  We evaluate the Lienard-Wiechert field of a rotating superluminal point
source numerically and show that this radiation field has the following
intrinsic characteristics. (i) It is sharply focused along a narrow, rigidly
rotating spiral-shaped beam that embodies the cusp of the envelope of the
emitted wave fronts. (ii) It consists of either one or three concurrent
polarization modes (depending on the relative positions of the observer and the
cusp) that constitute contributions to the field from differing retarded times.
(iii) Two of the modes are comparable in strength at both edges of the signal
and dominate over the third everywhere except in the middle of the pulse. (iv)
The position angle of the total field swings across the beam by as much as
180$^\circ$. (v) The position angles of its two dominant modes remain
approximately orthogonal throughout their excursion across the beam. Given the
fundamental nature of the Lienard-Wiechert field, the coincidence of these
characteristics with those of the radio emission that is received from pulsars
is striking.
