Repeat

Resample input at higher rate by repeating values

• Library:

• DSP System Toolbox / Signal 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. You specify the integer L in the Repetition count parameter.

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

Ports

Input

Port_1 — 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. That is, the frame size (number of rows) and the number of channels (columns) of the signal can change during simulation.

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

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. The size of the output depends on the Repetition count and Rate options parameters.

If you set Repetition count 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 the input is a variable-size signal, the output is also a variable-size signal.

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

Parameters

Repetition count — 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 at the output. This is the factor by which the block increases the output frame size or sample rate.

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.

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.

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.

Model Examples

Repeat Signal In Single-Rate 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

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
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 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 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.

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 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.

Best Practices

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

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).

Restrictions

Input processing set to Columns as channels (frame based) is not supported.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a

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.