Multi-mode direction finding antenna

Claim 2

A multi-mode direction finding antenna comprising: (a) more than four elements positioned in a predetermined regular pattern, each of said elements having a longitudinal axis with the axes of all adjacent elements forming equal angles; (b) mode forming means having an input for each of said elements and two mode outputs, one mode output for a sum mode signal and one mode output for a difference mode signal; and (c) coupling means coupling each one of said elements to a different one of the inputs of said mode forming means.

Claim 3

An antenna is claimed in claim 1 wherein six elements are included each having a feed point adjacent one end and all of said elements are positioned with the feed points centrally located and the elements radiating outwardly therefrom.

Claim 4

An antenna as claimed in claim 1 wherein each element is generally wedge shaped.

Claim 5

An antenna as claimed in claim 1 having in addition a ground plane in spaced relation from the elements and parallel to a plane through all of the elements.

Claim 6

An antenna as claimed in claim 4 wherein the end of each element opposite the feed point is electrically connected to the ground plane by impedance matching means.

Claim 7

An antenna as claimed in claim 5 wherein each element and the associated impedance matching means forms a loop with the ground plane.

Claim 8

An antenna as claimed in claim 1 wherein the diameter of the antenna is substantially less than a wavelength at the operating frequency.

Claim 9

An antenna as claimed in claim 1 wherein the mode forming means includes a plurality of hybrid devices some of which are connected in a first configuration to electrically shift signals on adjacent elements by first equal electrical angles and provide a superposition of all the signals at a first mode output and some of which are connected in a second configuration to electrically shift signals on adjacent elements by second equal electrical angles, different than the first electrical angles, and provide a superposition between all of the signals at a second mode output.

Claim 10

An antenna as claimed in claim 8 wherein six monopole elements are included and the first electrical angles are each 60° and the second electrical angles are each 120°.

Claim 11

An antenna as claimed in claim 8 wherein the first and second mode outputs provide signals representative of a first circular polarization, and the mode forming means includes two more outputs for providing mode signals thereon representative of a second circular polarization, opposite the first polarization.

Claim 12

A multi-mode direction finding antenna comprising: (a) six monopole elements each having a longitudinal axis with the elements fixedly positioned so the longitudinal axes thereof radiate outwardly with approximately 60° between adjacent longitudinal axes; and (b) mode forming means having six inputs, each one connected to a different one of said antenna elements, and two mode outputs, said mode forming means including a first portion for electrically shifting signals from adjacent antenna elements sixty electrical degrees and providing a superposition of all six signals at a first one of the mode outputs and a second portion for electrically shifting signals from adjacent antenna elements one hundred and twenty electrical degrees and providing a superposition of all six signals at a second one of the mode outputs.

Claim 13

A multi-mode direction finding antenna comprising: (a) six monopole elements each having a longitudinal axis with the elements fixedly positioned so the longitudinal axes thereof radiate outwardly with approximately 60° between adjacent longitudinal axes; and (b) mode forming means having six inputs, each one connected to a different one of said antenna elements, and two mode outputs, said mode forming means including a first portion for electrically shifting signals from adjacent antenna elements sixty electrical degrees and providing a superposition of all six signals at a first one of the mode outputs and a second portion for electrically shifting signals from adjacent antenna elements one hundred and twenty electrical degrees and providing a superposition of all six signals at a second one of the mode outputs.