Signal Processing Toolbox

Importing Filters and Spectra into SPTool

In addition to importing signals into SPTool, you can import filters or spectra into SPTool from either the workspace or from a file.

The procedures are very similar to those explained in:

• Step 1: Importing a Signal into SPTool for loading variables from the workspace
• Loading Variables from the Disk for loading variables from your disk

Importing Filters

When you import filters, first select the appropriate filter form from the Form list.

For every filter you specify a variable name or a value for the filter's sampling frequency in the Sampling Frequency field. Each filter form requires different variables.

Transfer Function

For Transfer Function, you specify the filter by its transfer function representation:

• The Numerator field specifies a variable name or value for the numerator coefficient vector b, which contains m+1 coefficients in descending powers of z.
• The Denominator field specifies a variable name or value for the denominator coefficient vector a, which contains n+1 coefficients in descending powers of z.

State Space

For State Space, you specify the filter by its state-space representation:

The A-Matrix, B-Matrix, C-Matrix, and D-Matrix fields specify a variable name or a value for each matrix in this system.

Zeros, Poles, Gain

For Zeros, Poles, Gain, you specify the filter by its zero-pole-gain representation:

• The Zeros field specifies a variable name or value for the zeros vector z, which contains the locations of m zeros.
• The Poles field specifies a variable name or value for the zeros vector p, which contains the locations of n poles.
• The Gain field specifies a variable name or value for the gain k.

Second Order Sections

For 2nd Order Sections you specify the filter by its second-order section representation:

The SOS Matrix field specifies a variable name or a value for the L-by-6 SOS matrix

whose rows contain the numerator and denominator coefficients b_ik and a_ik of the second-order sections of H(z).

Note    If you import a filter that was not created in SPTool, you can only edit that filter using the Pole/Zero Editor.

Importing Spectra

When you import a power spectral density (PSD), you specify:

• A variable name or a value for the PSD vector in the PSD field
• A variable name or a value for the frequency vector in the Freq. Vector field

The PSD values in the PSD vector correspond to the frequencies contained in the Freq. Vector vector; the two vectors must have the same length.

Accessing Filter Parameters

Loading Variables from the Disk