Open starts in that file’s signal-files folder, Read/Save Configuration start in its configuration-files folder, and plot-image save starts in its plot-images folder. If the system-configuration snapshot is open, it refreshes.

Save Configuration

Write one JSON file with system colors and parameter configuration (folders, N, advance, speed, gain, layout, axes, DFT window, grid, pen width, trace colors, plot size, .sig defaults), plus session paths and the list of open files. Empty folder fields are stored as the SigScope application directory. The file dialog starts in the Configuration files folder.

Keyboard shortcuts

SigScope Version 1.00 – 2026 — Electrical Engineering Department, University of Brasilia – UnB.