Integer Delay (DSP Blockset)

Delay an input by an integer number of sample periods.

Library

Signal Operations, in General DSP

Description

The Integer Delay block delays a discrete-time input by the number of sample intervals specified in the Delay in samples parameter. This can be a scalar value by which to equally delay all N input channels, or a vector containing one delay value for each input channel, [D(1) D(2) ... D(N)]. All the samples in channel 1 are uniformly delayed by D(1) sample intervals, all the samples in channel 2 are uniformly delayed by D(2) sample intervals, and so on. Noninteger delay values are rounded to the nearest integer.

The Frame-based inputs check box allows you to choose between sample-based and frame-based operation.

Sample-Based Operation

When the check box is not selected (default), the block assumes that the input is a 1-by-N sample vector or M-by-N sample matrix. Each of the N vector elements (or M*N matrix elements) is treated as an independent channel, and the block delays each channel as specified by the Delay in samples parameter.

The Initial conditions parameter specifies the output of the block during the initial delay. Both fixed and time-varying initial conditions can be specified in a variety of ways to suit the dimensions of the input. The initial delay for a particular channel is the time elapsed from the start of the simulation until the first input in that channel is propagated to the output.

Fixed Initial Conditions. The settings shown below specify fixed initial conditions. For a fixed initial condition, the value entered in the Initial conditions parameter is repeated at the output for each sample time of the initial delay. A fixed initial condition in sample-based mode can be specified in one of the following ways:

Scalar value to be repeated for all channels of the output at each sample time of the initial delay. For a general M-by-N input with the parameter settings below,

the block outputs a sequence of five M-by-N zero-matrices at the start of the simulation. A scalar initial condition can be used with inputs of any dimension.

Vector containing M*N elements from which to construct an M-by-N matrix to be repeated at the output for each sample time of the initial delay. M and N are the number of rows and columns, respectively, in the input matrix. The initial condition vector, ic, is reshaped columnwise to match the input matrix dimensions.

For a 2-by-3 input, and the parameters below,

the block outputs the matrix

for the first five sample times. An initial condition of length M*N can be used with inputs of any dimension, and can be specified as either a row or column vector.

Matrix of dimension M-by-N to be repeated at the output for each sample time of the initial delay, where M and N are the number of rows and columns, respectively, in the input matrix. For a 2-by-3 input, and the parameters below,

the block outputs the matrix

for the first five sample times. For cases where M=N=1 or M=1, the initial condition setting reduces to a scalar or a vector, described above.

Time-Varying Initial Conditions. The following settings specify time-varying initial conditions. For a time-varying initial condition, the values specified in the Initial conditions parameter are output in sequence during the initial delay. This allows you to specify a unique output value for each sample of the initial delay. A time-varying initial condition in sample-based mode can be specified in one of the following ways:

Vector of length D, where D is the value specified for the Delay in samples parameter. The D elements of the vector are output in sequence, one at each sample time of the initial delay. For a scalar input and the parameters shown below,

the block outputs values -1, -1, -1, 0, 1 in sequence over the first five sample times. A length-D vector initial condition can only be used with scalar inputs.

Matrix of dimension N-by-D, where N is the length of the input sample vector, and D is the value specified for the Delay in samples parameter (the maximum value if Delay in samples is a vector). The D columns of the matrix are output in sequence, one at each sample time of the initial delay. For a 1-by-3 input, and the parameters below,

the block outputs the sequence [1 -1 0], [2 -2 0], [3 -3 0], etc., for the first 5 sample times. A matrix initial condition can only be used with vector inputs.

Array of dimension M-by-N-by-D, where D is the value specified for the Delay in samples parameter (the maximum value if the Delay in samples is a vector) and M and N are the number of rows and columns, respectively, in the input matrix. The D pages of the array are output in sequence, one at each sample time of the initial delay. For a 2-by-3 input, and the parameters below,

the block outputs the matrix sequence

at the start of the simulation. An array initial condition can only be used with matrix inputs.

