Lens-fed multiple beam arrays

This type of antenna, consisting of a radiating array fed by a beam-forming lens which contains multiple output beam ports corresponding to discrete beams in space, uses lossless lenses (in the sense that each beam enjoys the full gain of the projected array aperture in its direction). Lens types used are the Rotman lens, the R-2R lens and the R-KR lens, which are computer designed and built in stripline or microstrip form on substrates having a dielectric constant selected for the desired degree of miniaturization. Arrays may be linear multibeam, two-dimensional multibeam, or circular multibeam, and have application in offensive and defensive electronic warfare, as typified by the MUSTRAC (multiple-simultaneous-target steerable telemetry tracking) system. Key characteristics of the multibeam array are multiple simultaneous beams with full array gain for each beam; fine steering between discrete beam positions to achieve continuous scanning; wide annular field-of-view; wide instantaneous frequency bandwidth; beam directions invariant with frequency; design flexibility; and no beam-steering computer required.