This version (09 Jan 2021 00:58) was approved by Robin Getz.The Previously approved version (21 Jan 2013 19:58) is available.Diff

General (2nd-Order / Lookup)

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The General (2nd-Order / Lookup) block gives access to a wide variety of 2nd-order IIR (infinite impulse response) filter algorithms. See General 2nd-Order Filters (in Algorithm Information) for details about the algorithms driving these blocks.

The filters available are:

  • Tone
  • Peaking
  • General LP/HP
  • Butterworth LP/HP
  • Bessel LP/HP
  • Chebyshev LP/HP

This block is implemented by a double-precision biquad filter that has multiple sets of coefficients in tables on the DSP. To select curves (lookup), use an Index Lookup Table, a Counter block, or a DC Input block in your design and connect it to the red pin. Using the GPIO blocks you could control the selected responses with a knob, rotary encoder or button.

To open the Filter Control Window:

Click the icon button:. The curve is defined using the Tone Control window (shown below).

Enter the number of curves desired in the # Curves field. Enter Boosts, (overall) Gain, and Q in their fields. Enter the desired cutoff or center (peaking filters) frequency in the Frequency fields. Other parameters to enter will vary with filter type.

The variety and range of filters are remarkable, as can be seen from the following examples:

Note: For n curves, the selected index should not exceed n - 1, i.e., the index range is 0 to n - 1. If you select an n th curve, misbehavior or errors may result.

resources/tools-software/sigmastudio/toolbox/filters/general2ndorderlookup.txt · Last modified: 09 Jan 2021 00:57 by Robin Getz