Cassegrain near-field aerial with reversible radiation propagation - uses dielectric disc and rings to provide wave phase shift at aerial aperture

摘要

The aeriel consists of a primary radiator, a primary radiator deflector, a reception reflector and a main reflector. The deflected primary radiation reaches the reception reflector and from there the main reflector through a central aperture. A dielectric disc (6) with a dielectric ring and several concentric dielectric rings can be folded round the primary radiation path behind the central aperture (5) of the main reflector (4). Alternately, a dielectric disc with one or several dielectric rings are used as an insert in the same manner. The dielectric members insertable or foldable into the primary radiation path have such relative dielectric constant and expansion (d) in the radiation longitudinal direction, as to cause a wave phase shift in the aeriel aperture of 120 to 180 deg. according to the coating and main reflector. Pref. the dielectric members are inserted or folded from behind.