Signal Processing Toolbox Release Notes

Chapter 1
Signal Processing Toolbox 6.0 Release Notes

New Features

This section summarizes the new features and enhancements introduced in the Signal Processing Toolbox.

If you are upgrading from a release earlier than Release 12.1, then you should see Upgrading from an Earlier Release.

This section is organized into the following subsections:

• Digital Filter Objects
• Window Design and Analysis Tool
• Window Objects
• Window Function
• New Windows
• Gaussian Filter Function
• New Analysis Functions
• Improvements to grpdelay
• stepz Function
• digitrevorder Function
• FDATool Enhancements
• FVTool Enhancements
• Demos

Digital Filter Objects

The Signal Processing Toolbox 6.0 adds a new way of creating, viewing, and modifying discrete-time filters using objects. With the new discrete-time filter object, dfilt, you can use object-oriented programming, such as calling constructors to create specific types of filter objects, using get to view the filter properties, and using set to change filter properties. See the dfilt reference page for detailed information on this new object.

Some advantages of using dfilt objects instead of vectors of coefficients [b,a] are:

• The filter's structure is part of the object.
• The filter function can be run on any structure without converting to transfer function form.
• The filter is contained in a single object instead of two vectors. This simplifies passing the filter to another function or GUI.
• freqz, grpdelay, impz, phasez, stepz, and zplane are now overloaded methods. If you pass a dfilt to any of them or if you do not specify any outputs, the filter response is displayed in the Filter Visualization Tool (fvtool), where you can access other filter analyses. If you pass filter coefficients to them, the figure is displayed in a default figure window.
• You can change a filter's characteristics quickly and easily by changing one or more of its properties.
• You can double-click on a dfilt object in the MATLAB Workspace Browser to display the Property Inspector.
• You can highlight a dfilt and right-click in the MATLAB Workspace Browser to launch the Filter Visualization Tool.

Window Design and Analysis Tool

The new Window Design and Analysis Tool (wintool) is a GUI that provides an easy way to design and compare spectral windows. All of the windows provided in the Signal Toolbox are available in wintool. You start wintool from the MATLAB command line. See the wintool reference page for more information.

Window Visualization Tool

A new tool for viewing windows, wvtool, has been added.

Window Objects

A new way of creating, viewing, and modifying windows using objects has been added. The new window object, sigwin, uses object-oriented programming. See Digital Filter Objects above for advantages of using objects. See the sigwin reference page for detailed information on this new object.

Window Function

Using the window function without specifying an input now launches the Window Design and Analysis Tool (wintool).

New Windows

Two new window functions have been added:

• parzenwin computes a Parzen window. This window is also known as a de la Vallé-Poussin window.
• flattopwin computes a Flat Top window.

Gaussian Filter Function

The new function, firgauss designs an FIR Gaussian digital filter.

New Analysis Functions

Three new analysis functions have been added:

• phasedelay - computes the phase delay response of a filter
• phasez - computes the digital phase response of a filter
• zerophase - computes the zero-phase response of a filter. (Previously, this function, using a different syntax, was in the Filter Design Toolbox.)

Improvements to grpdelay

The grpdelay function has been updated to be more accurate for IIR filters with poles/zeros very close to the unit circle. This improvement is also reflected in the Group Delay plot in FDATool and FVTool.

stepz Function

stepz, which is also available as an overloaded dfilt method, is now available from the MATLAB command line. Previously, it was available only in fdatool.

digitrevorder Function

A new function, digitrevorder, allows you to pre-order a vector of filter coefficients.

