  Radio telescopes are susceptible to interference arriving through its
sidelobes. If a reflector antenna could be retrofitted with an adaptive null
steering system, it could potentially mitigate this interference. The design of
a reflectarray which can be used to reconfigure a radio telescopes radiation
pattern by driving a null to the angle of incoming interference is presented.
The reflectarray occupies only a portion of the rim of the original reflector
and lays conformal to the paraboloid within this region. The conformal
reflectarray contains unit cells with 1-bit reconfigurability stemming from two
symmetrically placed PIN diodes. It is found that the dielectric and switch
losses introduced by the reflectarray do not significantly affect the radio
telescopes efficiency since the reflectarray is placed only along the outer rim
of the reflector which is weakly illuminated. Simulation results of an L-band
reconfigurable reflectarray for an 18m prime focus fed parabola are presented.
