DSP Blockset

Step 3 -- Design the Highpass Filter and Select a Filter Structure.   (This step is similar to what you did in the Step 2 -- Design the Lowpass Filter and Select a Filter Structure section.)

1. Place a second Digital Filter Design block from the DSP Blockset Filter Designs library into your model.
2. Set this block's parameters as shown in the following figure.
3. Set the filter structure to direct form FIR transpose (in the Edit menu by selecting Convert Structure...).
4. Click the Magnitude Response button  to view the magnitude response of the filter. (To see the original display, click the Filter Specification button .)

The block now implements a highpass filter with a direct form FIR transpose structure. As the wpass and wstop settings indicate, the filter passes all frequencies greater than or equal to 50% of the Nyquist frequency (half the sampling frequency), and stops frequencies less than or equal to 20% of the Nyquist frequency.

Note that this highpass filter is the "opposite" of the lowpass filter you just designed, in that this filter passes the frequencies stopped by the lowpass filter, and stops the frequencies passed by the lowpass filter. (So, in the model you are building, the lowpass filter should be able to filter out the high-frequency noise output by this highpass filter.)

Step 2 -- Design the Lowpass Filter and Select a Filter Structure

Step 4 -- Set the Rest of the Blocks' Parameters and Connect the Blocks