Repeat

Resample input at higher rate by repeating values

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Libraries:
DSP System Toolbox / Signal Operations
Communications Toolbox / Sequence Operations
DSP System Toolbox HDL Support / Signal Operations

Description

The Repeat block upsamples each channel of the M_i-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. Specify the integer L in the Repetition count, L parameter or through the input port L.

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

Examples

Repeat Signal in Single-Rate Frame-Based Processing Mode

Repeat the signal in single-rate processing mode.

• Open Model

Repeat Signal in Multirate Frame-Based Processing Mode

Repeat the signal in multirate frame-based processing mode.

• Open Model

Ports

Input

in — Input signal

scalar | vector | matrix

Specify the input signal as a real or a complex-valued scalar, vector, or a matrix.

When you set Input processing to Columns as channels (frame based) and Rate options to Enforce single-rate processing, the input can be a variable-size signal. When the input is a variable-size signal, the frame size (number of rows) and the number of channels (columns) of the signal can change during simulation.

This port is unnamed until you set Repetition count source to Input port. (since R2023a)

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point
Complex Number Support: Yes

L — Repetition count

positive integer ≤ Lmax

Since R2023a

Specify the repetition count L as a positive integer less than or equal to the value you specify in the Maximum repetition count, Lmax parameter Lmax.

Dependency

To enable this port, set the Repetition count source parameter to Input port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

Output

Port_1 — Output signal

scalar | vector | matrix

The Repeat block outputs a signal that has the same data type and complexity as the input signal in. The size of the output depends on the value of the repetition count and the option you select in the Rate options parameter.

If you set Repetition count, L to L and Rate options to:

• Enforce single-rate processing — The block maintains the input sample rate by increasing the output frame size by a factor of L.

• Allow multirate processing — The block resamples the signal such that the output sample rate is L times faster than the input sample rate. The output signal has the same frame size as the input signal.

When you input the repetition count through the input port L, the Rate options parameter is automatically set to Enforce single-rate processing. In this case, the block maintains the input sample rate at the output by increasing the output frame size by a factor of L. (since R2023a)

The output is a variable-size signal when one or both of these conditions are met:

• Input is a variable-size signal.

• Repetition count is input through the port L.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point
Complex Number Support: Yes

Parameters

Repetition count source — Mode of specifying repetition count

Dialog parameter (default) | Input port

Since R2023a

Specify the repetition count through one of these options:

• Dialog parameter — The block enables the Repetition count, L parameter in the block dialog box.

• Input port — The block enables the input port L through which you specify the repetition count.

Repetition count, L — Repetition count

5 (default) | positive integer

Specify the repetition count L as a positive integer. This value is the number of times that the block repeats the input value. This is the factor by which the block increases the output frame size or sample rate.

Dependency

To enable this parameter, set Repetition count source to Dialog parameter. (since R2023a)

Maximum repetition factor, Lmax — Maximum repetition count

16 (default) | positive integer ≥ 1

Since R2023a

Specify the maximum repetition Lmax as a positive integer greater than or equal to 1. The repetition count you specify through the input port L must be less than or equal to Lmax.

Dependency

To enable this parameter, set Repetition count source to Input port.

Input processing — Method to process input signals

Columns as channels (frame based) (default) | Elements as channels (sample based)

Specify how the block should process the input by setting this parameter to one of these 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.

Dependency

To enable this parameter, set Repetition count source to Dialog parameter. (since R2023a)

When you set Repetition count source to Input port, the Input processing parameter is automatically set to Columns as channels (frame based). (since R2023a)

Rate options — Method by which block upsamples input

Enforce single-rate processing (default) | Allow multirate processing

Specify the method by which the block upsamples the input by selecting one of these 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.

Dependency

To enable this parameter, set Repetition count source to Dialog parameter. (since R2023a)

When you set Repetition count source to Input port, the Rate options parameter is automatically set to Enforce single-rate processing. (since R2023a)

Initial conditions — Initial conditions

0 (default) | scalar | matrix

Specify the value with which the block is initialized for cases of nonzero latency as a scalar or a matrix.

Dependencies

To enable this parameter, set Rate options to Allow multirate processing.

Block Characteristics

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

More About

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 (M_o = M_i*L), but the input and output frame rates are equal.

  For an example that shows how the Repeat block operates in the single-rate processing mode, see Repeat Signal in Single-Rate Frame-Based Processing Mode.

