Chelton, in partnership with Jenkins Engineering Defence Systems and BAE Systems Australia, developed and built a new sector antenna solution for the Royal Australian Navy's ship-borne, ship-to-air NATO Link16 data-link systems.
The Royal Australian Navy (RAN) required an alternative to the conventional omni-directional antenna that is currently in service. Cobham provided a solution to the RAN which met all their stated technical criteria, at a cost that was substantially lower than the current omni antenna.
The criteria for the new antennas included efficient use of the ship masthead (antenna real-estate), reduced weight to improve ship stability in high seas, significant reduction of interference caused by the ship's IFF system, and improved RF performance.
The two-input diversity capability of the ship's Link16 ViaSat Communications equipment proved to be a key enabler for this project. This made possible the use of two 180-degree sector antennas mounted lower down the mast, on the port and starboard yardarms. The combined weight of these two sector antennas was half the weight (just 20Kgs) of a conventional mast-mounted omni antenna (40Kgs). The smaller base footprint of the new Sector antenna allowed for mounting on the yardarm.
In terms of RF performance, the existing omni antenna had a peak nominal gain of 4dBi. Our new sector antennas provided a bore-sight gain of 9dBi, with a fore and aft radiation pattern cross-over point minimum gain of 5.5dBi.
The elevation patterns of the new antennas are 20 degrees, and their "fly by analysis" shows that there is no antenna up-tilt required for the anticipated flight envelopes.
IFF interference was also significantly reduced, by the use of Chelton's notch filter (1030MHz and 1090MHz).
