Thales is “five years ahead of anybody in Europe or the U.S.” in active arrays for airborne radars, according to Jean-Nöel Stock, Thales vice-president UAVs and intelligence, and a former program director for Dassault Rafale airborne systems.
Speaking earlier this month at Thales Airborne Systems’ radar and mission systems facility in Pessac, Bordeaux, where he is also site director, Stock said one of the strengths of the Rafale program is that most of the electronics come from a single company. “The consistency we bring to the electronics means the pilot has a system that is fully integrated,” he said.
Thales’s contribution to the Rafale amounts to more than a quarter of the airplane’s dollar value, Stock said. It includes the RBE2 radar, frontal sector optronics, missile seekers (with MBDA), Damocles targeting pod and Spectra electronic warfare system. And all the data from the sensors is fuzed in a modular, data-processing unit before being displayed to the pilot or datalinked to friendly units.
Two weeks ago an RBE2 was in the final integration room at Pessac, awaiting delivery to France’s armaments agency, the DGA, for installation in the next Rafale to be produced by Dassault Aviation. It retained the passive array that will continue to be delivered through 2012. But sharing the room was an active electronically scanned array (AESA) radar already undergoing integration ahead of installation on one of the 60 tranche 4 Rafales ordered by the DGA in 2009 for delivery from 2013.
The advantage of electronic scanning is that the radar beam is directed electronically, rather than by mechanically swiveling the antenna back and forth to scan the sky. That means the beam can be switched in microseconds from one area of the sky to another, or used for ground mapping and air surveillance at the same time by flipping between the two modes.
The current RBE2’s passive antenna uses electronic lenses consisting of arrays of diodes to direct the beam horizontally and vertically. The active array eliminates the grids; instead, the front end of the antenna is populated by hundreds of transmit/receive modules, each combining a high-power transmit amplifier, low-noise, receive amplifier and beam control.
Eliminating the grids also eliminates the power lost by the signal going back and forth, improving the radar’s detection capability. “With the active array, Rafale will have a radar with twice the performance of today’s radar,” said Stock.
Such a high level of integration is made possible by the gallium-arsenide, integrated-circuit technology on which Stock bases his claim of a five-year lead in active array radar. “It was not feasible in the ’80s or ’90s and is still not feasible for many European countries,” he said. “It is not possible to integrate at this density in a combat aircraft radar without gallium arsenide. It would produce more heat and we couldn’t accommodate it.” As it is, Thales had to develop a new liquid-cooling system for the modules.
The gallium-arsenide chips, which carry out digital processing and frequency management at the same time, are produced by United Monolithic Semiconductor, a Thales/EADS joint venture based at Orsay, south of Paris, then integrated into subassemblies by Thales Micro Electronics in Brittany before being integrated into the antenna itself at Pessac. “When Rafale is exported we will find local partners for components,” Stock said. “But we will ensure we have full control of the supply chain, right down to the printed circuit boards.”
Replacing a passive with an active array is “totally plug and play” and can be achieved in two hours, he added. Future enhancements to the radar, such as a finer aperture for ground mapping in synthetic aperture radar mode and simultaneous mode operation will be achieved through new software with no change to the hardware.
In fact, Thales said, the large number of T/R modules means some of them can fail without noticeably affecting the system’s overall reliability and performance. Their reliability is such that the active front end should not require maintenance at intervals of less than 10 years.
The same gallium-arsenide technology that is transforming the RBE2 is likely to find other applications, such as a future version of the Ocean Master 4000 maritime-surveillance radar that would retain mechanical rotation but use electronic-beam tilting. Current risk assessments are also looking at applications on the Franco-British Telemos medium altitude long endurance UAV.