DSP Blockset

Example: Creating Signals with the DSP Constant Block

The DSP Constant block has the following parameters:

• Constant value
• Interpret vector parameters as 1-D
• Sample mode
• Sample time
• Frame-based output

To generate a constant matrix signal, simply enter the desired matrix in the Constant value parameter using standard MATLAB notation. Some common examples of the MATLAB matrix notation are shown below:

• [1 2 3;4 5 6]        % A 2-by-3 matrix
  [1 2 3;4 5 6]'       % The transpose, a 3-by-2 matrix
  randn(2,3)           % A 2-by-3 matrix with random elements
  [1 2 3]              % A 1-by-3 row vector
  [1 2 3]'             % The transpose, a 3-by-1 column vector
  

As with all numerical parameters, you can also enter any valid MATLAB variable or expression that evaluates to a matrix. See the MATLAB documentation for a thorough introduction to constructing and indexing matrices.

The Interpret vector parameters as 1-D and Frame-based output parameters are discussed following the example below. See the DSP Constant block's reference page for information about the Sample mode and Sample time parameters.

The model below shows five DSP Constant blocks, each generating one of the constant signals listed above. Two of the blocks have nondefault settings for the other parameters: The third block (DSP Constant2) has the Frame-based output check box selected, and the fourth block (DSP Constant3) has the Interpret vector parameters as 1-D check box selected.

In addition to the various output dimensions in the model, you can observe three different kinds of signals:

• Sample-based matrix signal -- The DSP Constant and DSP Constant1 blocks generate sample-based matrices (2-by-3 and 3-by-2, respectively) because the Frame-based output check box in those blocks is not selected. The sample-based matrices can each be considered to each have six independent channels.
• Frame-based matrix signal -- The DSP Constant2 and DSP Constant4 blocks generate frame-based matrices (2-by-3 and 3-by-1, respectively, and represented by double lines) because the Frame-based output check box in those blocks is selected. The 2-by-3 frame-based matrix is considered to have three independent channels, each containing two consecutive samples. The 3-by-1 frame-based matrix (column vector) is considered to have one independent channel, containing three consecutive samples.
• 1-D vector signal -- The DSP Constant3 block generates a length-3 1-D vector signal because the Interpret vector parameters as 1-D check box in that block is selected. This means that the output is not a matrix. However, most nonsource DSP blocks interpret a length-M 1-D vector as an M-by-1 matrix (column vector).

Note    A 1-D vector signal must always be sample-based. The Interpret vector parameters as 1-D parameter is ignored when Frame-based output is selected, or when a matrix is specified for the Constant value parameter.

See Multichannel Signals for more information about the representation of sample-based and frame-based data.

Creating Signals Using Constant Blocks

Creating Signals Using Signal Generator Blocks