Ideal Rectangular Pulse Filter

Shape input signal using ideal rectangular pulses

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Libraries:
Communications Toolbox / Comm Filters

Description

The Ideal Rectangular Pulse Filter block upsamples and shapes the input signal using rectangular pulses. After replicating input samples, the block can also normalize the output signal and apply a linear amplitude gain.

Examples

Apply Rectangular Filter to Ramp Input in Simulink

Apply ideal rectangular filtering to a ramp signal.

The cm_ideal_rect_pulse_filter model plots a ramp signal with various normalization methods applied. The model includes three Ideal Rectangular Pulse Filter blocks configured with Pulse length (number of samples) set to 4 and Pulse delay (number of samples) set to 3 to filter a ramp input signal, and an Array Plot block with default settings to display one frame of the output signals.

Run the model with Linear amplitude gain of the filters set to 1. The first three samples are zero because the filter blocks have pulse delay set to 3.

Run the model with Linear amplitude gain of filters set to 10.

Ports

Input

In — Input signal

scalar | column vector | matrix

Input signal, specified as a scalar, column vector, or K_i-by-N matrix. K_i is the number of input samples per signal channel, and N is the number of signal channels.

Data Types: double | single | fixed point

Output

Out — Output signal

column vector | matrix

Output signal, returned as a scalar, column vector, or matrix. The block filters each channel over time and generates a K_o-by-N output matrix. The output signal is the same data type as the input signal.

• K_o = K_i × L.

• N is the number of signal channels.

• K_i is the number of input samples per signal channel.

• L is the value you specify in the Pulse length (number of samples) parameter.

Data Types: double | single | fixed point

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Main

Pulse length (number of samples) — Pulse length

8 (default) | positive integer

Pulse length in samples, specified as a positive integer. The block replicates each input sample L times, where L is the pulse length that you specify in samples.

Pulse delay (number of samples) — Pulse delay

0 (default) | nonnegative integer

Pulse delay in samples, specified as a nonnegative integer. If this parameter is nonzero, then the block outputs that number of zeros at the beginning of the simulation, before starting to replicate any of the input values.

Input processing — Input processing control

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

Input processing control, specified as one of these options:

• Columns as channels (frame based) — The block treats each column of the input as a separate channel.

• Elements as channels (sample based) — The block treats each element of the input as a separate channel.

Rate options — Block processing rate

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

Block processing rate for input signal upsampling and filtering, specified as one of these options:

• Enforce single-rate processing — When you select this option, the block maintains the input sample rate and processes the signal by increasing the output frame size by a factor of N.

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

Dependencies

To use Enforce single-rate processing, you must set Input processing to Columns as channels (frame based).

Normalize output signal — Option to normalize output signal

off (default) | on

Select this parameter to scale the set of replicated values before applying the linear amplitude gain.

Normalization method — Normalization method

Sum of samples (default) | Energy per pulse

Normalization method, specified as Sum of samples or Energy per pulse. This parameter assigns the quantity that the block considers when scaling the set of replicated values. For more information, see Normalization Methods.

Dependencies

This parameter appears when you select Normalize output signal.

Linear amplitude gain — Linear gain

1 (default) | positive scalar

Linear gain, specified as a positive scalar. The block scales the output signal by the linear gain value that you specify. For more information, see Normalization Methods.

Data Types

Rounding mode — Rounding mode for fixed-point operations

Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero

Select the rounding mode for fixed-point operations. The block uses rounding mode when the result of a fixed-point calculation does not map exactly to a number representable by the data type. The filter coefficients do not obey this parameter; they always round to Nearest. For more information, see Rounding Modes or Rounding Mode: Simplest (Fixed-Point Designer).

Saturate on integer overflow — Overflow mode for fixed-point operations

off (default) | on

Select the overflow mode for fixed-point operations. The filter coefficients do not obey this parameter; they are always saturated.

Coefficients — Coefficient data type

Inherit: Same word length as input (default) | fixdt(1,16) | fixdt(1,16,0)

Specify the word length and the fraction length of the filter coefficients (numerator and denominator). For illustrations depicting the use of the coefficient data types in this block, see Filter Structure Diagrams.

When you select Inherit: Same word length as input, the word length of the filter coefficients match that of the input to the block. In this mode, the fraction length of the coefficients is automatically set to the binary-point-only scaling that provides you with the best precision possible given the value and word length of the coefficients.

The filter coefficients do not obey the Rounding mode and the Saturate on integer overflow parameters; they are always saturated and rounded to Nearest.

