Multiresolution Analysis Express VI

LabVIEW 2014 Advanced Signal Processing Toolkit Help

Edition Date: June 2014

Part Number: 372656C-01

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Owning Palette: Discrete Wavelet VIs

Requires: Advanced Signal Processing Toolkit

Decomposes a signal according to the level you specify and reconstructs the signal from the frequency bands you select.

Example

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
Data SourceSpecifies whether this Express VI reads data from a block diagram input terminal or from a file. From terminal specifies that this Express VI reads data from a block diagram input terminal. From file specifies that this Express VI reads data from a file. This Express VI can read data from waveform, WAV, or TXT files. The valid format of a TXT data file is a file that contains only a 1D real array.
File Path ConfigurationContains the following options:
  • File path—Specifies and displays the path to the file from which this Express VI reads data. This option is available only when you select From file in the Data Source section.
  • Prompt to choose a file each time this VI runs—Specifies whether this Express VI displays a dialog box that prompts you to select a file each time this Express VI runs. This option is available only when you select the From file option in the Data Source section.
Original and Reconstructed SignalDisplays the original and reconstructed signal.
Wavelet Transform and Subband SelectionContains the following options:
  • Frequency bands—Specifies the subbands or the parts of subbands to use to reconstruct the signal. The discrete wavelet transform (DWT) decomposes a signal into a series of dyadic frequency subbands.
  • Zoom out—Zooms out the frequency bands near DC, which is the origin of the x-scale of Frequency bands.
  • Zoom in—Zooms in the frequency bands near DC, which is the origin of the x-scale of Frequency bands.
  • Select all—Selects all the frequency bands. Click this button to reconstruct the image from the approximation coefficients and the detail coefficients of all the frequency bands.
  • Levels—Specifies the number of levels in the discrete wavelet analysis. Levels must be a positive integer no greater than log2(Ls), where Ls is the length of the signal.
  • Wavelet—Specifies the wavelet type this Express VI uses for discrete wavelet analysis. The default is db02. You can choose from the following options:
    • Customized Wavelet
    • Haar—Orthogonal
    • dbxx—Orthogonal, Daubechies
    • coifx—Orthogonal, Coiflets
    • symx—Orthogonal, Symmlets
    • biorx_x—Biorthogonal
    • bior4_4 (FBI)—Biorthogonal, FBI
    where x indicates the order of the wavelet. The higher the order, the smoother the wavelet.
    Note  The orthogonal wavelets are not redundant and therefore are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and therefore are suitable for signal or image feature extraction.
FunctionsDisplays the following graphs:
  • Analysis scaling—Displays the scaling function of the analysis filter bank.
  • Analysis wavelet—Displays the mother wavelet of the analysis filter bank.
  • Synthesis scaling—Displays the scaling function of the synthesis filter bank.
  • Synthesis wavelet—Displays the mother wavelet of the synthesis filter bank.
FiltersDisplays the following graphs:
  • Analysis lowpass (G0)—Displays the coefficients of the lowpass analysis filter G0(z).
  • Analysis highpass (G1)—Displays the coefficients of the highpass analysis filter G1(z).
  • Synthesis lowpass (H0)—Displays the coefficients of the lowpass synthesis filter H0(z).
  • Synthesis highpass (H1)—Displays the coefficients of the highpass synthesis filter H1(z).
Parameters SettingsContains the following options:
Note  The following options are available only if you select the Customized Wavelet option from the Wavelet pull-down menu.
  • Wavelet Type—Specifies the type of wavelet this Express VI uses to design a customized wavelet for discrete wavelet analysis and reconstruction. You can select the Orthogonal or Biorthogonal option.
  • Product of Lowpass (P0=G0*H0)—Specifies P0, which is the product of the lowpass analysis filter G0 and the lowpass synthesis filter H0. Contains the following options:
    • P0 type—Specifies the type of P0. The default is Maxflat. You can choose from the following options:
      • Maxflat
      • Positive Equiripple
      • General Equiripple
      Note  The General Equiripple option is available only if you select the Biorthogonal option in the Wavelet Type section.
    • Zero pairs at pi (P0)—Specifies the value of p in the Maxflat filter P0(z), where P0(z) = (1+1/z)^(2p)*Q(z). This option is available only if you select the Maxflat option in the P0 type section.
    • # of taps—Specifies the number of coefficients of P0(z). The length of P0(z) must be 4p–1, where p = 2, 3, …. This option is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section.
    • Passband—Specifies the normalized cutoff frequency of P0(z). The value of Passband must be less than 0.5. Passband is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section.
  • Factorization (Type of G0)—Contains the following options:
    • Filter type—Specifies how this Express VI factors P0 to G0 and H0. Contains the following options:
      • Arbitrary—Specifies that no restriction exists on the placement of zeros.
      • Minimum Phase—Specifies that the zeros of G0 are located inside the unit circle, except for the zeros at pi.
      • Linear Phase—Specifies that if one zero belongs to G0(H0), the reciprocal of that zero must belong to G0(H0).
      • B-Spline—Specifies that except for some zeros at pi, all the zeros of P0 belong to H0.
    • Zeros at pi (G0)—Controls how many zeros at z=–1 belong to G0(z). This option is available only if you select the Maxflat option in the P0 type section. The maximum value of this option is 2p, where p = the value of the Zero pairs at pi (P0) option.
Zeros of G0 and H0Shows the distribution of the zeros of P0(z), G0(z) and H0(z). This Express VI uses this distribution to factor the zeros of P0(z) into the zeros of G0(z) and H0(z). Because the filter coefficients of P0(z) are real, all the zeros of P0(z) are symmetrical with respect to the x-axis. Consequently, this Express VI displays only the upper half of the plane. The zeros on the x-axis represent real-valued roots. The zeros outside of the x-axis represent complex-valued roots.

The blue crosses represent the zeros of G0(z), and the red circles represent the zeros of H0(z).

Click on the zero you want to select to switch the zero from that of G0(z) to that of H0(z) and vice versa. All the zeros belong to G0(z) or H0(z).

Selecting different values for Filter type puts different constraints on the selections of zeros. For example, if you select Linear Phase for Filter type and select a zero for one filter, the filter automatically contains the reciprocal of the zero.
Note  This section is available only if you select the Customized Wavelet option from the Wavelet pull-down menu.

Block Diagram Inputs

ParameterDescription
error in (no error)Describes error conditions that occur before this node runs.
SignalSpecifies the block diagram terminal of the data you want to load. This input is available only if you select the From terminal option in the Data Source section.
File pathSpecifies the file path of the data you want to load. This input is available only when you select the From file option in the Data Source section.

Block Diagram Outputs

ParameterDescription
ReconstructionReturns the reconstructed signal.
error outContains error information. This output provides standard error out functionality.

This Express VI operates similarly to the following VIs and functions:

WA Discrete Wavelet Transform
WA Inverse Discrete Wavelet Transform

Example

Refer to the Multiresolution Analysis - 1D Signal VI in the labview\examples\Wavelet Analysis\WAGettingStarted directory for an example of using the Multiresolution Analysis Express VI.

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