The Raised Cosine Transmit Filter System object™ interpolates
an input signal using a raised cosine FIR filter.

To interpolate the input signal:

Define and set up your raised cosine transmit filter
object. See Construction.

Call step to interpolate
the input signal according to the properties of comm.RaisedCosineTransmitFilter.
The behavior of step is specific to each object in
the toolbox.

Construction

H = comm.RaisedCosineTransmitFilter returns
a raised cosine transmit filter System object, H,
which interpolates an input signal using a raised cosine FIR filter.
The filter uses an efficient polyphase FIR interpolation structure
and has unit energy.

H = RaisedCosineTransmitFilter(PropertyName,PropertyValue,
...) returns a raised cosine transmit filter object, H,
with each specified property set to the specified value.

Properties

Shape

Filter shape

Specify the filter shape as one of Normal or Square
root. The default is Square root.

RolloffFactor

Rolloff factor

Specify the rolloff factor as a scalar between 0 and 1.
The default is 0.2.

FilterSpanInSymbols

Filter span in symbols

Specify the number of symbols the filter spans as an integer-valued,
positive scalar. The default is 10. Because the
ideal raised cosine filter has an infinite impulse response, the object
truncates the impulse response to the value you specify for this property.

OutputSamplesPerSymbol

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 value. The raised cosine filter has (FilterSpanInSymbols x OutputSamplesPerSymbol +
1) taps.

Gain

Linear filter gain

Specify the linear gain of the filter as a positive numeric
scalar. The default is 1. The object designs a
raised cosine filter that has unit energy, and then applies the linear
gain to obtain final tap values.

This example creates a raised cosine transmit
filter with unity passband gain.

Generate a filter with unit energy. You can obtain the
filter coefficients using the coeffs method.

h = comm.RaisedCosineTransmitFilter
b = coeffs(h);

A filter with unity passband gain has filter coefficients
such that the sum of coefficients is 1. So, set the Gain property
to the inverse of the sum of b.Numerator.

h.Gain = 1/sum(b.Numerator)

Double-check the resulting filter.

bNorm = coeffs(h);
sum(bNorm.Numerator)

Plot the filter frequency response. Note that it shows
a passband gain of 0 dB, which is unity gain.