Bandwidth capabilities of array-fed parabolic cylinders

The bandwidth of hybrid phased-array/reflector antennas, in which a large parabolic cylinder reflector is fed by a relatively small phased array, is investigated. Two types of array feeds are considered: one employs only phase-amplitude matching, the other employs amplitude and time-delay matching. In the case of phase-amplitude matching, the on-axis hybrid array/reflector designs are shown to have substantially higher bandwidth than pure phased arrays. A form of time-delay compensation is described which removes the bandwidth limitations of hybrid array/reflectors, but introduces interfering signals. This interference can be avoided by either locating the feed outside the caustic zone or by using off-axis array feeds.