Raised Cosine Transmit Filter

Apply pulse shaping by upsampling signal using raised cosine FIR filter

Library

Comm Filters

Description

The Raised Cosine Transmit Filter block upsamples and filters the input signal using a normal raised cosine FIR filter or a square root raised cosine FIR filter. The block icon shows the impulse response of the filter.

Characteristics of the Filter

TheFilter shapeparameter determines which type of filter the block uses; choices areNormalandSquare root.

The impulse response of a normal raised cosine filter with rolloff factor R and symbol period T is

$h (t) = \frac{\sin (π t / T)}{(π t / T)} \cdot \frac{\cos (π R t / T)}{(1 - 4 R^{2} t^{2} / T^{2})}$

The impulse response of a square root raised cosine filter with rolloff factor R is

$h (t) = 4 R \frac{\cos ((1 + R) π t / T) + \frac{\sin ((1 - R) π t / T)}{(4 R t / T)}}{π \sqrt{T} (1 - {(4 R t / T)}^{2})}$

The impulse response of a square root raised cosine filter convolved with itself is approximately equal to the impulse response of a normal raised cosine filter.

Because the ideal raised cosine filter has an infinite impulse response, the block truncates the impulse response to the number of symbols that theFilter span in symbolsparameter specifies. TheFilter span in symbols, N, and theOutput samples per symbol, L, determine the length of the filter's impulse response, which isL*Filter span in symbols+ 1.

TheRolloff factorparameter is the filter's rolloff factor. It must be a real number between 0 and 1. The rolloff factor determines the excess bandwidth of the filter. For example, a rolloff factor of .5 means that the bandwidth of the filter is 1.5 times the input sampling frequency.

块可实现过滤器coefficients to unit energy. If you specify aLinear amplitude filter gainother than1, then the block scales the normalized filter coefficients using the gain value you specify.

Input Signals and Output Signals

输入必须是一个离散时间信号。这种鼓风机ck accepts a column vector or matrix input signal. For information about the data types each block port supports, see theSupported Data Typetable on this page.

TheRate optionsmethod and the value of theOutput samples per symbol,L, parameter determine the characteristics of the output signal:

Single-Rate Processing

When you set theRate optionsparameter toEnforce 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_o) isLtimes larger than that of the input (M_o=M_i*L), whereLrepresents the value of theOutput samples per symbolparameter.

Multirate Processing

When you set theRate optionsparameter toAllow multirate processing, the input and output of the block are the same size. However, the sample rate of the output isLtimes faster than that of the input (i.e. the output sample time is 1/L times the input sample time). When the block is in multirate processing mode, you must also specify a value for theInput processingparameter:

When you set theInput processingparameter toElements as channels (sample based), the block treats anM-by-Lmatrix input asM*Nindependent channels, and processes each channel over time. The output sample period (T_so) isLtimes shorter than the input sample period (T_so=T_si/L), while the input and output sizes remain identical.
When you set theInput processingparameter toColumns as channels (frame based), the block treats anM_i-by-Nmatrix input asNindependent channels. The block processes each column of the input over time by keeping the frame size constant (M_i=M_o), while making the output frame period (T_fo)Ltimes shorter than the input frame period (T_fo=T_fi/L).

Exporting Filter Coefficients to theMATLABWorkspace

To examine or manipulate the coefficients of the filter that this block designs, selectExport filter coefficients to workspace. Then set theCoefficient variable nameparameter to the name of a variable that you want the block to create in the MATLAB^®workspace. Running the simulation causes the block to create the variable, overwriting any previous contents in case the variable already exists.

Parameters

Filter shape

Specify the filter shape asSquare rootorNormal.

Rolloff factor

Specify the rolloff factor of the filter. Use a real number between0and1.

Filter span in symbols

Specify the number of symbols the filter spans as an even, integer-valued positive scalar. The default is10. Because the ideal raised cosine filter has an infinite impulse response, the block truncates the impulse response to the number of symbols that this parameter specifies.

Output samples per symbol

Specify the number of output samples for each input symbol. The default is 8. This property accepts an integer-valued, positive scalar. The number of taps for the raised cosine filter equals the value of this parameter multiplied by the value of theFilter span in symbolsparameter.

Linear amplitude filter gain

Specify a positive scalar value that the block uses to scale the filter coefficients. By default, the block normalizes filter coefficients to provide unit energy gain. If you specify a gain other than1, the block scales the normalized filter coefficients using the gain value you specify.

Input processing

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

Columns as channels (frame based)——当您选择此选项,阻止对each column of the input as a separate channel.
Elements as channels (sample based)——当您选择此选项,阻止对each element of the input as a separate channel.

Rate options

Specify the method by which the block should upsample and filter the input signal. You can select one of the following 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 ofN. To select this option, you must set theInput processingparameter toColumns as channels (frame based).
Allow multirate processing— When you select this option, the block processes the signal such that the output sample rate isNtimes faster than the input sample rate.

Export filter coefficients to workspace

Select this check box to create a variable in the MATLAB workspace that contains the filter coefficients.

