Abstract: A linear interferometer antenna for making azimuth angle measurements and elevation angle measurements of an identified target. The antenna includes six radiating elements which receive signals sent from the target, a beam forming network, and a processing unit. Four of the six radiating elements are positioned on a first plane and the remaining two radiating elements are positioned on a second plane. The second plane is parallel to and positioned at a predetermined distance from the first plane.

Abstract: An antenna array for identifying aircrafts operating in a region of interest. The antenna includes a beam forming means and an antenna means. The beam forming means receives, processes and routes a sum and difference beam pattern to the antenna means. The antenna means transmits the sum and difference beam patterns to five separate beam locations in space.

Abstract: An apparatus and method for generating a directional beam for radiating or receiving electromagnetic signals having a constant beamwidth over a predetermined frequency range has been described incorporating a circular array antenna, a Butler matrix, a plurality of phase shifters, a plurality of transmission line lengths, and a power divider. The invention overcomes the problem of constant beamwidth over a predetermined frequency range such as one and one half octaves.

Abstract: The circular phased array antenna includes a plurality of radiating elements spaced about the circumference of a mounting ring. The radiating elements are fed with r.f. currents having relative phase and amplitude distribution to form a focused beam from the antenna. The beam is steerable to a selected direction. The monitor system includes a probe element mounted near each radiating element, phase shifters and couplers for combining signals from the probes into a transmission line. The amplitude of the transmission line signal is compared with a known value of signal for a normally operating antenna for each beam direction. A failure alarm is generated whenever the difference between the compared signals exceeds tolerance.

Abstract: A large N.times.N Butler matrix is comprised of a first plurality of smaller essentially flat M.times.M Butler matrices arranged in a first stack and a second plurality of smaller, essentially flat P.times.P Butler matrices arranged in a second stack in which the planes of the matrices are orthogonal to the planes of the matrices of the first plurality. M can be equal to or differ from P.

Abstract: A circular multimode antenna array having N radiating elements, an NXN Butler matrix and N-1 phase shifters includes feed networks comprising a back fill-in network, a sum pattern power divider network, a difference pattern power divider network and a sum-difference combiner network. The various networks are used either alone or in simultaneous combination to provide sum and difference circular antenna patterns having omnidirectional side lobes.