  The space-charge distribution of the electromagnetic field excited by point
charge moving with a constant velocity on the axis of the circular disc-loaded
waveguide was analyzed. The energy losses per structure period numerically were
calculated. With increasing charge energy main features of the waveguide modes
reach some finite values and, so way, define the limit radiation spectrum. The
saturation of the amplitudes of modes (which belongs to the lower part of the
limit spectrum) was observed. The analytical techniques and results of
calculations were discussed with the use of translation symmetry and the
problems that should be noticed were pointed out.
