Unlike most other signal analysis applications, SIGVIEW does not merely provide a fixed user interface for all purposes. It is rather designed as a collection of tools which can be combined in many different ways to create a user interface and functionality customized to your analysis. Once you have created your toolchain, you can save your application-specific “workspace” or "tool" and reuse it later. To be able to use the full power of SIGVIEW, it is very important to understand a several basic concepts:
Analysis chain: All signals or signal analysis results in SIGVIEW are connected to other windows to form a chain of functional blocks: file input, data acquisition, FFT, instruments…You can imagine signals or analysis results to “flow” through that chain from one tool to another one, following your analysis path. Each time the content of one window changes, all its child windows will recalculate and redraw its content. The analysis chain could look like this (Control Window display):
Visible part of the signal: If you perform any analysis on a signal window, it will be performed only on the currently visible part of the signal. Consequently, if you change the visible part of the signal (by moving through the signal, zooming in or out,…), all child windows will recalculate and redraw its content accordingly. This feature, together with different playback/navigation functions, provides a very powerful method to control control the analysis and simulate real-time analysis with offline signals.
Every array of values is a “signal”: Each sequence of X/Y values is considered to be a "signal" (audio signal, spectrum, etc.). Consequently, each sequence has its sampling rate, even if it was not actually created by digitally sampling some analog signal. Sampling rate of an FFT is simply a number of its values (bins) in one X-axis unit, Hz. Following this logic, it is possible to perform, for example, FFT analysis on an FFT result. Even if it seems as if it does not make sense, it can sometimes be interesting to see the results. The important thing is that SIGVIEW does not impose any artificial limitations, telling you what you should and what you should not do. You are free to experiment and to find you own method of getting the results you want.
Signal graph/Linked windows: If one window is created as a result of the analysis from any other window, then those two windows are linked. The network of linked windows works like a complex analysis machine where the output of each window is the input for its child windows. It means that all changes in one window will cause its child windows to recalculate and redraw their content. A good example is a part of the signal and it’s FFT; if you slide a part of the signal through the whole signal, its FFT result window will recalculate on each move to show the FFT result of each new signal segment.
Moving through signals: You will usually work and perform analysis on a small part of a longer signal. If your signal is zoomed-in to a smaller part, you can use arrow keys or playback commands to move through the signal and observe changes in analysis results. One of the standard procedures for working with signals would be:
- Load one long signal and zoom-in to some power-of-2 length segment
- Perform some analysis on that segment, for example FFT
- Use "Track changes as 3D graphics" function on that calculated FFT
- Return to the signal window and use left/right arrow keys to move the segment through the whole signal
- That way, you will be able to observe spectral changes in a signal through time and "record" consecutive spectra in a 3D graphics
Data acquisition/monitoring: You can work with a data acquisition window as you would with any other static signal window. The only difference is that the signal you are recording will change (if data acquisition is started) at regular intervals, depending on your data acquisition settings. That will cause your signal analysis system to recalculate and redraw all windows connected with the data acquisition window. If your PC is fast enough, you will be able to create or change your analysis system while data acquisition is running; otherwise it might be better to create the system first and then begin the data acquisition and observe the results.
Control window: Working with many signals and analysis windows at the same time can become quite confusing. In those situations, you can use the Control Window to display your signal analysis system in a tree-view form where you can easily understand signal flow, perform operations on multiple signals, hide and show windows and choose which signals to show as overlay.
Properties: You can change parameters for most analysis windows, even after they are created. If this is possible, Edit/Properties menu options will be enabled in the main menu or in the context menu for that specific window. By using this option, you will be able to change window properties like cut-off frequencies for filtered signal, spectral analysis settings for FFT and Time-FFT, scale limits for instruments, etc.