FDATool Enhancements

• New panel control buttons have been added on the lower left side (in a sidebar) to change the panel from Design Filter to Import Filter. If the Filter Design Toolbox is installed, Set Quantization Parameters and Transform Filter control buttons are also included. If the DSP Blockset is installed, a Realize Model control button is included to create a subsystem filter block in a Simulink model.
• You can specify additional filter design options in the Design panel. These options previously were only available from the command line.
• The Filter Visualization Tool (fvtool), which is launched with the Full View Analysis toolbar button or Analysis->Full View Analysis, can be linked so that it stays synchronized with FDATool. For more information, see the FVTool Enhancements section below.
• The following menu items have been added or updated
• File->Export exports vectors of filter coefficients or a dfilt filter object to the workspace, a text file, or a MAT file.
• File->Export to SPTool exports the current filter to SPTool.
• Edit->Undo now undoes single actions, one at a time. Undo will also undo the design or importing of a filter.
• Edit->Redo redoes the last action.
• Edit->Convert Structure launches a dialog box for converting the underlying filter structure. This dialog box is also available from a context menu (by right-clicking) in the Current Filter Information frame.
• Edit->Convert to Second Order Sections launches a dialog box for converting the filter to Second Order Sections. This dialog box is also available from a context menu (by right-clicking) in the Current Filter Information frame. (The fields in this dialog box previously were part of the Convert Structure dialog box.)
• Edit->Convert to Single Section converts a second order sections filter back to a single section. This option is also available from a context menu (by right-clicking) in the Current Filter Information frame.

• The Convert to Second Order Sections dialog box now limits scaling to Direct form II structures only.

• Analysis->Analysis Parameters sets analysis-specific parameters for the filter responses. You can also access this from the context menu. You can now save your preferred Analysis Parameters by clicking Save as Default in the Analysis Parameters dialog box.
• Analysis->Sampling Frequency sets the sampling frequency for the current filter.
• The Filter menu has been removed. You can access all items previously on this menu from the sidebar and Edit menu.
• Context menus, which you access by right-clicking, are included for setting the units, changing the display, setting the sampling frequency, or accessing the Analysis Parameters on the response plots and labels.
• The Pole/Zero Plot can now display the number of poles /zeros in cases where multiple poles/zeros occur at a single point.
• A new filter design method--Maximally flat--has been added. Other new methods have also been added in the Filter Design Toolbox,
• To perform zero-phase analysis, right-click on the y-axis label of a Magnitude plot to display the context menu and select Zero-Phase, or select it in the Analysis Parameters dialog box. To display the corresponding phase plot, select Continuous Phase from the Phase context menu.
• Data markers have been enhanced so they are now movable.
• The Current Filter Information frame has been updated. The Convert Structure button has been removed. To convert a structure, select Convert Structure from the right-click context menu or from the Edit menu.

FVTool Enhancements

• FVTool can be synchronized with FDATool with the Activate FDAToolLink toolbar button. When activated, any changes made to the filter in FDATool are immediately reflected in FVTool.
• File->FDAToolLink sets the mode for FDAToolLink. Replace current filter removes the filter in FVTool and replaces it with the new FDATool filter. Add new filter adds the FDATool filter to the current filter in FVTool so that multiple filters can be displayed and compared. You can also set the mode using the Set Link mode toolbar button.
• The Edit and Insert menus have been customized to FVTool and irrelevant menu items have been removed.
• A new Tools menu, which includes edit plot and zoom options, has been added.
• If the Filter Design Toolbox is installed, a new analysis method, Noise Loading Method, has been added to the Analysis menu. Refer to the Filter Design Toolbox documentation for more information.
• Context menus, which you access by right-clicking, are included for setting the units, changing the display, or accessing the Analysis Parameters on the response plots and labels.
• You can now save your preferred Analysis Parameters by clicking Save as Default in the Analysis Parameters dialog box.
• You can name the filter and specify the filter's sampling frequency with Sampling Frequency on the Analysis menu or by selecting Sampling Frequency from the context menu. If you have more than one filter, you can specify a different name and sampling frequency for each filter.
• To perform zero-phase analysis, right-click on the y-axis label of a Magnitude plot to display the context menu and select Zero-Phase, or select it in the Analysis Parameters dialog box. To display the corresponding phase plot, select Continuous Phase from the Phase context menu.

Demos

You can now launch the Window Visualization Tool (wvtool) from the Vector Transition demo (windtrandemo) to view the selected window.

A new Spectral Estimation demo (psddemo) has been added.

A new digital filter object demo (dfiltdemo) has been added.

The spectrogram demo (specgramdemo) has been enhanced with additional audio playback and visualization options.

Signal Processing Toolbox Release Notes

Major Bug Fixes