Northrop Grumman AN/APG-81 AESA Radar, the radar is designed to enable F-35 pilots to effectively engage air and ground targets at long range

Since the emergence of active electronically scanning array (AESA) radars in the 1990s, their use has become an increasingly central feature sought by the users of modern fighter aircraft. Not only is having an AESA radar a first-order requirement for most new models of fighters in production now, but this technology is also being inserted as a retrofit option to upgrade aircraft already in service.

Representatives of the U.S. and European radar producers have explained to AIN that “an AESA is a real force multiplier in two respects. One is that the pilot is able to become the manager of the battle space with the significant increases in the ability to track and manage targets. The other is that the large number of T/R [transmit/receive] modules makes the antenna a multi-functional array. The fighter is now no longer just tracking targets, but it is capable of conducting radar mapping, function as an ISR platform, and transmitting EW.”

The autonomy that an AESA provides—freeing the fighter pilot from dependence on an airborne early warning and control (AEW&C) aircraft or ground-controlled intercept—is an attractive capability to have because of the speed at which today's combat operations take place. The AESA also allows an aircraft to engage and fire on a larger number of targets, as well as hand-off targeting data to other aircraft.

Current Blue Competitions

The AESA models that are part of the latest “off-the-shelf” fighters in production are the Leonardo Raven ES-05 that is installed in the Saab JAS-39E, the Thales RBE2 Active Array on-board the current-production Dassault Rafale, the Boeing F/A-18E/F Super Hornet’s Raytheon AN/APG-79, and the Northrop Grumman (NG) AN/APG-81that equips Lockheed Martin’s F-35. These aircraft are in play in several markets—most notably in Canada, where the current government has ordered a full-up evaluation and competition to replace the nation’s current F/A-18A/B models still in service.

All of these aircraft except the F-35 are currently competing in India for what is still billed as the largest export fighter aircraft sale in more than 30 years. The sale should total more than 114 aircraft plus anticipated follow-on orders. In place of the F-35, Lockheed Martin is offering a revamped version of the F-16 Block 50 with an entirely new internal, electronic infrastructure. This version of the 1970s-design fighter is designated “Block 70” and includes NG’s AN/APG-83 AESA radar. The aircraft is roughly the same “F-16V” that Lockheed Martin is proposing to begin building once the production completes its move from Fort Worth, Texas, to Greenville, South Carolina.

Developed more than a decade ago, the APG-83 was originally known as the Scalable Agile Beam Radar (SABR) and was intended as part of the upgrade package for older F-16 models. Singapore, South Korea, and the Republic of China are the first three nations that are slated to have this radar set installed to replace different models of the older, mechanically steered NG AN/APG-68 radar set.

Specialists at other radar design houses question how effective the APG-83 can be since the set depends on using the airflow that cools the other avionics in the F-16 and then using an internal liquid-cooling module and heat exchanger that is on-board the radar set itself.

“This has the advantage of not having to plumb a liquid-cooling system into the aircraft, as Lockheed Martin did with the F-16E/F Block 60 for the UAE,” said a U.S. airborne radar firm’s representative. “But the question is whether or not that cooling solution allows you to run the radar’s T/R modules at their maximum capacity because of the heat that they generate. Plus there are other questions about whether the modules could be software limited in order to be in compliance with U.S. government policy” on the export of sensitive technology.

GAN Advantage

AESA radars have been in use for more than 20 years and hence the technology that is the basis for them is evolving. Most of the AESA models in production now are based on Gallium Arsenide (GaAs)-based T/R modules. However, the emerging standard now for these models of radars is the use of Gallium Nitride (GaN) technology. GaN is more efficient than the roughly 40 to 43 percent signal generation/power consumed rating of GaAs radar modules, and it also generates less heat and extends the range of the radar.

Thus far, only the ED-05 radar of the Gripen E is built with GaN-based T/R modules. Representatives from Saab pointed out to AIN that the Indian request for proposals (rfp) calls out specifically that “the aircraft they procure must incorporate GaN technology in the radar, so if the IAF and MoD follow the rfp process, the Gripen is the only fighter today that meets that requirement."

What remains to be seen is how resource-intensive or costly it would be to retrofit GaN modules into the previous-generation AESAs already in service. Most of the specialists that AIN has consulted agree that GaN is the way forward, and eventually, all of the manufacturers will have to incorporate some kind of technology-insertion regime into their production.

The Other Side

Both Russian and Chinese design bureaus have been working on developing AESA designs for their latest aircraft, but with mixed results. Russia’s NIIP had developed a new N036 model for the Sukhoi Su-57 fifth-generation fighter aircraft program. However, the Su-57 has been embraced neither by its domestic Russian Aerospace Forces (VKS) nor by India, the export customer that had been expected to purchase it in large numbers.

Thus far, there are only 12 firm orders by the VKS for the Su-57. The IAF team that examined the aircraft assessed the radar design as having significant technology shortcomings that would make it difficult to have in service on time. These included not just problems with T/R modules, but also software programming issues.

In the PRC, both the Nanjing Research of Electronic Technology (NRIET), also known as CETC No. 14 Research Institute and the AVIC 607 Research Institute, the Leihua Electronic Technology Research Institute (LETRI) have been working on AESA concepts. The Chinese design teams are looking at both smaller, AESA designs for the joint Chengdu Aerospace-PAC/Kamra JF-17 fighter, as well as radar sets for their new, stealthy-appearing aircraft: the Chengdu J-20 and Shenyang FC-31.

The sources on details for these designs do not always match, but the overall performance of the Chinese designs is an effective range that extends as far as 170 km for targets that have a three-sq-m RCS and 200 km for targets that are five square meters. The radar set for the larger J-20 is supposedly fitted with 1,000 T/R modules and has the ability to track 15 targets in track-while-scan mode while firing on up to four simultaneously.