  The diffraction of ultrashort pulse changes its spatial and temporal
structure that is crucial for multi-channel communication and location via such
pulses. The features of the evolution of broadband pulses discussed for two
general problems: diffraction at the edge of a flat absorbing screen and the
field near a simple caustic. The basic equations are formulated for spatial
distribution of the pulse field after the screen in the spectral and time
domain. Calculations of pulse diffraction for different wave shapes and
comparison of results are presented. We obtain an integral representation for
pulse field with arbitrary initial form near a caustic and analyze the results
for different waveforms.
