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  • Antennas Move out of the Radome
    Posted by David A. Fulghum 4:14 PM on Jun 17, 2010

    New antenna designs, freed from the confines of radomes, will grow dramatically in size, range and resolution. They also will drop in weight and provide advanced surveillance capabilities for even small, lightweight, unmanned aircraft.

    In addition, AESA transmitter/receiver arrays that have dominated new radar technology are moving quickly into advanced jamming, electronic attack and network invasion devices. Their unique design – with power source, receiver and transmitter stacked into a thin layer, offer advantages of 2-3 times the range and small target detection compared to conventional radars. Moreover, they can generate reliability statistics of 100 times or more that of mechanically scanned antennas.

    With AESA’s move into new missions, antennas are being regularly reinvented. In the last decade, the key building blocks have moved from brick-like transmitter/receiver modules to small tiles that were assembled in radome-sized antennas. Now they are being designed as large, thin, lightweight arrays that can be attached to the exterior of wings or bodies of aircraft and semi-rigid airships. The down side is that absorbing radical new technologies is tough on manufacturing plans.

    The pursuit of these large thin antennas is itself a step to yet another advance – the introduction of conformal arrays that can be applied to the outside of pods, wings and fuselages.  

    “The part of the technology that enables a conformal application is the extremely low weight of 2-to-5 lb. per square foot,” says Roy Azevedo, Raytheon vice president for advanced concepts and technology. “That’s 10 times less weight that current systems and it’s less than an inch thick. We’re also trying to generate a large reduction in the cost of antennas.”

    Over time, those arrays are expected to become more rugged designs that can be applied to high performance aircraft and missiles, perhaps in as few as 2-4 years. They could even be applied to the outside of pods, freeing up room for more electronic, power production and cooling inside.

    “The idea is minimal impact to the aerodynamics of the platform it is on,” Azevedo says. “We have a modular design so you can scale the antenna to any mission such as the detection of improvised explosive devices, high-resolution radar mapping, or walking people.”

    Development of the lightweight antenna puts a premium on flexibility to the point that emitters, usually called radiators, can be changed even on larger arrays.

    “Picture an assembly that is multiple layers and the radiator is just another layer in the design,” Azevedo says. “We use all the standard production processes that are available, and the design is flexible across a very wide band of frequencies if the customer wants something different.  Software can make further shifts in capability from the backend of the system.”

    Roughly, the front of the system includes the antenna, radiator, power amplifiers and the ability to do some of the signal processing while the heavy computational load is done in the processor in the separate backend.

    “Flexible software can run the antenna in different ways to produce different capabilities,” Azevedo says. “That could be running different radar modes, or it could involve sensor data fusion.

    More broadly, motivation from the Air Force’s intelligence, surveillance and reconnaissance office to put an array on an airship may see a large-scale operational application in 3-5 years. The Army also has expressed interest in the program. Aerostats with flexible skins produce another problem. The solution is to put an array inside the balloon’s envelope so that it is not affected by the flexing.

    “As the radar power aperture size gets smaller, there is performance drop,” Azevedo says. “UAVs may never have a radar that gives them great capability, but if you can cut the weight of radar by 10, you could missionize vehicles with a 3-5 ft. wingspan.

    Tags: ar99, AESA

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