About Digital Filter Designer

Digital Filter Designer is an integrated application within Advanced Design System's DSP Designer Pro and an option with DSP Designer. It is a specifications-based software tool for designing, simulating, analyzing, and generating coefficients for high-quality digital filters.

Digital Filter Designer enables you to design and analyze a range of digital FIR and IIR filters based upon your specifications. Digital Filter Designer can automatically calculate the least number of taps that meet the desired response specifications, and it can generate both a schematic and a table of coefficients for the designed filter.

The Digital Filter Designer environment has a Main window for entering the filter design specifications and a Status window to display feedback, error, and status messages.
The results of an analysis are automatically displayed in a separate Data Display window that can be configured to plot the frequency response, unit pulse response, unit step response, group delay, poles/zeros, and eye diagram. It can also be used to display the coefficients in a table format.

Coefficients generated by Digital Filter Designer can be used to implement filters and they can be imported into Agilent Ptolemy filter components. Schematics generated by Digital Filter Designer can be added to Advanced Design System schematics.

Main Window

The Main window is displayed each time the application is launched. It displays a set of specifications that may be modified as desired.

In general it may be fruitful to think of the Main window in terms of its three regions, each with its own focus: filter specification area, response specification area, and filter implementation area. While the first two regions are used to design an ideal filter, the third region is used to specify the details for conversion from the ideal filter to a practical filter design.

Note * Disabling conversion reduces the filter design time. So, if your current focus is to generate only an ideal filter design, choose *Options > Disable/Enable Conversion to deactivate the implementation functions.

Menus and Toolbar

The Digital Filter Designer environment provides six menus along with a toolbar that includes buttons for commonly performed tasks.

Menubar

The Digital Filter Designer menubar is made up of the following six menus:

• File
• Design
• Options
• View
• Tools
• Help

The File menu includes the standard Advanced Design System project and file manipulation commands. The Design menu includes commands used to design a filter based upon the displayed specifications and generate a schematic of the filter design. The Options menu provides customizing options along with commands to use alternative design methods. The View menu provides a command to display the filter coefficients and the toolbar. The Help menu provides commands to access online documentation and context-sensitive help.

Toolbar

The Digital Filter Designer toolbar includes frequently used buttons for folder and file manipulation, filter design, filter analysis, and output generation tasks.

The function of each button on the toolbar (going from left to right) is as follows:

• New Project
• Open Project
• Create New Filter Design
• Open Existing Filter Design
• Save Current Filter Design
• Print Current Filter Design
• Import Ideal Coefficients File
• Start Filter Design
• Analyze
• Setup Analysis Parameters
• [Root] Raised Cosine Wizard
• Disable/Enable Conversion
• Generate Schematic
• View Coefficients
• What's This?

Desired Response Tab

The Desired Response tab is used to enter the filter specifications for the desired response. These specifications include the number of passbands and stopbands along with their frequency, amplitude, ripple, and phase values. The numerical format, polynomial or linear, used to describe the amplitude can also be specified.

Weighting Function Tab

The Weighting Function tab is used to define any weighting you may want to specify for the desired response. Weighting specifications include the number of weightbands along with their frequency and magnitude values. The numerical format, polynomial or linear, used for the frequency values can also be specified. The settings in this tab are available when designing an FIR filter using either the Least Squares method or the Equiripple method with a manually specified filter order.

Other Parameters Tab

The Other Parameters tab is used to enter a collection of specifications for transformation, compensation, symmetricity, and windowing parameters when designing certain special (and nonstandard) filters.

Data Display Window

The Data Display window is used to plot and display the data and graphs generated when a filter is designed, a design is analyzed, specifications are plotted, or coefficients are displayed. This window is launched automatically after a filter is designed.

Status Window

The Status window is displayed automatically when Digital Filter Designer is launched. This window is used to display feedback that is divided into two parts: simulation or synthesis messages including errors and warnings, and status or summary messages.