Sine Wave
Generate continuous or discrete sine wave
 Library:
DSP System Toolbox / Sources
DSP System Toolbox HDL Support / Sources
Description
The Sine Wave block generates a multichannel real or complex sinusoidal signal, with independent amplitude, frequency, and phase in each output channel. The block supports floating point and signed fixedpoint data types.
The block generates a real sinusoidal signal when you set the Output
complexity parameter to Real
. The real
sinusoidal output is defined by an expression of the type
$$y=A\mathrm{sin}\left(2\pi ft+\varphi \right)$$
where you specify A in the Amplitude parameter, f in hertz in the Frequency parameter, and ϕ in radians in the Phase offset parameter.
The block generates a complex exponential signal when you set the Output
complexity parameter to Complex
. This complex
exponential signal is defined by an expression of the type
$$y=A{e}^{j(2\pi ft+\varphi )}=A\left\{\mathrm{cos}\left(2\pi ft+\varphi \right)+j\mathrm{sin}\left(2\pi ft+\varphi \right)\right\}$$
Generating Multichannel Outputs
For both real and complex sinusoids, the Amplitude, Frequency, and Phase offset parameter values (A, f, and ϕ) can be scalars or lengthN vectors, where N is the desired number of channels in the output. When you specify at least one of these parameters as a lengthN vector, scalar values specified for the other parameters are applied to every channel.
For example, to generate the threechannel output containing the following real sinusoids, set the block parameters as shown:
$$y=\{\begin{array}{cc}\mathrm{sin}\left(2000\pi t\right)& \text{(channel1)}\\ 2\mathrm{sin}\left(1000\pi t\right)& \text{(channel2)}\\ 3\mathrm{sin}\left(500\pi t+\frac{\pi}{2}\right)& \text{(channel3)}\end{array}\text{}$$
Output complexity =
Real
Amplitude =
[1 2 3]
Frequency =
[1000 500 250]
Phase offset =
[0 0 pi/2]
Ports
Output
Port_1
— Sinusoidal signal
scalar  vector  matrix
Output a sinusoidal signal as a scalar or vector. For more information about output complexity, see Description. For information about multichannel support, see Generating Multichannel Outputs.
Tip
To output fixedpoint data types, you must set Sample
mode to Discrete
and
Computation method to Table
lookup
.
Data Types: single
 double
 fixed point
Complex Number Support: Yes
Parameters
Main
Amplitude
— Amplitude of sine waves
1
(default)  scalar  vector
A lengthN vector containing the amplitudes of the sine waves in each of N output channels, or a scalar to be applied to all N channels. The vector length must be the same as that specified for the Frequency and Phase offset parameters.
Tip
This parameter is tunable (Simulink) only when the Computation
method is Trigonometric
fcn
or
Differential
.
Tunable: Yes
Frequency (Hz)
— Frequency of each sine wave
100
(default)  scalar  vector
A lengthN vector containing frequencies, in hertz, of the sine waves in each of N output channels, or a scalar to be applied to all N channels. The vector length must be the same as that specified for the Amplitude and Phase offset parameters. You can specify positive, zero, or negative frequencies.
Tip
This parameter is tunable (Simulink) when you set either:
Sample mode to
Continuous
.Sample mode to
Discrete
and Computation method toTrigonometric fcn
.
Tunable: Yes
Phase offset (rad)
— Phase offset
0
(default)  scalar  vector
A lengthN vector containing the phase offsets, in radians, of the sine waves in each of N output channels, or a scalar to be applied to all N channels. The vector length must be the same as that specified for the Amplitude and Frequency parameters.
Tip
This parameter is tunable (Simulink) when you set either:
Sample mode to
Continuous
.Sample mode to
Discrete
and Computation method toTrigonometric fcn
.
Tunable: Yes
Sample mode
— Continuous or discrete sampling mode
Discrete
(default)  Continuous
Specify the sampling mode as Continuous
or
Discrete
:
Continuous
In continuous mode, the sinusoid in the ith channel, y_{i}, is computed as a continuous function,
$$\begin{array}{ll}{y}_{i}={A}_{i}\mathrm{sin}\left(2\pi {f}_{i}t+{\varphi}_{i}\right)\hfill & \text{(real)}\hfill \\ \begin{array}{l}\\ \text{or}\\ \end{array}\hfill & \hfill \\ {y}_{i}={A}_{i}{e}^{j\left(2\pi {f}_{i}t+{\varphi}_{i}\right)}\hfill & \text{(complex)}\hfill \end{array}$$
and the block's output is continuous. In this mode, the block operates the same as the Simulink^{®} Sine Wave block with Sample time set to
0
. This mode offers high accuracy, but requires trigonometric function evaluations at each simulation step, which is computationally expensive. Also, because this method tracks absolute simulation time, a discontinuity will eventually occur when the time value reaches its maximum limit.Note also that many DSP System Toolbox™ blocks do not accept continuoustime inputs.
