Signal Generator

Generate various waveforms

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Libraries:
Simulink / Sources

Description

Supported Operations

The Signal Generator block can produce one of four different waveforms:

• sine

• square

• sawtooth

• random

You can express signal parameters in hertz or radians per second. Using default parameter values, you get one of the following waveforms:

Waveform	Scope Output
Sine wave
Square wave
Sawtooth wave
Random wave

A negative Amplitude parameter value causes a 180-degree phase shift. You can generate a phase-shifted wave at other than 180 degrees in many ways. For example, you can connect a Clock block signal to a MATLAB Function block and write the equation for the specific wave.

You can vary the output settings of the Signal Generator block while a simulation is in progress to determine quickly the response of a system to different types of inputs.

The Amplitude and Frequency parameters determine the amplitude and frequency of the output signal. The parameters must be of the same dimensions after scalar expansion. If you clear the Interpret vector parameters as 1-D check box, the block outputs a signal of the same dimensions as the Amplitude and Frequency parameters (after scalar expansion). If you select the Interpret vector parameters as 1-D check box, the block outputs a vector (1-D) signal if the Amplitude and Frequency parameters are row or column vectors, that is, single-row or column 2-D arrays. Otherwise, the block outputs a signal of the same dimensions as the parameters.

Solver Considerations

If your model uses a fixed-step solver, Simulink^® uses the same step size for the entire simulation. In this case, the Signal Generator block output provides a uniformly sampled representation of the ideal waveform.

If your model uses a variable-step solver, Simulink might use different step sizes during the simulation. In this case, the Signal Generator block output does not always provide a uniformly sampled representation of the ideal waveform. To ensure that the block output is a uniformly sampled representation, add a Hit Crossing block directly downstream of the Signal Generator block. These models show the difference in Signal Generator block output with and without the Hit Crossing block.

Model That Uses a Variable-Step Solver	Signal Generator Block Output

Examples

Inverted Pendulum with Animation

Use Simulink® to model and animate an inverted pendulum system. An inverted pendulum has its center of mass above its pivot point. To stably maintain this position, the system implements control logic to move the pivot point below the center-of mass as the pendulum starts to fall. The inverted pendulum is a classic dynamics problem used to test control strategies.

• Open Model

Aircraft Longitudinal Flight Control

Model flight control for the longitudinal motion of an aircraft using first-order linear approximations.

• Open Model

Double Spring Mass System

Model a double spring-mass-damper system with a periodically varying forcing function. The model uses an S-Function block to animate the mass system during simulation. In the system, the only sensor is attached to the mass on the left, and the actuator is attached to the mass on the left. The example uses state estimation and linear-quadratic regulator (LQR) control.

• Open Model

Ports

Output

Port_1 — Generated output signal

scalar | vector | matrix

Output signal specified as one of these waveforms.

• sine

• square

• sawtooth

• random

Data Types: double

Parameters

Wave form — Wave form to generate

sine (default) | square | sawtooth | random

Specify the wave form.

Programmatic Use

Block Parameter: WaveForm

Type: character vector

Values: 'sine' | 'square' | 'sawtooth' | 'random'

Default: 'sine'

Time (t) — Source of time variable

Use simulation time (default) | Use external signal

Specify whether to use simulation time or an external signal as the source of values for the waveform time variable. If you specify an external source, the block displays an input port for connecting the source.

Programmatic Use

Block Parameter: TimeSource

Type: character vector

Values: 'Use simulation time' | 'Use external signal'

Default: 'Use simulation time'

Amplitude — Signal amplitude

1 (default) | scalar | vector | matrix

Specify the amplitude of the generated waveform.

Programmatic Use

Block Parameter: Amplitude

Type: character vector

Values: real scalar

Default: '1'

Frequency — Signal frequency

1 (default) | scalar | vector | matrix

Specify the frequency of the generated waveform.

Programmatic Use

Block Parameter: Frequency

Type: character vector

Values: real scalar

Default: '1'

Units — Signal units

rad/sec (default) | Hertz

Specify the signal units as Hertz or rad/sec.

Programmatic Use

Block Parameter: Units

Type: character vector

Values: 'rad/sec' | 'Hertz'

Default: 'rad/sec'

Interpret vector parameters as 1-D — Treat vectors as 1-D

on (default) | off

Select this check box to output a vector of length N if the Constant value parameter evaluates to an N-element row or column vector.

• When you select this check box, the block outputs a vector of length N if the Constant value parameter evaluates to an N-element row or column vector. For example, the block outputs a matrix of dimension 1-by-N or N-by-1.

• When you clear this check box, the block does not output a vector of length N if the Constant value parameter evaluates to an N-element row or column vector.

Programmatic Use

Block Parameter: VectorParams1D

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Block Characteristics

Data Types	double
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Cannot be used inside a triggered subsystem hierarchy.

These blocks do not reference absolute time when configured for sample-based operation. In time-based operation, they depend on absolute time.

Version History

Introduced before R2006a