Raised Cosine Receive Filter
The block convolves the input signal with the impulse response represented as a function of the raised cosine.
blockType: SubSystem
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Description
Block Raised Cosine Receive Filter filters the input signal using a conventional FIR filter with raised cosine.
Filter characteristics
Characteristics Raised Cosine Receive Filter are the same as in the Raised Cosine Transmit Filter block, except that the filter input response length has a slightly different expression: L * filter range in symbols + 1, where L is the value of the Input samples per symbol parameter (not Output samples per symbol, as in the case of the Raised Cosine Transmit Filter block).
The block normalises the filter coefficients to unit energy. If you specify a Linear amplitude filter gain other than 1.0, the block scales the normalised filter coefficients with the gain value you specify.
Reducing the filtered signal
To have the block thin the filtered signal, set the Decimation factor parameters to a value greater than 1.
If K represents the value of the Decimation factor parameters, the block saves 1/K samples by selecting them as follows:
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If the Decimation offset parameters is zero, the block selects samples of the filtered signal indexed as , , , , etc.
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If the Decimation offset parameter is a positive integer less than M, the block initially discards that number of samples from the filtered signal and downsamples the remaining data as in the previous case.
To keep the entire filtered signal and avoid downsampling, set the Decimation factor parameters to 1. This setting is appropriate, for example, when the output signal of the filter block forms the input signal for a time phase recovery block such as Symbol Synchronizer. In this case, the time phase recovery unit performs downsampling.
Input signals and output signals
This block receives input signals in the form of a vector-column or matrix.
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If you set the Decimation factor parameters to
1, the input and output signals share the same sampling mode, calculation step and vector length. -
If you set the Decimation factor parameters to
Kwhich is greater than1,Kand the input sampling mode determine the characteristics of the output signal.
Ports
Input
In - input signal
vector-column | matrix
Input signal as a vector-column or matrix to , where is the number of input samples per signal channel and is the number of signal channels.
For an input signal as a matrix to , the unit treats the columns of the input matrix as independent channels.
Data types: Float32, Float64, Fixed
Output
Out - output signal
vector-column | matrix
Output signal as a vector-column or matrix to , where is defined as the ratio of and the value of the Decimation factor parameters, is the number of input samples per channel, and is the number of signal channels.
The block filters each channel in time and generates an output matrix to . The output signal has the same data type as the input signal.
Data types: Float32, Float64, Fixed
Parameters
Rolloff factor - smoothing factor
0.2 (by default) | A valid number between 0 and 1
Set the smoothing factor of the filter. Use a real number between 0 and 1.
Filter span in symbols - filter range in symbols
10 (By default).
Specify the number of characters that the filter spans as an even, integer positive scalar. The by default value is 10. Since 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.
Input samples per symbol - input samples per symbol
8 (By default).
An integer greater than 1 indicating the number of samples representing one symbol in the input signal.
Decimation factor - decimation factor
8 (By default).
Specify the thinning factor that the unit applies to the input signal. The output samples per character are equal to the value of the input samples per character divided by the thinning factor. If the thinning factor is one, the block applies only filtering. There is no decimation.
Decimation offset - decimation offset
0 (By default).
Set the decimation offset in the samples. Use a value between 0 and Decimation factor - 1.
Linear amplitude filter gain - linear amplitude filter gain
1.0 (By default).
Set the positive scalar value that the block uses to scale the filter coefficients. By default, the block normalises the filter coefficients to provide modular energy gain. If you specify a gain other than 1, the block scales the normalised filter coefficients using the gain value you specify.