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Comm Filters
The Ideal Rectangular Pulse Filter block upsamples and shapes the input signal using rectangular pulses. The block replicates each input sample N times, where N is the Pulse length parameter. After replicating input samples, the block can also normalize the output signal and/or apply a linear amplitude gain.
If the Pulse delay 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.
The input can be either a scalar or a frame-based column vector. double, single, and fixed-point data types are supported.
If the input is sample-based, then the output sample time is 1/N times the input sample time. The output dimensions match the input dimensions. You must set the Input sampling mode parameter to Sample-based.
If the input is a frame-based k-by-1 matrix, then the output is a frame-based k*N-by-1 matrix. The output frame period matches the input frame period. You must set the Input sampling mode parameter to Frame-based.
The vector size (in frame-based mode), the pulse length, and the pulse delay are mutually independent. They do not need to satisfy any conditions with respect to each other.
You determine the block's normalization behavior using the Normalize output signal and Linear amplitude gain parameters.
If you clear the Normalize output signal check box, 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:
The sum of the samples in each pulse equals the original input value that the block replicated.
The energy in each pulse equals the energy of the original input value that the block replicated. That is, the sum of the squared samples in each pulse equals the square of the input value.
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.
The output is scaled by
.
If the output of this block feeds the input to the AWGN Channel block, specify the AWGN signal
power parameter to be 1/N.
The number of samples in each output pulse; that is, the number of times the block replicates each input value when creating the output signal.
The number of zeros that appear in the output at the beginning of the simulation, before the block replicates any input values.
The type of input signal: Frame-based or Sample-based.
If you select this, then the block scales the set of replicated values before applying the linear amplitude gain.
The quantity that the block considers when scaling the set of replicated values. Choices are Sum of samples and Energy per pulse. This field appears only if you select Normalize output signal.
A positive scalar used to scale the output signal.
Use this parameter to specify the rounding method to be used when 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 to Nearest.
For more information, see Rounding Modes in the Signal Processing Blockset User's Guide or Rounding Mode: Simplest in the Simulink Fixed Point documentation.
Select the overflow mode for fixed-point operations. The filter coefficients do not obey this parameter; they are always saturated.
Choose how you specify the word length and the fraction length of the filter coefficients (numerator and/or denominator). See Filter Structure Diagrams in Signal Processing Blockset Reference Guide for illustrations depicting the use of the coefficient data types in this block:
When you select 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.
When you select Specify 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 select Binary 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 select Slope 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 the Rounding mode and the Overflow mode parameters; they are always saturated and rounded to Nearest.
Use this parameter to specify how you would like to designate the product output word and fraction lengths. See Filter Structure Diagrams and Multiplication Data Types in Signal Processing Blockset Reference Guide for illustrations depicting the use of the product output data type in this block:
When you select Same as input, these characteristics match those of the input to the block.
When you select Binary point scaling, you are able to enter the word length and the fraction length of the product output, in bits.
When you select Slope 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.
Use this parameter to specify how you would like to designate the accumulator word and fraction lengths. See Filter Structure Diagrams and Multiplication Data Types for illustrations depicting the use of the accumulator data type in this block:
When you select Same as input, these characteristics match those of the input to the block.
When you select Same as product output, these characteristics match those of the product output.
When you select Binary point scaling, you are able to enter the word length and the fraction length of the accumulator, in bits.
When you select Slope 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.
Choose how you specify the output word length and fraction length:
When you select Same as input, these characteristics match those of the input to the block.
When you select Same as accumulator, these characteristics match those of the accumulator.
When you select Binary point scaling, you are able to enter the word length and the fraction length of the output, in bits.
When you select Slope 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.
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.
If Pulse length is 4 and Pulse delay is the scalar 3, then the table below shows how the block treats the beginning of a ramp (1, 2, 3,...) in several situations. (The values shown in the table do not reflect vector sizes but merely indicate numerical values.)
| Normalization Method, If Any | Linear Amplitude Gain | First Several Output Values |
|---|---|---|
| None (Normalize output signal cleared) | 1 | 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3,... |
| None (Normalize output signal cleared) | 10 | 0, 0, 0, 10, 10, 10, 10, 20, 20, 20, 20, 30, 30, 30, 30,... |
| Sum of samples | 1 | 0, 0, 0, 0.25, 0.25, 0.25, 0.25, 0.5, 0.5, 0.5, 0.5, 0.75, 0.75, 0.75, 0.75,..., where 0.25*4=1 |
| Sum of samples | 10 | 0, 0, 0, 2.5, 2.5, 2.5, 2.5, 5, 5, 5, 5, 7.5, 7.5, 7.5, 7.5,... |
| Energy per pulse | 1 | 0, 0, 0, 0.5, 0.5, 0.5, 0.5, 1.0, 1.0, 1.0, 1.0, 1.5, 1.5, 1.5, 1.5,..., where (0.5)^2*4=1^2 |
| Energy per pulse | 10 | 0, 0, 0, 5, 5, 5, 5, 10, 10, 10, 10, 15, 15, 15, 15,... |
 | Helical Interleaver | Insert Zero |  |
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