Waveform Generator

Output waveforms using signal notations

• 

Libraries:
Simulink / Sources

Description

The Waveform Generator block outputs waveforms based on signal notations that you enter in the Waveform Definition table.

This block supports these syntaxes for the signal notations:

• Function syntax — Specify all arguments in the specific order for the signal syntax (see Algorithms).

• Name-value syntax — Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN. For more information, see Algorithms.

This block supports normal, accelerator, and rapid accelerator modes and fast restart.

Supported Operators

Operation	Operator
Absolute value	abs()
Addition	+
Division	/
Multiplication	*
Parentheses	()
Subtraction	-
Unary minus	-

The Waveform block observes the following rules of operator precedence:

1. ( )

2. + - (unary)

3. * /

4. + -

Supported Operations

The Waveform Generator block outputs one signal at a time. You can change this output signal. Express frequency and phase offset parameters in radians. You can also:

• Nest signal notations, for example:

  sin('Amplitude',sin('Amplitude',1,'Frequency',1,'Phase',0),'Frequency',1,'Phase',1)

  

• Reference real scalar variables in the base or model workspace, for example:

  sin('Amplitude',x,'Frequency',y,'Phase',z)

  x, y, and z exist in the base workspace.

For more information on waveforms, see Algorithms.

To quickly determine the response of a system to different types of inputs, you can vary the output signal of the Waveform Generator block while a simulation is in progress.

Examples

Create Interchangeable Variations of Model Components

Create variants of a model component.

• Open Live Script

Switch Between Output Waveforms During Code Execution for Waveform Generator Block

Generate code that enables you to switch between stimulus waveforms during code execution.

(Embedded Coder)

Limitations

• You cannot tune the parameters of a waveform, such as frequency or amplitude, during execution of the code that you generate by using Simulink^® Coder™. Instead, you can generate code that enables you to switch between waveform variants that you specify. For more information, see Switch Between Output Waveforms During Code Execution for Waveform Generator Block (Simulink Coder).

Ports

Output

Port_1 — Generated output signal

scalar | vector

Output signal specified by an entry in the Waveform Definition table.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | bus

Parameters

Main

Output Signal — Waveform for output signal

1 (default) | integer

Select waveform definition to specify the output signal. The number corresponds to the line item in the Waveform Definition table. You can change this parameter while a simulation is running.

Programmatic Use

Block Parameter: SelectedSignal

Type: character vector

Values: scalar

Default: '1'

Waveform Definition — Waveform signal notations

constant | gaussian(mean,variance,seed) | pulse(amplitude,trigger_time,duration) | sawtooth(amplitude,frequence,phase_offset) | sin(amplitude,frequence,phase_offset) | square(amplitude,frequence,phase_offset) | step(step_time,initial_value,final_value)

Enter signal notations in the Waveform Definition table, one waveform definition per line. For syntax details, see Algorithms.

Signal Attributes

The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant.

Output minimum — Minimum output value for range checking

[] (default) | scalar

Lower value of the output range that the software checks.

The software uses the minimum to perform:

• Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.

• Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).

• Automatic scaling of fixed-point data types.

• Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).

Tips

Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	OutMin
Values:	'[]' (default) | scalar in quotes

Output maximum — Maximum output value for range checking

[] (default) | scalar

Upper value of the output range that the software checks.

The software uses the maximum value to perform:

• Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.

• Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).

• Automatic scaling of fixed-point data types.

• Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).

Tips

Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	OutMax
Values:	'[]' (default) | scalar in quotes

Output data type — Specify the output data type

double (default) | Inherit: Inherit via back propagation | single | int8 | int32 | uint32 | int64 | uint64 | fixdt(1,16,2^0,0) | <data type expression> | ...

Choose the data type for the output. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Inherit via back propagation' | 'double' | 'single' | 'int8' | 'uint8' | int16 | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | fixdt(1,16,0) | fixdt(1,16,2^0,0) | fixdt(1,16,2^0,0) | '<data type expression>'

Default: 'double'

Lock output data type setting against changes by the fixed-point tools — Prevent fixed-point tools from overriding data types

off (default) | on

Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor. For more information, see Use Lock Output Data Type Setting (Fixed-Point Designer).

Programmatic Use

Block Parameter: LockScale

Type: character vector

Values: 'off' | 'on'

Default: 'off'

Integer rounding mode — Specify the rounding mode for fixed-point operations

Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero

Choose one of these rounding modes.

Ceiling

Rounds both positive and negative numbers toward positive infinity. Equivalent to the MATLAB^® ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds both positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer round function.

Simplest

Automatically chooses between round toward floor and round toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

Programmatic Use

Block Parameter: RndMeth

Type: character vector

Values: 'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'

Default: 'Floor'

See Also

For more information, see Rounding Modes (Fixed-Point Designer).

Saturate on integer overflow — Method of overflow action

off (default) | on

Specify whether overflows saturate or wrap.

• on — Overflows saturate to either the minimum or maximum value that the data type can represent.

• off — Overflows wrap to the appropriate value that the data type can represent.

For example, the maximum value that the signed 8-bit integer int8 can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer.

