SigScope

Version 1.00 – 2026

SigScope – Time-domain, frequency-domain, and stochastic signal analysis. Author: Prof. FAO Nascimento, Electrical Engineering Department, University of Brasilia – UnB.

SigScope is a Windows desktop viewer for discrete-time signals. It uses a compact Fusion shell (title bar, menus, toolbar), PyQtGraph for plots, and ScyIO_UnB for file I/O. Open Help for menus, every toolbar icon, and plot-window controls.

1. File formats that can be read and processed

Open (File → Open, the folder icon, or Ctrl+O) loads files into a buffer. Each Open adds files; previous ones stay in memory until Clear File Buffer.

Sampling frequency fs is taken from file metadata (fs / Fs / dt, HDF5 attributes, CSV/Parquet scalars) or derived from a timestamp / timestamps column as 1/(t₁−t₀). Timestamp itself is not plotted. If fs is known for every selected channel, plots can show elapsed time in seconds; otherwise the x-axis stays in sample index.

View lists every open file so you can inspect its parameter header.

2. Graphical windows: visualization, analyses, and tools

From Plot, you pick channels in the order you want them stacked (first selected at the top), then a view. Time domain allows up to 16 signals; the other views allow up to 8.

Plot types

• Time domain — waveforms vs sample index or time. Several signals default to stacked plots (one per signal); height doubles when stacked. They can be overlaid on one plot.
• Time – frequency magnitude — time window plus single-sided DFT magnitude |X(f)|/N. One signal: time above, spectrum below. Several signals: time | magnitude side by side.
• Time – frequency magnitude and phase — same, plus phase in degrees on −180° to +180° (four-quadrant arctangent of Re and Im).
• Time – periodogram — same layout as magnitude, with unnormalized |X[k]|² for k = 0 … N/2.
• Time – autocorrelation/autocovariance — same layout as magnitude. Length-2N DFT of the N-sample block, |X|², inverse DFT, first N lags. Autocovariance zeros DC (X[0]) before the IDFT.

The FFT is a radix-2 transform with a sine–cosine lookup table, rebuilt only when N changes. N is a power of 2 (default 1024, min 4, max 65536).

Shared plot tools

• Window length N, Auto range, Gain +/−, value min/max
• Sliding window with Speed (hops/s) and Advance (% of N)
• Step the window with ◀ ▶, or drag the plot (hand cursor)
• Grid
• Time vs sample index; continuous line vs discrete stems
• Signal-name legend
• Exit icon returns to the SigScope shell

Time-domain extras: stacked vs overlay; zoom (drag a time range, click again to restore).

Time–frequency extras: N/2 and 2N next to window length; Signal windowing (Rectangular default, then Blackman, Nuttall, Blackman–Harris, flat-top / HFT, ultraspherical, and others). The taper is applied only before the FFT. DFT display can be continuous or discrete. Frequency axis cycles Hz → coefficient index k → normalized [0, 0.5]. Autocorrelation/autocovariance adds the R(τ)/C(τ) toggle and omits the frequency-axis icon.

Configure covers Fusion system colors, Parameter configuration (folders for signals, configuration files, and plot images, plus defaults for new plot windows), and Read/Save Configuration (JSON: folders, colors, pen width, plot defaults). Folder paths default to the SigScope application directory. The toolbar system configuration icon shows the current folders, defaults, and colors.

3. User help system

Help is a scrollable HTML guide (icons included), not a short message box.

Open it from:

• Help on the menu bar (opens the guide directly; no extra submenu)
• The help icon on the toolbar
• F1

The guide covers getting started, menus and toolbar icons, file formats, every plot mode, plot-window controls and icons, DFT windowing, autocorrelation vs autocovariance, configuration, and shortcuts.

About has three items: SigScope (this summary), The author, and Acknowledgments. Clicking the SigScope icon on the title bar shows a short identity card (version, author, and the current date and time).

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