In sample-based mode, the Integer Delay block has direct feedthrough (inputs are available immediately at the output) when the delay on any channel is zero. As a result, Simulink may generate an error when the block is used with a zero-delay setting in feedback loops that do not contain at least one block without direct feedthrough.

Frame-Based Operation

When the Frame-based inputs check box is selected, the block assumes that the input is an M-by-N frame matrix. Each of the N frames in the matrix contains M sequential time samples from an independent channel. The illustration below shows a 6-by-4 matrix input:

The Number of channels parameter specifies the number of independent channels (columns), N, in the matrix, and the block delays each channel as specified by the Delay in samples parameter. Frame-based operation provides substantial increases in throughput rates at the expense of greater model latency.

The Initial conditions parameter specifies the output during the initial delay. Both fixed and time-varying initial conditions can be specified. The initial delay for a particular channel is the time elapsed from the start of the simulation until the first input in that channel is propagated to the output.

Fixed Initial Conditions. The settings shown below specify fixed initial conditions. The value entered in the Initial conditions parameter is repeated at the output for each sample time of the initial delay. A fixed initial condition in frame-based mode can be one of the following:

Scalar value to be repeated for all channels of the output at each sample time of the initial delay. For a general M-by-N input with the parameter settings below,

the first five samples in each of the N channels are zero. Note that if the frame size is larger than the delay, all of these zeros are all included in the first output from the block.

Vector containing N samples to be repeated at each sample time of the initial delay, where N is the Number of channels. For a two-channel ramp input ([1:100 1:100]) with a frame size of 4 and the parameter settings below,

the block outputs the following sequence of matrices at the start of the simulation.

(Note that the first five output samples of channel 1 are zero, and the first five output samples of channel 2 are -1, as specified.) If the input frame size is 1, then this operation equivalent to the sample-based operation described above.

Time-Varying Initial Condition. The following setting specifies a time-varying initial condition. For a time-varying initial condition, the values specified in the Initial conditions parameter are output in sequence during the initial delay. A time-varying initial condition in frame-based mode can be specified in the following way:

Matrix of dimension N-by-D, where N is the Number of channels in the input, and D is the value specified for the Delay in samples parameter (the maximum value if the Delay in samples is a vector). The D columns of the matrix are transposed and output in sequence (as rows), one at each sample time of the initial delay. Note that if the frame size is larger than the delay, all of the columns of the initial condition matrix are included (as rows) in the first matrix output from the block.

For a two-channel ramp input ([1:100 1:100]) with a frame size of 4 and the parameter settings below,

the block outputs the following sequence of frames at the start of the simulation.

(Note that the first five output samples of channel 1 are zero, and the first five output samples of channel 2 is the sequence -1, -2, -3, -4, -5, as specified.) If the input frame size is 1, then this operation equivalent to the sample-based operation described above.

In frame-based mode, the block has direct feedthrough when the Direct feedthrough check box is selected. In this case, Simulink may generate an error when the block is used in a feedback loop that does not contain at least one block without direct feedthrough.

If you are certain that all delays are greater than or equal to the frame size, or that there is no possibility of the block's inclusion in a feedback loop, you can safely deselect the Direct feedthrough check box. If you deselect the Direct feedthrough check box under other conditions, Simulink may generate an error.

Note
If you expect to generate code for the Integer Delay block using the Real-Time Workshop, you should ensure that inputs are contiguous in memory. See the Contiguous Copy block for more information.

Dialog Box

Delay in samples: The number of sample periods to delay the input signal.
Initial conditions: The value of the block's output during the initial delay.
Frame-based inputs: Selects frame-based operation.
Direct feedthrough: When selected, specifies that the block has direct feedthrough in frame-based mode.
Number of channels: For frame-based operation, the number of columns (frames) in the input matrix.