• When you set the Rate options parameter to Allow multirate processing, the block treats an M_i-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 (T_fo = T_fi/L). In this mode, the output always has the same frame size as the input.

  For an example that shows how the Repeat block operates in the multirate frame-based processing mode, see Repeat Signal in Multirate Frame-Based Processing 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 (T_so = T_si/L). In this mode, the output is always the same size as the input.

Nonzero Latency

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

• In the multirate sample-based processing mode, the block repeats the initial condition for each channel for the first L output samples. The first element of the input channel appears as output sample L+1. The Initial conditions parameter can be an M_i-by-N matrix containing one value for each channel, or a scalar value that the block applies to all signal channels.

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

Note

For more information on latency and Simulink^® tasking modes, see Excess Algorithmic Delay (Tasking Latency) and Time-Based Scheduling and Code Generation (Simulink Coder).

Zero Latency

The Repeat block has zero-tasking latency for all single-rate operations. The block is in a single-rate mode if you specify a repetition count of 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.

Extended Capabilities

C/C++ Code Generation

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

Generated code relies on the memcpy or memset function (string.h) under certain conditions.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).
SynthesisAttributes	Specifies the synthesis attributes for the blocks and block output signals in the model. The generated HDL code contains these attributes. For more information, see SynthesisAttributes (HDL Coder).

Data Type Support

The block supports these data types for HDL code generation:

Input Port	Dimension	Fixed-Point	Floating-Point	Built-in Integers	Bus	Boolean	Complex Signal
in	Scalar Vector Matrix	Yes	Single Double	Yes	Yes	Yes	Yes

When you use single or double data types as inputs to the block, you can generate synthesizable HDL code by using native floating-point technology. For more information, see Generate Target-Independent HDL Code with Native Floating-Point (HDL Coder). (since R2026a)

Block Parameter Configuration

Block Parameter	Limitations
Input processing	Input processing set to Columns as channels (frame based) is not supported.
Repetition count source	Repetition count source set to Input port is not supported.

Optimizations

The block participates in these HDL optimizations to optimize the speed, and area.

Speed Optimization

Optimization	Description
Specify Distributed Pipelining Settings (HDL Coder)	Distributed pipelining, or register retiming, is a speed optimization that moves existing delays in a design to reduce the critical path while preserving functional behavior.
Clock-Rate Pipelining (HDL Coder)	Clock-rate pipelining is an optimization framework in HDL Coder that allows other speed and area optimizations to introduce latency at the clock rate.
Delay Balancing (HDL Coder)	Using delay balancing, HDL Coder detects introduced latency along one path and then inserts matching delays on the other paths in your generated model.
Critical Path Estimation (HDL Coder)	To quickly identify the most likely critical path in your design, use Critical Path Estimation. Critical path estimation speeds up the iterative process of finding the critical path. To know blocks that are characterized in critical path estimation, see Characterized Blocks (HDL Coder).

HDL Modeling Guidelines

• When using the Repeat block to model rate transitions, see Usage of Rate Conversion Blocks (HDL Coder)

• The Repeat block uses fewer hardware resources than the Upsample block. If your algorithm does not require zero-padding upsampling, use the Repeat block.

Version History

Introduced before R2006a

R2026a: Use HDL optimizations and native floating-point

When you use single or double data types as inputs to the Repeat block, you can generate synthesizable HDL code by using native floating-point technology. To generate the HDL code with native floating-point, in the HDL Code Generation > Floating-Point pane of the Configuration Parameters dialog box, select the Use floating-point parameter. For more information on native floating-point, see Generate Target-Independent HDL Code with Native Floating-Point (HDL Coder).

You can also use various HDL optimizations, such as distributed pipelining, hierarchy flattening, or balancing, for the block to generate optimized HDL code for your DSP application.

R2023a: Tune repetition count through input port

You can now specify the repetition count through an input port when the Repeat block operates in the single-rate frame-based processing mode. When you specify the repetition count through the input port, you can change the value during simulation.

R2022b: Support for variable-size input signal

Starting in R2022b, when you set Input processing to Columns as channels (frame based) and Rate options to Enforce single-rate processing, the input can be a variable-size signal. That is, the frame size (number of rows) and the number of channels (columns) of the signal can change during simulation.

When the input is a variable-size signal, the output is also a variable-size signal.