Abstract: An antenna system including: an input port configured to receive tracking mode signals, in two orthogonal polarizations, from a target; a tracking coupler, configured to receive the tracking mode signals from the input port, the tracking coupler including: a first pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a first one of the orthogonal polarizations, and a second pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a second one of the orthogonal polarizations; and a tracking combiner network configured to combine the extracted tracking signals from the pairs of opposed slot couplers to generate tracking output signals for use in controlling the antenna system to track the target.

Abstract: A circularly polarized array antenna (30) is disclosed. A single layer dielectric substrate (36) has a ground plane (32) located on its upper surface of the substrate and covering only part of the upper surface. A plurality of antenna elements (40-54) are also located on said upper surface of the substrate. Each antenna element has a slot element (60-74) formed in the ground plane and a respective loading element (80-94) located within each slot element. The antenna elements being arranged in a regular array where each respective slot element is sequentially rotated in space with respect to adjacent slot elements, and the loading elements generate a perturbation under excitation. A microstrip feed network (100) is located on the underside of the substrate to provide excitation to each slot element, and including feeds of different lengths to be electrically sequentially rotated in common with spatial rotation of the slot elements.

Abstract: An antenna system including: an input port configured to receive tracking mode signals, in two orthogonal polarisations, from a target; a tracking coupler, configured to receive the tracking mode signals from the input port, the tracking coupler including: a first pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a first one of the orthogonal polarisations, and a second pair of opposed slot couplers configured to extract tracking signals from the tracking mode signals in a second one of the orthogonal polarisations; and a tracking combiner network configured to combine the extracted tracking signals from the pairs of opposed slot couplers to generate tracking output signals for use in controlling the antenna system to track the target.

Abstract: A circularly polarised array antenna (30) is disclosed. A single layer dielectric substrate (36) has a ground plane (32) located on its upper surface of the substrate and covering only part of the upper surface. A plurality of antenna elements (40-54) are also located on said upper surface of the substrate. Each antenna element has a slot element (60-74) formed in the ground plane and a respective loading element (80-94) located within each slot element. The antenna elements being arranged in a regular array where each respective slot element is sequentially rotated in space with respect to adjacent slot elements, and the loading elements generate a perturbation under excitation. A microstrip feed network (100) is located on the underside of the sub-straw to provide excitation to each slot element, and including feeds of different lengths to be electrically sequentially rotated in common with spatial rotation of the slot elements.

Abstract: A directional planar antenna is disclosed. The antenna has an array of coaxial ring-slot radiating elements formed through a conductive layer on a dielectric substrate. A number of probes, coupled to the ring-slot elements, selectively excite a separate resonant mode on each ring-slot element. The resonant mode supported by a ring-slot element depends upon the geometry of that ring-slot element. The resonant modes combine in the far field to form a radiation pattern directional in azimuth and elevation. By adjustment of the relative phase difference or relative amplitude between the excited modes, the radiation pattern can be steered.