Raised Cosine Transmit Filter
The block convolves the input signal with the impulse response represented as a function of the raised cosine.
Description
The Raised Cosine Transmit Filter unit upsamples and filters the input signal using a conventional FIR filter with raised cosine.
Filter characteristics
Since the ideal cosine filter has an infinite impulse response, the block truncates the impulse response to the number of symbols, which is set by the Filter span in symbols parameter. The filter span in symbols, N, and the number of output samples per symbol, L, determine the length of the filter impulse response, which is equal to L * filter span in symbols + 1.
The Rolloff factor parameter is the smoothing factor of the filter. It should be a real number from 0 to 1. The filter smoothing factor determines the excess bandwidth of the filter. For example, the filter smoothing factor 0.5 means that the filter bandwidth is 1.5 times the input sampling frequency.
The block normalises the filter coefficients to unit energy. If you specify a linear amplitude filter gain other than 1, the block scales the normalised filter coefficients using the gain value you specify.
Ports
Input
In - input signal
scalar | vector-column | matrix
Input signal as a scalar, column vector or matrix to , where is the number of input samples per signal channel and is the number of signal channels.
Data types: Float32, Float64, Fixed.
Output
Out - output signal
scalar | vector-column | matrix
Output signal as scalar, column vector or matrix at :
-
.
-
- number of signal channels.
-
- number of input samples per signal channel.
-
- value of the Output samples per symbol parameter.
The block filters each channel by time and generates an output matrix at . 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 length 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.
Output samples per symbol - output samples per symbol
8 (By default).
Set the number of output samples for each input symbol. The value by default is 8. This property takes an integer positive scalar value. The number of outputs for the raised cosine filter is equal to the value of this parameter multiplied by the value of Filter span in symbols.
Linear amplitude filter gain - linear filter gain factor
1.0 (by default).
Linear amplitude filter gain.