Computational Signal Processing with Wavelets
A. Teolis, Naval Research Laboratory, Washington D.C.
0-8176-3909-8 * 1997-Spring * $59.95. * Hardcover * 332 pages
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WSPW Main Interface

On startup the WSPW Signal Synthesizer window shown below is spawned.

This window consists of three main user interface panels which hold graphical controls which direct processing actions. The three panels are (from top to bottom )

Each of these panels is discussed below.

Data Type Panel

The Data Type panel is used to specify the type of signal to be synthesized and is one of

Selection of the data type determines the contents of the other panels.

Load Panel

The Load panel is used to select and load a signal from a predefined menu of signals. The user may also specify a level at which to add noise to the clean signal. Depressing the Make button causes the specified signal at the specified noise level to be synthesized, loaded, and displayed in the body of the Loader window. The noise is additive analytic Gaussian noise with the selected signal to noise ratio (SNR) as measured in dB.

All of the one-dimensional (1D) signals in the File(s) menu are analytic (i.e., their Fourier transforms vanish on negative frequencies) and therefore are complex signals. Once a 1D signal is loaded its real part and magnitude are overlayed in a plot in the Loader window. Subsequent processing may now be performed on the loaded signal.

Transform Panel

Transform menu

The Transform panel is used to specify a transformation to apply to a loaded signal. Transforms include

Upon the very first selection of a wavelet transform the wavelet interface is spawned.

alpha parameter

The alpha parameter is generic transform parameter. For the fft it is unused, and for the cwt, fwt, and fwt2, its value is interpreted as a frequency upshift and scale limit respectively. For the cwt the signal to be transformed is first upshifted by the quantity alpha along the frequency axis before the wavelet transform is computed. For the fwt or fwt2 alpha is used to specify the number of scales to compute. The table below summarizes this.

Transform alpha parameter example values
fft unused -

fwt, fwt2

number of decomposition levels

2,3,4,...10,...

cwt

upshift (translation along frequency axis)

 0,10,20, any real


xform button

Depressing the Xform button causes the specified transform to be computed on the loaded signal and displayed in a new window. For example, selecting the fft transform and depressing the Xform button for the case of the opacket signal yields the new window shown below.



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