Cobham Antenna Systems, Microwave Antennas, in partnership with Jenkins Engineering Defence Systems and BAE Systems Australia, has developed and built a new antenna solution for the Royal Australian Navy’s (RAN) ship borne, ship-to-air Nato Link 16 data link systems.
The navy required an alternative to the conventional omni-directional antenna that is currently in service. Cobham Antenna Systems provided a solution to them which has met all their stated technical criteria at a cost that was substantially less than the conventional omni antenna.
There were several criteria for the new antennas, including 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 Link 16 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 20kg) of a conventional mast-mounted omni antenna (40kg). The smaller base footprint of the new Cobham antennas allowed mounting on the yardarm.
In terms of RF performance, the conventional 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 Cobham Antenna’s ‘fly by analysis’ showed no antenna up-tilt was required for the anticipated flight envelopes.
IFF interference was significantly reduced by the use of Cobham Antenna’s (1,030MHz and 1,090MHz) notch filter.