Using the FDATool in Digital Filter Applications - 2025.2 English

Using the FDATool in Digital Filter Applications - 2025.2 English - UG1483

Vitis Model Composer User Guide (UG1483)

Document ID

UG1483

Release Date

2025-11-20

Version

2025.2 English

The FDATool block defines the filter order and coefficients. The HDL blocks implement a filter. The Tools library in the HDL Blockset contains the FDATool block.

Figure 1. FDATool Block

A simple Model Composer model, shown in the following figure, illustrates a standard FIR filter design using the FDATool and digital FIR filter block.

The design uses two sine wave sources. It adds them together and passes them separately through two low-pass filters.

You can implement the first filter using the AMD HDL blockset. It is a digital low pass filter implemented using the Digital FIR filter block.
The second filter is a reference filter. This is a low pass filter. You can implement this using a Direct-form FIR structure.

The frequency response of both filters visualized in Spectrum Analyzer block.

Figure 2. Spectrum Analyzer Block

You can use the AMD version of the FDAtool to define the coefficients of the low-pass filter to eliminate high-frequency noise. The filter configuration parameters like Response Type, Filter Order, Frequency Specification, and Magnitude Specification can be modified from the Properties Editor of the FDATool. This is shown in the following figure.

Figure 3. Filter Configuration

The Design Filter option at the bottom of the tool window allows you to find out the filter order and observe the Magnitude Response. You can also view the Phase Response, Impulse Response, Coefficients, and more by selecting the appropriate icon at the top-right of the window. You can display the filter coefficients in the MATLAB® workspace by typing the following:

>> xlfda_numerator('FDATool')

The following functions help you find the maximum and minimum coefficient values to adequately specify the coefficient width and binary point:

>> max(xlfda_numerator('FDATool'))
>> min(xlfda_numerator('FDATool'))

Now, you can associate the filter parameters of the FDATool instance with the Digital FIR filter instance.

Figure 4. Digital FIR Filter

The AMD Filter response can be viewed and compared with the Simulink® response using the Spectrum Analyzer.

Figure 5. Spectrum Analyzer

Note: The frequency response results of Model Composer (right side), shown above, differs slightly with the original design (left side). This is due to the quantization and sampling effect inherent when a continuous time system is described in discrete time hardware.

For a complete example along with steps to use the FDATool, refer to the Vitis Model Composer Tutorials.