Determination and application of signal velocity for spherical wave UWB signals in FDTD

This paper proposes a numerical technique to calculate the local propagation velocity of a spherical wave UWB signal in a limited FDTD space. This method can calculate the velocity at any point to any propagation directions. Meaningful results can be obtained from the method using even a limited number of grid cells which can be accommodated by a single standard desktop machine. This velocity is a function of propagation distance and the pulse shape. As long as the significant evolution of pulse shape is present due to the numerical noise, the local signal velocity varies continually as the pulse propagates. Pulse shape, in other words the frequency range a pulse occupies, affects the propagation distance at which the pulse dispersion becomes mature. This paper makes a link between the pulse shape and observation area where the waveform evolution saturates. The obtained propagation speed can be used for the asymmetry assessment as is done with the phase velocity. An example of propagation speed used for another purpose is also presented