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The procedures are very similar to those explained in

Importing a Signal into SPTool for loading variables from the workspace

Loading Variables from the Disk for loading variables from your disk

When you import filters, first select the appropriate filter
form from the **Form** list. SPTool does not currently
support the import of filter objects.

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.

For `Transfer Function`

, you specify the filter
by its transfer function representation:

$$H(z)=\frac{B(z)}{A(z)}=\frac{b(1)+b(2){z}^{-1}+\cdots +b(m+1){z}^{-m}}{a(1)+a(2){z}^{-1}+\cdots +a(n+1){z}^{-n}}$$

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*.

For `State Space`

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

$$\begin{array}{c}\dot{x}=Ax+Bu\\ y=Cx+Du\end{array}$$

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

For `Zeros`

, `Poles`

, `Gain`

,
you specify the filter by its zero-pole-gain representation:

$$H(z)=\frac{Z(z)}{P(z)}=k\frac{(z-z(1))(z-z(2))\cdots (z-z(m))}{(z-p(1))(z-p(2))\cdots (z-p(n))}$$

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*.

For `2nd`

`Order`

`Sections`

you
specify the filter by its second-order section representation:

$$H(z)={\displaystyle \prod _{k=1}^{L}{H}_{k}(z)={\displaystyle \prod _{k=1}^{L}\frac{{b}_{0k}+{b}_{1k}{z}^{-1}+{b}_{2k}{z}^{-2}}{1+{a}_{1k}{z}^{-1}+{a}_{2k}{z}^{-2}}}}$$

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

$$\text{sos}=\left[\begin{array}{cccccc}{b}_{01}& {b}_{11}& {b}_{21}& 1& {a}_{11}& {a}_{21}\\ {b}_{02}& {b}_{12}& {b}_{22}& 1& {a}_{12}& {a}_{22}\\ \vdots & \vdots & \vdots & \vdots & \vdots & \vdots \\ {b}_{0L}& {b}_{1L}& {b}_{2L}& 1& {a}_{1L}& {a}_{2L}\end{array}\right]$$

whose rows contain the numerator and denominator coefficients *b _{ik}* and

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

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

A variable name or a value for the PSD vector in the

**PSD**fieldA 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.

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