Raised Cosine Receive Filter
The block collapses the input signal with an 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 a raised cosine.
Filter Characteristics
Specifications Raised Cosine Receive Filter the same as in the block Raised Cosine Transmit Filter, except that the length of the input response of the filter has a slightly different expression: the filter range in characters , where — the value of the parameter Input samples per symbol (not Output samples per symbol, as in the case of the block Raised Cosine Transmit Filter).
The unit normalizes the filter coefficients to the unit energy. If you specify a Linear amplitude filter gain other than 1.0, the block scales the normalized filter coefficients using the gain value you specify.
Reducing the filtered signal
To thin out the filtered signal, set the Decimation factor parameter to a value greater than 1.
If represents the value of the Decimation factor parameter, then the block saves samples, selecting them as follows:
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If the Decimation offset parameter is zero, the block selects samples of the filtered signal indexed as etc.
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If the Decimation offset parameter represents a positive integer, less than , then the block initially discards this number of samples from the filtered signal and downsamples the remaining data, as in the previous case.
To save the entire filtered signal and avoid thinning, set the Decimation factor parameter to 1. This setting is appropriate, for example, when the output signal of the filter unit forms the input signal for the time phase recovery unit, such as Symbol Synchronizer. In this case, the time phase recovery unit lowers the sampling rate.
Input signals and output signals
This block accepts input signals in the form of a column vector or a matrix.
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If you set the Decimation factor parameter to
1, then the input and output signals share the same sampling mode, calculation step, and vector length. -
If you set the Decimation factor parameter to
K, which is greater than1,Kand the input sampling mode determine the characteristics of the output signal.
Ports
Entrance
In — input signal
column vector | matrix
Input signal in the form of a column vector or matrix on , where is the number of input samples per signal channel, and — the number of signal channels.
For the input signal in the form of a matrix on the block processes the columns of the input matrix as independent channels.
Data types: Float32, Float64, Fixed
Output
Out — pass output signal:q[<br>] column vector | matrix
The output signal is in the form of a column vector or matrix on , where It is defined as a relation and the values of the Decimation factor parameter, is the number of input samples per channel, and — the number of signal channels.
The block filters each channel by time and generates an output matrix. on . The output signal has the same data type as the input signal.
Data types: Float32, Float64, Fixed
Parameters
Rolloff factor — smoothing coefficient
0.2 (default) | A real number between 0 and 1
Set the smoothing coefficient of the filter. Use a real number between 0 and `1'.
Filter span in symbols — filtering range in pass characters:q[<br>] 10 (default)
Set the number of characters that the filter covers as an even, positive integer scalar. The 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 characters that this parameter specifies.
Input samples per symbol — input samples per symbol
8 (default)
An integer greater than 1 indicates the number of samples representing one character in the input signal.
Decimation factor — pass decimation factor:q[<br>] 8 (default)
Set the thinning factor that the unit applies to the input signal. The output samples per symbol are equal to the value of the input samples per symbol divided by the decimation factor. If the thinning coefficient is equal to one, then the block applies only filtering. There is no decimation.
Decimation offset — decimation offset
0 (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 (default)
Set a positive scalar value that the block uses to scale the filter coefficients. By default, the unit normalizes the filter coefficients to provide modular energy gain. If you specify a gain other than `1', the block scales the normalized filter coefficients using the gain value you specify.