[Note:  The Digital Filter Design Wizard software tool is also available for desiging filters.  However, the example shown below uses the built-in functions included with NEXTWave SPL software.]

Digital Filter Design

Digital filtering is a mathematical system that performs a process on a sampled, discrete time domain signal in order to enhance or reduce certain frequency aspects of that signal.  The frequency response of a digital filter can be analyzed by studying how it reacts when a single unit impulse is applied as an input.  The resulting impulse response is a time domain signal that can be used to visualize how the digital filter will respond to more complex input signals.

The NEXTWave Signal Processing Lab data analysis software provides a wide variety of signal processing functions for use in your application.  It includes powerful digital filter design functions that can be used to construct filters based upon your specific design requirements.  In the example shown below NEXTWave SPL is used to design a digital filter from user-supplied filter design parameters.  The effects of the filter are analyzed by using NEXTWave SPL to generate a single unit impulse as an input to the digital filter, and then observing the resulting behavior of the filter's impulse response in both the time and frequency domain.

Filter Design and Analysis with NEXTWave SPL

In this example NEXTWave SPL is used to design an IIR digital filter, and then analyze its behavior in both the time and frequency domains.  The step-by-step process shown below illustrates the ease of use provided by the NEXTWave SPL programming and analysis environment.  In addition to this impulse response and frequency response example, the digital filter can be easily be designed and applied to a real-world input signal.



Step 1:  Select the Impulse Generator function and add it to the Design Waveform menu ribbon


Step 2:  Select a filter design function and add it to the Design Waveform menu ribbon (for this example, we've chosen an IIR Elliptic design method)

Step 3:  Configure the Impulse Generator function.  For this example, we've set its delay to one sample and are using a framesize of 4096 samples.

Step 4:  Configure the Elliptic filter's design parameters to your desired values.

Step 5:  Select the Single Step control operation to cause NEXTWave SPL to execute a single frame of processing.

Step 6: Observe the filter impulse response in the Time Domain waveform display.

filter impulse response

Step 7: Observe the filter frequency response in the Frequency Domain waveform display.

filter frequency response