Discrete
In discrete mode, the block can generate discretetime output by directly evaluating the trigonometric function, by table lookup, or by a differential method. For more information on these computation methods, see Algorithms.
Output complexity
— Real or complex waveform
Real
(default)  Complex
The type of waveform to generate: Real
specifies a real sine wave, Complex
specifies
a complex exponential.
Computation method
— Method for computing discretetime sinusoids
Trigonometric fcn
(default)  Table lookup
 Differential
The method by which discretetime sinusoids are generated:
Trigonometric fcn
, Table
lookup
, or Differential
.
For more information on each of the available options, see Algorithms.
Dependencies
This parameter is only visible when you set the Sample
mode to Discrete
.
Note
To generate fixedpoint sinusoids, you must set the
Computation method to
Table lookup
.
Optimize table for
— Optimize for speed or memory
Speed
(default)  Memory
Optimizes the table of sine values for
Speed
or
Memory
. When optimized for speed, the
table contains k elements, and when optimized for
memory, the table contains k/4 elements, where
k is the number of input samples in one full
period of the sine wave.
Dependencies
This parameter is only visible when you set the
Computation method parameter to
Table lookup
.
Sample time
— Sample period
1/1000
(default)  scalar
The period with which the sine wave is sampled, T_{s}, as a finite scalar, greater than zero. The output frame period of the block is MT_{s}, where you specify M in the Samples per frame parameter.
Dependencies
To enable this parameter, set Sample mode to
Discrete
.
Samples per frame
— Samples per frame
1
(default)  positive integer
The number of consecutive samples from each sinusoid to buffer into the output frame, M, specified as a positive scalar integer. This parameter is not tunable.
The block output is an MbyN matrix with frame period MT_{s}, where you specify T_{s} in the Sample time parameter.
Dependencies
To enable this parameter, set Sample mode to
Discrete
.
Resetting states when reenabled
— State behavior inside enabled subsystems
Restart at time
zero
(default)  Catch up to simulation time
This parameter determines the behavior of the Sine Wave
block when an enabled subsystem is reenabled. The block can either reset
itself to its starting state (Restart at time
zero
), or resume generating the sinusoid based on the
current simulation time (Catch up to simulation
time
).
Dependencies
This parameter only applies when the Sine Wave
block is located inside an enabled subsystem and the
States when enabling parameter of the
Enable (Simulink) block is set
to reset
.
Data Types
Output data type
— Output data type
double
(default)  single
 fixdt(1,16)
 fixdt(1,16,0)
 <data type expression>
 Inherit:Inherit via back
propagation
Select how you would like to specify the data type properties of the Output data type. You can choose:
Inherit
— Lets you specify a rule for inheriting a data type, for example,Inherit: Inherit via back propagation
Built in
— Lets you specify a built in data type, for example,double
Fixed point
— Lets you specify the fixedpoint attributes of the data type.Expression
— Lets you specify an expression that evaluates to a valid data type, for example,fixdt(1,16)
Block Characteristics
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 

Algorithms
When you select Discrete
from the Sample
mode parameter, the secondary Computation method
parameter provides three options for generating the discrete sinusoid:
Trigonometric fcn
, Table
lookup
, and Differential
.
Trigonometric Fcn
The trigonometric function method computes the sinusoid in the ith channel, y_{i}, by sampling the continuous function
$$\begin{array}{ll}{y}_{i}={A}_{i}\mathrm{sin}\left(2\pi {f}_{i}t+{\varphi}_{i}\right)\hfill & \text{(real)}\hfill \\ \begin{array}{l}\\ \text{or}\\ \end{array}\hfill & \hfill \\ {y}_{i}={A}_{i}{e}^{j\left(2\pi {f}_{i}t+{\varphi}_{i}\right)}\hfill & \text{(complex)}\hfill \end{array}$$
with a period of T_{s}, where you specify
T_{s} in the Sample
time parameter. This mode of operation has the same benefits and
liabilities as the Continuous
sample mode.
At each sample time, the block evaluates the sine function at the appropriate time value within the first cycle of the sinusoid. By constraining trigonometric evaluations to the first cycle of each sinusoid, the block avoids the imprecision of computing the sine of very large numbers, and eliminates the possibility of discontinuity during extended operations (when an absolute time variable might overflow). This method therefore avoids the memory demands of the table lookup method at the expense of many more floatingpoint operations.