Visualize filter with FVTool

If you click this button, then MATLAB launches the Filter Visualization Tool,fvtool, to analyze the raised cosine filter whenever you apply any changes to the block's parameters. If you launchfvtoolfor the filter, and subsequently change parameters in the mask,fvtoolwill not update. You will need to launch a newfvtoolin order to see the new filter characteristics. Also note that if you have launchedfvtool, then it will remain open even after the model is closed.

Rounding mode

Select the rounding mode for fixed-point operations. The block uses theRounding modewhen the result of a fixed-point calculation does not map exactly to a number representable by the data type and scaling storing the result. The filter coefficients do not obey this parameter; they always round toNearest. For more information, seeRounding ModesorRounding Mode: Simplest(Fixed-Point Designer).

Saturate on integer overflow

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

Coefficients

Choose how you specify the word length and the fraction length of the filter coefficients (numerator and/or denominator). SeeFilter Structure Diagramsfor illustrations depicting the use of the coefficient data types in this block:

When you selectSame 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.
When you selectSpecify word length, you are able to enter the word length of the coefficients, in bits. 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.
When you selectBinary point scaling, you are able to enter the word length and the fraction length of the coefficients, in bits. If applicable, you are able to enter separate fraction lengths for the numerator and denominator coefficients.
When you selectSlope and bias scaling, you are able to enter the word length, in bits, and the slope of the coefficients. If applicable, you are able to enter separate slopes for the numerator and denominator coefficients. This block requires power-of-two slope and a bias of zero.
The filter coefficients do not obey theRounding modeand theSaturate on integer overflowparameters; they are always saturated and rounded toNearest.

Product output

Use this parameter to specify how you would like to designate the product output word and fraction lengths. SeeFilter Structure DiagramsandMultiplication Data Typesfor illustrations depicting the use of the product output data type in this block:

When you selectSame as input, these characteristics match those of the input to the block.
When you selectBinary point scaling, you are able to enter the word length and the fraction length of the product output, in bits.
When you selectSlope and bias scaling, you are able to enter the word length, in bits, and the slope of the product output. This block requires power-of-two slope and a bias of zero.

Accumulator

Use this parameter to specify how you would like to designate the accumulator word and fraction lengths. SeeFilter Structure DiagramsandMultiplication Data Typesfor illustrations depicting the use of the accumulator data type in this block:

When you selectSame as input, these characteristics match those of the input to the block.
When you selectSame as product output, these characteristics match those of the product output.
When you selectBinary point scaling, you are able to enter the word length and the fraction length of the accumulator, in bits.
When you selectSlope and bias scaling, you are able to enter the word length, in bits, and the slope of the accumulator. This block requires power-of-two slope and a bias of zero.

Output

Choose how you specify the output word length and fraction length:

When you selectSame as input, these characteristics match those of the input to the block.
When you selectSame as accumulator, these characteristics match those of the accumulator.
When you selectBinary point scaling, you are able to enter the word length and the fraction length of the output, in bits.
When you selectSlope and bias scaling, you are able to enter the word length, in bits, and the slope of the output. This block requires power-of-two slope and a bias of zero.

Lock data type settings against changes by the fixed-point tools

Select this parameter to prevent any fixed-point scaling you specify in this block mask from being overridden by the autoscaling tool in the Fixed-Point Tool.

Supported Data Type

Port	Supported Data Types
In	Double-precision floating point Single-precision floating point 签署了定点
Out	Double-precision floating point Single-precision floating point 签署了定点

Pair Block

Raised Cosine Receive Filter

Extended Capabilities

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

Generated code relies onmemcpyormemsetfunctions (string.h) under certain conditions.

这种鼓风机ck supports SIMD code generation using Intel AVX2 technology under these conditions:

Input processingis set toColumns as channels (frame based).
Rate optionsis set toEnforce single-rate processing.
Input signal is real-valued with real filter coefficients.
Input signal is complex-valued with real or complex filter coefficients.
Input signal has a data type ofsingleordouble.

The SIMD technology significantly improves the performance of the generated code. For details, seeGenerate SIMD Code from Simulink Blocks(Embedded Coder).

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.

这种鼓风机ck is a subsystem that contains aFIR Interpolationblock. You can setHDL Propertieson the subsystem, or you can look under the mask and setHDL Propertieson the filter block. See the "HDL Code Generation" section of theSubsystem, Atomic Subsystem, CodeReuse Subsystem(Simulink)andFIR Interpolationblock reference pages for a list of properties.

To save setting changes under the mask, you must break the library link. To break the library link, select theRaised Cosine Transmit Filterblock and execute this command.

set_param(gcb,'LinkStatus','inactive')

Version History

Introduced before R2006a

Raised Cosine Transmit Filter

Library

Description

Characteristics of the Filter

Input Signals and Output Signals

Single-Rate Processing

Multirate Processing

Exporting Filter Coefficients to theMATLABWorkspace

Parameters

Supported Data Type

Pair Block

Extended Capabilities

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

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Version History

See Also

Blocks

Objects

Functions

Raised Cosine Transmit Filter

Library

Description

Characteristics of the Filter

Input Signals and Output Signals

Single-Rate Processing

Multirate Processing

Exporting Filter Coefficients to theMATLABWorkspace

Parameters

Supported Data Type

Pair Block

Extended Capabilities

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

HDL Code GenerationGenerate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Version History

See Also

Blocks

Objects

Functions

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

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.