For information about specifying data types, see Data Type Assistant.

Product output — Product output data type

Inherit: Inherit via internal rule (default) | Inherit: Same as input | fixdt(1,16,0)

Specify the product output word and fraction lengths. For diagrams showing the use of the product output data type in this block, see the filter structure diagrams for the Discrete FIR Filter (Simulink) block and Multiplication Data Types.

• When you select Inherit: Inherit via internal rule, the block inherits the data type based on an internal rule. For more information on this rule, see Inherit via Internal Rule.

• When you select Inherit: Same as input, these characteristics match those of the input to the block.

For information about specifying data types, see Data Type Assistant.

Accumulator — Accumulator data type

Inherit via internal rule (default) | Inherit: Same as input | Inherit: Same as product output | fixdt(1,16,0)

Specify the accumulator word and fraction lengths. For diagrams showing the use of the accumulator output data type in this block, see the filter structure diagrams for the Discrete FIR Filter (Simulink) block and Multiplication Data Types.

• When you select Inherit via internal rule, the block inherits the data type based on an internal rule. For more information on this rule, see Inherit via Internal Rule.

• When you select Inherit: Same as input, these characteristics match those of the input to the block.

• When you select Inherit: Same as product output, these characteristics match those of the product output.

For information about specifying data types, see Data Type Assistant.

Output — Output data type

Inherit: Same as accumulator (default) | Inherit: Same as input | Inherit: Same as product output | fixdt(1,16,0)

Specify the output word and fraction lengths.

• When you select Inherit: Same as input, these characteristics match those of the input to the block.

• When you select Inherit: Same as accumulator, these characteristics match those of the accumulator.

• When you select Inherit: Same as product output, these characteristics match those of the product output.

For information about specifying data types, see Data Type Assistant.

Lock data type settings against changes by the fixed-point tools — Prevent fixed-point tools from overriding data types

off (default) | on

Select this parameter to prevent the fixed-point tools from overriding the data types that you specify in the block dialog box. For more information, see the Fixed-Point Tool (Fixed-Point Designer).

Block Characteristics

Data Types	double | fixed pointa | single
Multidimensional Signals	no
Variable-Size Signals	yes
a Fixed-point outputs must be signed.

More About

Data Type Assistant

The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant (Simulink).

Algorithms

Single-Rate Processing

When you set the Rate options parameter to Enforce single-rate processing, the input and output of the block have the same sample rate. To generate the output while maintaining the input sample rate, the block resamples the data in each column of the input such that the frame size of the output (M_Out) is L times larger than that of the input (M_O = M_I×L), where L is the Pulse length (number of samples) parameter value.

Multirate Processing

When you set the Rate options parameter to Allow multirate processing, the input and output of the block are the same size. However, the sample rate of the output is L times faster than that of the input and the output sample time is 1 / L times the input sample time, where L is the Pulse length (number of samples) parameter value. When the block is in multirate processing mode, you must also specify a value for the Input processing parameter.

• 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 processes each channel over time. The output sample period, T_{S_Out}, is L times shorter than the input sample period (T_{S_Out} = T_{S_In} / L), while the input and output sizes remain identical.

• When you set the Input processing parameter to Columns as channels (frame based), the block treats an M_In-by-N matrix input as N independent channels. The block processes each column of the input over time by keeping the frame size constant (M_In=M_Out), while making the output frame period, T_{F_Out}, L times shorter than the input frame period (T_{F_Out} = T_{F_In} / L).

Normalization Methods

You configure the normalization behavior of the block by using the Normalize output signal and Linear amplitude gain parameters.

• If you clear Normalize output signal, then the block multiplies the set of replicated values by the Linear amplitude gain parameter. This parameter must be a scalar.

• If you select Normalize output signal, then the Normalization method parameter appears. The block scales the set of replicated values so that one of these conditions is true:

  • When you set the Normalization method parameter to Sum of samples, the sum of the samples in each pulse equals the original input value that the block replicated. Effectively, the block uses a rectangular pulse with amplitude of (1 / L), where L is the pulse length.

  • When you set the Normalization method parameter to Energy per pulse, the sum of the squared samples in each pulse equals the square of the input value. Effectively, the block uses a rectangular pulse with amplitude of (1 / √L), where L is the pulse length.

After the block applies the scaling specified in the Normalization method parameter, it multiplies the scaled signal by the constant scalar value specified in the Linear amplitude gain parameter.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a