Release Notes for Release 12.1

Chapter 15
Filter Design Toolbox 2.1 Release Notes

New Features

This section introduces the new features and enhancements added in the Filter Design Toolbox 2.1 since Filter Design Toolbox 2.0 (Release 12).

For information about Filter Design Toolbox features that are incorporated from recent releases, see the Release Notes for Release 12.

New Adaptive Filtering Functions

The Filter Design Toolbox 2.1 includes these new filter design functions:

• adaptkalman -- Use a Kalman filtering algorithm in an adaptive filter role
• adaptlms - Use an LMS-based adaptive algorithm in an adaptive filter role
• adaptnlms - Use a normalized LMS-based adaptive algorithm in an adaptive filter role
• adaptrls - Use an RLS-based adaptive algorithm in an adaptive filter role
• adaptsd - Use the sign-data variant of the LMS-based adaptive algorithm in an adaptive filter role
• adaptse - Use the sign-error variant of the LMS-based adaptive algorithm in an adaptive filter role
• adaptss -- Use the sign-sign variant of the LMS-based adaptive algorithm in an adaptive filter role

To support you when you use these new functions, the Toolbox includes corresponding functions for initializing the associated adaptive filter algorithm.

• initkalman -- Initialize the input argument s for the Kalman-based algorithm adaptive filter function
• initlms -- Initialize the input argument s for the LMS-based adaptive filter function
• initnlms -- Initialize the input argument s for the normalized LMS-based adaptive filter function
• initrls -- Initialize the input argument s for the RLS-based adaptive filter function
• initsd -- Initialize the input argument s for the sign-data variant of the LMS-based adaptive filter function
• initse -- Prepare the input arguments for the sign-error variant of the LMS-based adaptive filter function
• initss -- Prepare the input arguments for the sign-sign variant of the LMS-based adaptive filter function

New FIR Filter Design Functions

In addition to the new adaptive filtering capabilities, this version of the toolbox has four new filter design functions.

• firhalfband -- Design Lth-band filters where L=2. About half of the filter coefficients are zero so the filters are very efficient to calculate
• firminphase -- Calculate the minimum-phase FIR spectral factor of a linear-phase FIR filter
• firnyquist -- Design lowpass filters with certain specified coefficients in the transfer functions set to zero by design
• ifir -- Design an interpolated FIR filter

FDATool includes Halfband and Nyquist entries under Filter Type so you can design and analyze these kinds of filters within FDATool.

New Filter Transformation Functions

The Filter Design Toolbox 2.1 includes several new filter transformation functions. Each transformation maintains the ripple characteristics and passband/stopband shapes of the source filter while transforming to the new specification.

• firlp2lp -- Transforms lowpass FIR filters to lowpass FIR filters with different passband width or cutoff specifications
• firlp2hp -- Transforms lowpass FIR filters to highpass FIR filters
• iirlp2bp -- Transforms lowpass IIR filters to bandpass IIR filters
• iirlp2bs -- Transforms lowpass IIR filters to bandstop IIR filters
• iirlp2hp -- Transforms lowpass IIR filters to highpass IIR filters
• iirlp2lp -- Transforms lowpass IIR filters to lowpass IIR filters

The new Transformations option (refer to the next entry in this section) in FDATool provides access to these transformations from the GUI.

Transformations Option in FDATool

When you use Filter Design and Analysis Tool (FDATool) with Filter Design Toolbox 2.1, the Toolbox adds a new menu to the FDATool menu bar. Named Transformations, the new selection provides direct access to the new FIR and IIR filter transformation functions added to the Toolbox in this release (refer to New Filter Transformation Functions). Transformations appears as shown in this figure only when you have installed the Filter Design Toolbox.

With this new option, FIR and IIR filters whose characteristics are particularly valuable become the sources for other FIR and IIR filters that share the same desirable features in a different passband configuration. Transforming a filter saves you from repeating the filter design process. For more information, refer to Transforming Filters in your Filter Design Toolbox User's Guide.

In the figure, the Targets option is available only when you have the Developer's Kit for Texas Instruments DSP installed.

New Analysis Method

Filter Design Toolbox 2.1 includes one new analysis method -- zerophase -- that returns the zero-phase response of a linear-phase FIR filter.

[hr,w] = zerophase(b), and the other available syntax options for zerophase, returns the zero-phase response hr and the frequency vector w (in rad/sample) at which hr is computed, given a linear-phase FIR filter b. The zero-phase response is evaluated at 512 equally spaced points on the upper half of the unit circle.

Note that the zero-phase response is always real, but it is not equivalent to the magnitude response. In particular, the zero-phase response can be negative; the magnitude response is always positive.

New Context-Sensitive Help for Quantization

FDATool Quantization mode now includes context sensitive or What's This? help. For each option on the Set Quantization Parameters page, right-click to use the What's This? option to open a brief text description of the option.

Known Software Problems

Platform Limitations for HP 10.2