Signal Processing Toolbox

Setting the Filter Design Specifications

The filter design specifications that you can set vary according to filter type and design method. For example, to design a bandpass filter, you can enter:

• Frequency specifications
• Magnitude specifications
• Filter order

The display region illustrates filter specifications when you select Filter Specifications from the Analysis menu.

Bandpass Filter Frequency Specifications

For a bandpass filter, you can set:

• Units of frequency:
• Hz
• kHz
• MHz
• Normalized (0 to 1)
• Sampling frequency
• Passband frequencies
• Stopband frequencies

You specify the passband with two frequencies. The first frequency determines the lower edge of the passband, and the second frequency determines the upper edge of the passband.

Similarly, you specify the stopband with two frequencies. The first frequency determines the upper edge of the first stopband, and the second frequency determines the lower edge of the second stopband.

For this example:

• Keep the units in Hz (default).
• Set the sampling frequency (Fs) to 2000 Hz.
• Set the end of the first stopband (Fstop1) to 200 Hz.
• Set the beginning of the passband (Fpass1) to 300 Hz.
• Set the end of the passband (Fpass2) to 700 Hz.
• Set the beginning of the second stopband (Fstop2) to 800 Hz.

Bandpass Filter Magnitude Specifications

For a bandpass filter, you can specify the following magnitude response characteristics:

• Units for the magnitude response (dB or linear)
• Passband ripple
• Stopband attenuation

For this example:

• Keep the units in dB (default).
• Set the passband ripple (Apass) to 0.1 dB.
• Set the stopband attenuation for both stopbands (Astop1, Astop2) to 75 dB.

Choosing a Filter Design Method

Filter Order