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Repeat

Resample input at higher rate by repeating values

Library

Signal Operations

dspsigops

Description

The Repeat block upsamples each channel of the Mi-by-N input to a rate L times higher than the input sample rate. To do so, the block repeats each consecutive input sample L times at the output. You specify the integer L in the Repetition count parameter.

You can use the Repeat block inside of triggered subsystems when you set the Rate options parameter to Enforce single-rate processing.

Frame-Based Processing

When you set the Input processing parameter to Columns as channels (frame based), the block upsamples each column of the input over time. In this mode, the block can perform either single-rate or multirate processing. You can use the Rate options parameter to specify how the block upsamples the input:

  • When you set the Rate options parameter to Enforce single-rate processing, the input and output of the block have the same sample rate. In this mode, the block outputs a signal with a proportionally larger frame size than the input. The block upsamples each channel independently by repeating each row of the input matrix L times at the output. For upsampling by a factor of L, the output frame size is L times larger than the input frame size (Mo = Mi*L), but the input and output frame rates are equal.

    For an example of single-rate upsampling, see Example: Single-Rate Processing.

  • When you set the Rate options parameter to Allow multirate processing, the block treats an Mi-by-N matrix input as N independent channels. The block generates the output at the faster (upsampled) rate by using a proportionally shorter frame period at the output port than at the input port. For L repetitions of the input, the output frame period is L times shorter than the input frame period (Tfo = Tfi/L). In this mode, the output always has the same frame size as the input.

    See Example: Multirate, Frame-Based Processing for an example that uses the Repeat block in this mode.

Sample-Based Processing

When you set the Input processing parameter to Elements as channels (sample based), the block treats an M-by-N matrix input as M*N independent channels, and upsamples each channel over time. The block upsamples each channel over time such that the output sample rate is L times higher than the input sample rate (Tso = Tsi/L). In this mode, the output is always the same size as the input.

Zero Latency

The Repeat block has zero-tasking latency for all single-rate operations. The block is in a single-rate mode if you set the Repetition count parameter to 1 or if you set the Input processing parameter to Columns as channels (frame based) and the Rate options parameter to Enforce single-rate processing.

The Repeat block also has zero-tasking latency for multirate operations if you run your model in Simulink® single-tasking mode.

Zero-tasking latency means that the block repeats the first input (received at t=0) for the first L output samples, the second input for the next L output samples, and so on.

Nonzero Latency

The Repeat block has tasking latency for multirate, multitasking operation:

  • In multirate, sample-based processing mode, the initial condition for each channel is repeated for the first L output samples. The channel's first input appears as output sample L+1. The Initial conditions parameter can be an Mi-by-N matrix containing one value for each channel, or a scalar to be applied to all signal channels.

  • In multirate, frame-based processing mode, the first row of the initial condition matrix is repeated for the first L output samples, the second row of the initial condition matrix is repeated for the next L output samples, and so on. The first row of the first input matrix appears in the output as sample MiL+1. The Initial conditions parameter can be an Mi-by-N matrix, or a scalar to be repeated across all elements of the Mi-by-N matrix.

Examples

Example: Single-Rate Processing

In the ex_repeat_ref2ex_repeat_ref2 model, the Repeat block resamples a single-channel input with a frame size of 16. The block repeats input values to upsample the input by a factor of 4. Thus, the output of the block has a frame size of 64. The input and output frame rates are identical.

Example: Multirate, Frame-Based Processing

In the ex_repeat_ref1ex_repeat_ref1 model, the Repeat block resamples a single-channel input with a frame period of 1 second. The block repeats input values to upsample the input by a factor of 4. Thus, the output of the block has a frame period of 0.25 seconds. The input and output frame sizes are identical.

Dialog Box

Repetition count

The integer number of times, L, that the input value is repeated at the output. This is the factor by which the block increases the output frame size or sample rate.

Input processing

Specify how the block should process the input. You can set this parameter to one of the following options:

  • Columns as channels (frame based) — When you select this option, the block treats each column of the input as a separate channel. In this mode, the block can perform single-rate or multirate processing.

  • Elements as channels (sample based) — When you select this option, the block treats each element of the input as a separate channel. In this mode, the block always performs multirate processing.

    Note:   The option Inherit from input (this choice will be removed - see release notes) will be removed in a future release. See Frame-Based Processing in the DSP System Toolbox™ Release Notes for more information.

Rate options

Specify the method by which the block upsamples the input. You can select one of the following options:

  • Enforce single-rate processing — When you select this option, the block maintains the input sample rate by increasing the output frame size by a factor of L. To select this option, you must set the Input processing parameter to Columns as channels (frame based).

  • Allow multirate processing — When you select this option, the block resamples the signal such that the output sample rate is L times faster than the input sample rate.

Initial conditions

The value with which the block is initialized for cases of nonzero latency; a scalar or matrix. This parameter appears only when you configure the block to perform multirate processing.

HDL Code Generation

This block supports HDL code generation using HDL Coder™. HDL Coder provides additional configuration options that affect HDL implementation and synthesized logic. For more information on implementations, properties, and restrictions for HDL code generation, see Repeat.

Supported Data Types

PortSupported Data Types

Input

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed and unsigned)

  • Boolean

  • 8-, 16-, and 32-bit signed integers

  • 8-, 16-, and 32-bit unsigned integers

Output

  • Double-precision floating point

  • Single-precision floating point

  • Fixed point (signed and unsigned)

  • Boolean

  • 8-, 16-, and 32-bit signed integers

  • 8-, 16-, and 32-bit unsigned integers

See Also

FIR InterpolationDSP System Toolbox
UpsampleDSP System Toolbox

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