This version (23 Jun 2020 22:13) was approved by Joshua Berlin.The Previously approved version (15 Nov 2012 17:40) is available.

State Variable

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The State-Variable block allows for simultaneous access to three different filter types: lowpass, highpass, and bandpass.

Set the center frequency in the Freq (Hz) field or by dragging the arrows. For examples and details, see Filters Example.

To have external control over Q from the block, refer to the State-Variable (Q input) Filter.

To have external control over Q and F from the block, refer to the State-Variable (Q/F input) Filter.

The three output pins let you choose among LP, HP, BP filters. The nature of this algorithm is to compute the coefficients for all filter types, giving you access to all of the filters simultaneously.

Parameter Calculation

The following describes how the DSP uses input parameters to calculate the filter outputs.

$D(z) = 1 + (f^2 + q f - 2) z^{-1} + (1 - q f) z^(-2)$

$H_{BPF}(z) = {f - f z^{-1} } / {D(z)}$ $H_{HPF}(z) = {1 - 2z^{-1} + z^{-2}} / {D(z)}$ $H_{LPF}(z) = {f^2 z^{-1}} / {D(z)}$

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Analog Devices Wiki

State Variable

Parameter Calculation

Analog Devices Wiki

State Variable

Parameter Calculation

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