ptolemy.math
Class SignalProcessing.SqrtRaisedCosineSampleGenerator

java.lang.Object
  ptolemy.math.SignalProcessing.SqrtRaisedCosineSampleGenerator

All Implemented Interfaces:

DoubleUnaryOperation

Enclosing class:

SignalProcessing

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

This class generates samples of a square-root raised cosine pulse. The function computed is:

           4 x(cos((1+x)PI t/T) + T sin((1-x)PI t/T)/(4x t/T))
  h(t) =  ---------------------------------------------------
                PI sqrt(T)(1-(4 x t/T)2)
  

where x is the the excess bandwidth. This pulse convolved with itself will, in principle, be equal to a raised cosine pulse. However, because the pulse decays rather slowly for low excess bandwidth, this ideal is not closely approximated by short finite approximations of the pulse.

This implementation was 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. The implementation was then further optimized to cache computations that are independent of time.

Field Summary

private double	_eightExcessPI
private double	_excess
private double	_fourExcess
private double	_fourExcessOverPISqrtFZC
private double	_fzcOverFourExcess
private double	_fzcSqrtFZCOverEightExcessPI
private double	_oneMinus
private double	_oneMinusFZCOverFourExcess
private double	_oneOverFZC
private double	_onePlus
private double	_sampleAtZero
private double	_sixteenExcessSquared
private double	_sqrtFZC
private double	_squareFZC

Constructor Summary

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

Method Summary

double

operate(double time) Operate on the operand, returning a value of the same type.

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

_sqrtFZC

private final double _sqrtFZC

_squareFZC

private final double _squareFZC

_onePlus

private final double _onePlus

_oneMinus

private final double _oneMinus

_excess

private final double _excess

_fourExcess

private final double _fourExcess

_eightExcessPI

private final double _eightExcessPI

_sixteenExcessSquared

private final double _sixteenExcessSquared

_sampleAtZero

private final double _sampleAtZero

_fourExcessOverPISqrtFZC

private final double _fourExcessOverPISqrtFZC

_fzcSqrtFZCOverEightExcessPI

private final double _fzcSqrtFZCOverEightExcessPI

_fzcOverFourExcess

private final double _fzcOverFourExcess

_oneMinusFZCOverFourExcess

private final double _oneMinusFZCOverFourExcess

Constructor Detail

SignalProcessing.SqrtRaisedCosineSampleGenerator

public SignalProcessing.SqrtRaisedCosineSampleGenerator(double firstZeroCrossing,
                                                        double excess)

Construct a SqrtRaisedCosineSampleGenerator.

Parameters:

firstZeroCrossing - The time of the first zero crossing of the corresponding raised cosine pulse.

excess - The excess bandwidth of the corresponding raised cosine pulse (also called the rolloff factor).

Method Detail

operate

public final double operate(double time)

Description copied from interface: DoubleUnaryOperation

Operate on the operand, returning a value of the same type.

Specified by:

operate in interface DoubleUnaryOperation

Parameters:

time - The operand.

Returns:

The results of the operation.