Second-Order Low-Pass Filter

Models, in the continuous-time domain, a second-order low-pass filter characterized by a cut-off frequency and a damping ratio.

Library

Description

The Second-Order Low-Pass Filter block models, in the continuous-time domain, a second-order low-pass filter characterized by a cut-off frequency and a damping ratio. This block supports vector input signals and can have its filter Cut-off frequency, Damping ratio and Initial condition parameters set either internally using its dialog box or externally using input ports. The filtered output is always continuous even after any parameter change (e.g., Cut-off frequency and/or Damping ratio).

The transfer function for this filter is shown below:

where ω_n is the cut-off frequency and ζ is the damping ratio.

Input Ports

x

The input signal to the second-order low-pass filter.

wn

This port appears when the Source of parameters is set to External (input ports), and provides the cut-off frequency (in radians per second, i.e., rad/s) of the second-order low-pass filter.

zt

This port appears when the Source of parameters is set to External (input ports), and provides the damping ratio of the second-order low-pass filter.

x0

This port appears when the Source of parameters is set to External (input ports), and provides the input signal initial condition to the second-order low-pass filter.

Output Ports

y

The (filtered) output signal from the second-order low-pass filter.

yd

The time-derivative of the output signal from the second-order low-pass filter.

Data Type Support

The block outputs are of type double.

Parameters and Dialog Box

Source of parameters

The source of the continuous filter Cut-off frequency, Damping ratio and Initial condition parameters is determined by this field to be to be Internal (dialog parameter) or External (block inputs).

Cut-off frequency (rad/s) (tunable online)

This parameter sets the cut-off frequency (in radians per second, i.e., rad/s) of the second-order low-pass filter.

Damping ratio (tunable online)

This parameter sets the damping ratio of the second-order low-pass filter.

Initial condition (tunable offline)

This parameter sets the initial condition of the second-order low-pass filter.

Targets

See Also

• Discrete Second-Order Low-Pass Filter block

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