• With this parameter selected, the block output saturates at 127. Similarly, the block output saturates at a minimum output value of -128.

• With this parameter cleared, the software interprets the overflow-causing value as int8, which can produce an unintended result. For example, a block result of 130 (binary 1000 0010) expressed as int8 is -126.

Tips

• Consider selecting this parameter when your model has a possible overflow and you want explicit saturation protection in the generated code.

• Consider clearing this parameter when you want to optimize efficiency of your generated code. Clearing this parameter also helps you to avoid overspecifying how a block handles out-of-range signals. For more information, see Troubleshoot Signal Range Errors.

• When you select this parameter, saturation applies to every internal operation on the block, not just the output or result.

• In general, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

Parameter:	SaturateOnIntegerOverflow
Values:	'off' (default) | 'on'

Sample time — Time interval between samples

0.1 (default) | scalar

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See Specify Sample Time for more information.

Programmatic Use

Block Parameter: SampleTime

Type: character vector

Values: scalar

Default: '0.1'

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Algorithms

Enter signal notations in the Waveform Definition table, one waveform definition per line. To add a waveform definition, click Add. The new waveform appears as an empty character vector. The block interprets empty character vectors or white space character vectors as ground.

To remove a waveform definition, click Remove. You can select multiple waveforms using Ctrl+click or Shift+click.

Constant

Constant values can be:

• Numbers

• Workspace variables

  • Scalar, real variables only

• Built-in MATLAB constant, pi

Examples

• 1

• 1.1

• x

• pi

Gaussian Noise

Syntax

gaussian(mean,variance,seed)

gaussian('Mean',mean,'Variance',variance,'Seed',seed)

Input Arguments

• mean — Mean value of the random variable output.

  • Default: 0

• variance — Standard deviation squared of the random variable output.

  • Default: 1

  • Value: Positive constant or positive real scalar variable

• seed — Initial seed value for the random number generator.

  • Default: 0

  • Value: Constant or real scalar variable

Example

gaussian('Mean',0,'Variance',10,'Seed',1)

Pulse

Syntax

pulse(amplitude,trigger_time,duration)

pulse('Amplitude',amplitude,'TriggerTime',trigger_time,'Duration',duration)

Input Arguments

• amplitude — Value of signal when pulse is high.

  • Default: 1

• trigger_time — Elapsed simulation time when signal changes to amplitude, in seconds.

  • Default: 1

  • Value: Constant or real scalar variable

• duration — How long the signal remains at the given amplitude before returning to ground, in seconds.

  • Default: 1

  • Value: Positive constant or positive real scalar variable

Example

pulse('Amplitude',1,'TriggerTime',1,'Duration',1)

Sawtooth

Syntax

sawtooth(amplitude,frequency,phase_offset)

sawtooth('Amplitude',amplitude,'Frequency',frequency,'Phase',phase_offset)

Input Arguments

• amplitude — Sawtooth peak value.

  • Default: 1

• frequency — Waveform frequency, in rad/s.

  • Default: 1

• phase_offset — Horizontal signal shift, based on elapsed simulation time, in seconds.

  • Default: 0

Example

sawtooth('Amplitude',1,'Frequency',1,'Phase',0)

Sine Wave

Syntax

sin(amplitude,frequency,phase_offset)

sin('Amplitude',amplitude,'Frequency',frequency,'Phase',phase_offset)

Input Arguments

• amplitude — Amplitude of sine wave.

  • Default: 1

• frequency — Waveform frequency, in rad/s.

  • Default: 1

• phase_offset — Phase offset, in rads.

  • Default: 0

Examples

sin('Amplitude',1,'Frequency',1,'Phase',0)

To get the cosine waveform:

sin('Amplitude',1,'Frequency',1,'Phase',pi/2)

Square

Syntax

square(amplitude,frequency,phase_delay,duty_cycle)

square('Amplitude',amplitude,'Frequency',frequency,'Phase',phase_delay,...
'DutyCycle',duty_cycle)

Input Arguments

• amplitude — Amplitude of signal.

  • Default: 1

• frequency — Waveform frequency in rad/s.

  • Default: 1

• phase_delay — Horizontal signal shift based on elapsed simulation time, in seconds.

  • Default: 0

• duty_cycle — Percentage of high signal per period (0–100%). The block clips the minimum signal to 0% and the maximum signal to 100%.

  • Default: 50

Example

square('Amplitude',1,'Frequency',1,'Phase',0,'DutyCycle',50)

Step

Syntax

step(step_time,initial_value,final_value)

step('StepTime',step_time,'InitialValue',initial_value,'FinalValue',final_value)

Input Arguments

• step_time — Elapsed simulation time when signal changes from initial value to final value, in seconds.

  • Default: 1

  • Value: Constant or positive real scalar variable.

• initial_value — Value of signal when elapsed simulation time is less than step_time, in seconds.

  • Default: 0

• final_value — Value of signal when elapsed simulation time is greater than or equal to step time, in seconds.

  • Default: 1

Example

step('StepTime',1,'InitialValue',0,'FinalValue',1)

Extended Capabilities

C/C++ Code Generation

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

Not recommended for production code.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2015b