WA Arbitrary Path Decomposition VI
- Updated2024-07-30
- 3 minute(s) read
Performs subband decomposition by cascading the lowpass analysis filters and the highpass analysis filters and applies a decimation factor of 2 after each filtering step. path specifies the subband and determines how to cascade the lowpass analysis filters and the highpass analysis filters. Wire data to the signal input to determine the polymorphic instance to use or manually select the instance.
WA Arbitrary Path Decomposition Details
The following illustration shows an example of an arbitrary path decomposition with the path input set to 101 and the extension input set to Periodic. The length of the input signal is 16 points.
G1(z) denotes that the signal passes through a highpass filter. G0(z) denotes that the signal passes through a lowpass filter. G1(z) and G0(z) form the analysis filter bank. 
denotes a decimation on the signal with a factor of 2. Path 101 indicates that this VI passes the signal through a highpass filter G1(z), through a lowpass filter G0(z), and then through a highpass filter G1(z).
Using information in the previous illustration, you can see that the residual info output contains the information about the complementary subbands at each level, and you can see that the path coef output of this VI contains the coefficients of the subband that path defines.
A discrete wavelet decomposition decomposes the lowpass filtering output, or the approximation coefficients, at each level. However, an arbitrary path decomposition does not restrict the decomposition to the lowpass filtering output. You can use the lowpass filtering output or the highpass filtering output for the further decomposition.
The residual info output stores the information of path 0, path 11, and path 100 in the above example for reconstruction. You can use the source coefficients input of the WA Arbitrary Path Reconstruction VI to select path coefficients and/or residual coefficients to reconstruct the signal.
Examples
Refer to the Engine Knocking Detection VI in the labview\examples\Wavelet Analysis\WAApplications directory for an example of using the WA Arbitrary Path Decomposition VI.