Offset antenna having improved symmetry in the radiation pattern

Claim 1

An antenna system comprising a plurality of N sequentially confocal reflectors having N+1 separate focal points comprising at least a curved focusing offset main reflector capable of bidirectionally reflecting a beam of radiated energy between the N th and the N+1 focal points along the feed axis thereof, a first subreflector disposed along the feed axis of the main reflector comprising a conic reflecting surface capable of bidirectionally reflecting said beam of radiated energy between said main reflector and an N-1 focal point of the N+1 separate focal points; and a second subreflector disposed along the feed axis of said main reflector and first subreflector comprising a conic reflecting surface capable of bidirectionally reflecting said beam of radiated energy between said first subreflector and an N-2 focal point of the N+1 separate focal points; and a symmetrical feedhorn disposed at a first focal point of said N+1 focal points and oriented with the longitudinal axis thereof coincident with an equivalent axis of the plurality of N sequentially confocal reflectors, the equivalent axis being the axis of revolution which passes through the first focal point of an equivalent reflecting surface which is capable of producing after a single reflection the same field distribution over the reflected wavefront as that of the plurality of N sequentially confocal reflectors.