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.

Constructor Summary

Constructors

Constructor and Description
SqrtRaisedCosineSampleGenerator(double firstZeroCrossing, double excess) Construct a SqrtRaisedCosineSampleGenerator.

Method Summary

Modifier and Type	Method and Description
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

Constructor Detail

SqrtRaisedCosineSampleGenerator

public 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.