ptolemy.math
Class SignalProcessing.RaisedCosineSampleGenerator

java.lang.Object
  ptolemy.math.SignalProcessing.RaisedCosineSampleGenerator

All Implemented Interfaces:

DoubleUnaryOperation

Enclosing class:

SignalProcessing

public static class SignalProcessing.RaisedCosineSampleGenerator
extends java.lang.Object
implements DoubleUnaryOperation

This class generates samples of a raised cosine pulse, or if the excess is zero, a modified sinc function.

The function that is computed is:

         sin(PI t/T)   cos(excess PI t/T)
  h(t) = ----------- * -----------------
          PI t/T      1-(2 excess t/T)2
  

This is called a "raised cosine pulse" because in the frequency domain its shape is that of a raised cosine.

For some applications, you may wish to apply a window function to this impulse response, since it is rather abruptly terminated at the two \ ends.

This implementation is ported from the Ptolemy 0.x implementation by Joe Buck, Brian Evans, and Edward A. Lee. Reference: E. A. Lee and D. G. Messerschmitt, Digital Communication, Second Edition, Kluwer Academic Publishers, Boston, 1994.

Field Summary

private double	_excess
private double	_oneOverFZC

Constructor Summary

SignalProcessing.RaisedCosineSampleGenerator(double firstZeroCrossing, double excess)
Construct a RaisedCosineSampleGenerator.

Method Summary

double

operate(double time) Return a sample of the raised cosine pulse, sampled at the specified time.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_oneOverFZC

private final double _oneOverFZC

_excess

private final double _excess

Constructor Detail

SignalProcessing.RaisedCosineSampleGenerator

public SignalProcessing.RaisedCosineSampleGenerator(double firstZeroCrossing,
                                                    double excess)

Construct a RaisedCosineSampleGenerator.

Parameters:

firstZeroCrossing - The time of the first zero crossing, after time zero. This would be the symbol interval in a communications application of this pulse.

excess - The excess bandwidth (in the range 0.0 to 1.0), also called the rolloff factor.

Method Detail

operate

public final double operate(double time)

Return a sample of the raised cosine pulse, sampled at the specified time.

Specified by:

operate in interface DoubleUnaryOperation

Parameters:

time - The operand.

Returns:

The results of the operation.