Example with Default Parameters :: Special Filters (Communications Toolbox)

Communications Toolbox

Example with Default Parameters

For example, typing simply

hilbiir

plots the impulse response of a fourth-order digital Hilbert transform filter having a 1-second group delay. The sample time is 2/7 seconds. In this particular design, the tolerance index is 0.05. The plot also displays the impulse response of the ideal Hilbert transform filter having a 1-second group delay. The plot is in the figure in Noncausality and the Group Delay Parameter.

To compute this filter's transfer function, use the command below.

[num,den] = hilbiir

num =

   -0.3183   -0.3041   -0.5160   -1.8453    3.3105


den =

    1.0000   -0.4459   -0.1012   -0.0479   -0.0372

Here, the vectors num and den contain the coefficients of the numerator and denominator, respectively, of the transfer function in ascending order of powers of z^-1.

The commands in this section use the function's default parameters. You can also control the filter design by specifying the sample time, group delay, bandwidth, and tolerance index. The reference entry for hilbiir explains these parameters. The group delay is also mentioned above in Noncausality and the Group Delay Parameter.

Designing Hilbert Transform Filters

Filtering with Raised Cosine Filters