Cobham Antenna Systems, 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 which was substantially lower than the 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.
A key enabler on the project was the two input diversity capability of the ship's Link16 ViaSat Communications equipment. This had the advantage of allowing the use of two 180 degree sector antennas mounted lower down the mast on 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 mounting on the yardarm.
In terms of RF performance, the existing omni antenna had a peak nominal gain of 4dBi. The new Cobham sector antennas provided a bore sight gain of 9dBi with a fore and aft radiation pattern crossover point minimum gain of 5.5dBi.
Elevation patterns of the new antennas were 20 degrees and the "fly by analysis" showed no antenna up-tilt was required for the anticipated flight envelopes.
IFF interference was also significantly reduced by the use of the Cobham Antenna System's notch filter (1030MHz and 1090MHz).