Table Lookup
The table lookup method precomputes the unique samples of every output sinusoid at the start of the simulation, and recalls the samples from memory as needed. Because a table of finite length can only be constructed when all output sequences repeat, the method requires that the period of every sinusoid in the output be evenly divisible by the sample period. That is, 1/(f_{i}T_{s}) = k_{i} must be an integer value for every channel i = 1, 2, ..., N.
When the Optimize table for parameter is set to
Speed
, the table constructed for each channel
contains k_{i} elements. When the
Optimize table for parameter is set to
Memory
, the table constructed for each channel
contains k_{i}/4 elements.
For long output sequences, the table lookup method requires far fewer floatingpoint operations than any of the other methods, but can demand considerably more memory, especially for high sample rates (long tables). This method is recommended for models that are intended to emulate or generate code for DSP hardware, and that therefore must be optimized for execution speed.
Note
The lookup table for this block is constructed from doubleprecision
floatingpoint values. Thus, when you use the Table
lookup
computation mode, the maximum amount of precision you
can achieve in your output is 53 bits. Setting the word length of the
Output or Userdefined data type
to values greater than 53 bits does not improve the precision of your
output.
Tip
To generate fixedpoint sinusoids, you must select Table
Lookup
.
Differential
The differential method uses an incremental algorithm. This algorithm computes the output samples based on the output values computed at the previous sample time (and precomputed update terms) by using the following identities.
$$\begin{array}{l}\mathrm{sin}\left(t+{T}_{s}\right)=\mathrm{sin}\left(t\right)\mathrm{cos}\left({T}_{s}\right)+\mathrm{cos}\left(t\right)\mathrm{sin}\left({T}_{s}\right)\\ \mathrm{cos}\left(t+{T}_{s}\right)=\mathrm{cos}\left(t\right)\mathrm{cos}\left({T}_{s}\right)\mathrm{sin}\left(t\right)\mathrm{sin}\left({T}_{s}\right)\end{array}$$
The update equations for the sinusoid in the ith channel, y_{i}, can therefore be written in matrix form as
$$\left[\begin{array}{c}\mathrm{sin}\left\{2\pi {f}_{i}\left(t+{T}_{s}\right)+{\varphi}_{i}\right\}\\ \mathrm{cos}\left\{2\pi {f}_{i}\left(t+{T}_{s}\right)+{\varphi}_{i}\right\}\end{array}\right]=\left[\begin{array}{cc}\mathrm{cos}\left(2\pi {f}_{i}{T}_{s}\right)& \mathrm{sin}\left(2\pi {f}_{i}{T}_{s}\right)\\ \mathrm{sin}\left(2\pi {f}_{i}{T}_{s}\right)& \mathrm{cos}\left(2\pi {f}_{i}{T}_{s}\right)\end{array}\right]\left[\begin{array}{c}\mathrm{sin}\left(2\pi {f}_{i}t+{\varphi}_{i}\right)\\ \mathrm{cos}\left(2\pi {f}_{i}t+{\varphi}_{i}\right)\end{array}\right]$$
where you specify T_{s} in the Sample time parameter. Since T_{s} is constant, the righthand matrix is a constant and can be computed once at the start of the simulation. The value of A_{i}sin[2πf_{i}(t+T_{s})+ϕ_{i}] is then computed from the values of sin(2πf_{i}t+ϕ_{i}) and cos(2πf_{i}t+ϕ_{i}) by a simple matrix multiplication at each time step.
This mode offers reduced computational load, but is subject to drift over time due to cumulative quantization error. Because the method is not contingent on an absolute time value, there is no danger of discontinuity during extended operations (when an absolute time variable might overflow).
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
The Sine Wave block references absolute simulation time when configured in continuous sample mode.
HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.
HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.
This block has one default HDL architecture.
For HDL code generation, you must select the following Sine Wave block settings:
Computation method:
Table lookup
Sample mode:
Discrete
Output:
The output port cannot have data types
single
ordouble
.
This block supports code generation for complex signals.
FixedPoint Conversion
Design and simulate fixedpoint systems using FixedPoint Designer™.
If the input is fixed point, it must be a signed integer or signed fixed point with a poweroftwo slope and zero bias.
Version History
Introduced before R2006a
See Also
Blocks
 Chirp  Signal From Workspace  Signal Generator (Simulink)  Sine Wave (Simulink)  Enabled Subsystem (Simulink)
Functions
Objects
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