Abstract: A quadrifilar helix antenna (1) comprising a first and a second set of helical antenna elements (2a–5a, 2b–5b) symmetrically arranged around a longitudinal axis extending through the axial center of the antenna (1). The antenna (1) is excited from feeding points (2c–5c) in a local ground plane at the bottom (6) of the antenna. The helical antenna elements (2a–5a) of the first set are interconnected in respective top ends of the elements at the top (7) of the antenna. The bottom ends of the first set are in galvanic contact with the respective feeding points (2c–5c). The antenna is characterized in that the top ends of helical antenna elements (2b–5b) of the second set are arranged in an open circuit and remain unconnected. The bottom ends of the helical antenna elements (2b–5b) of the second set each includes a connection (2d–5d) to the local ground plane.

Abstract: A quadrifilar helix antenna (1) comprising a first and a second set of helical antenna elements (2a-5a, 2b-5b) symmetrically arranged around a longitudinal axis extending through the axial center of the antenna (1). The antenna (1) is excited from feeding points (2c-5c) in a local ground plane at the bottom (6) of the antenna. The helical antenna elements (2a-5a) of the first set are interconnected in respective top ends of the elements at the top (7) of the antenna. The bottom ends of the first set are in galvanic contact with the respective feeding points (2c-5c). The antenna is characterized in that the top ends of helical antenna elements (2b-5b) of the second set are arranged in an open circuit and remain unconnected. The bottom ends of the helical antenna elements (2b-5b) of the second set each includes a connection (2d-5d) to the local ground plane.

Abstract: An inexpensive high gain antenna for use on terminals communicating with low earth orbit (LEO) satellites which include an elevation table mounted for arcuate movement about a transverse axis on an azimuth turntable mounted for rotational movement about a central axis. A plurality of antenna elements forming a phased array antenna are mounted on the top of the elevation table and have a scan plane which is parallel to and extends through the transverse axis of the elevation table. The antenna may be both mechanically and electrically scanned and is used to perform handoffs from one LEO satellite to another by positioning the elevation table of the antenna with its boresight in a direction intermediate the two satellites and with the scan plane of the antenna passing through both satellites. At the moment of of handoff, the antenna beam is electronically scanned from one satellite to another without any loss in data communication during the process.

Abstract: An antenna element intended for transmission and reception of orthogonal polarizations having a good polarization purity of electomagnetic radiation is described. It comprises a ground plane (2) and at least one radiation disc (1) connected to two ports (4, 5) for the supply of a desired electromagnetic radiation, preferably in the microwave range. The distance between the ground plane (2) and the radiation disc (1) is a fraction of the wavelength .lambda. of the radiation. The antenna element is in particular characterized in that the ports (4, 5) are located at an electric distance of 90.degree. from each other and that a quarterwave transformer (6) is added between the ground plane (2) and the radiation disc (1) that is shaped so that the transmission line impedance between the ports (4, 5) is reduced in order to make the ports radiationally independent of each other.