NGJ -- More than a Jammer
David A. Fulghum
2:15 PM on Jun 16, 2010
Networked armies are a reality among both conventional and insurgent forces, and as a result every antenna on the battlefield has become a target for silent, invasive attack and spying.
An airborne system that is expected to take advantage of that vulnerability is the U.S. Navy’s Next Generation Jammer (NGJ) program.
NGJ is being designed as a marriage of active electronically scanned array (AESA) antennas – combined in experimental arrays – that are controlled by easily updated and replaceable packages of software. The Navy has asked industry to assemble its best ideas for the NGJ and offer them as a catalog of ideas achievable in the near term.
Roughly, the program will be developed in two parts. The first task is designing a two-pod system for the Navy’s EA-18G Growler. The second part of the problem will be refining NGJ for the F-35 Joint Strike Fighter so that the stealth signature will not be altered.
The Navy would like to pick the best products from each competing team’s offering and mold them into a single system. Competitors object to revealing their intellectual properties to other companies. Teams include ITT/Boeing (AW&ST, May 24, p.57), Northrop Grumman (March 29, p.62), BAE Systems (Nov. 9, 2009, p.74) and Raytheon.
Basically, electronic surveillance identifies the exact location of antennas linked with the network to be attacked. A datastream of specialized waveforms and algorithms is fired from a specialized aircraft into the antenna of interest. Once inside, the digital package could, for example, transmit back what the enemy sensors see, take over control of sensors as systems administrator, mine computer memories for data and tap into remote appendages of the network such as mobile radars and missile launchers.
In fact, the EA/EW target set is more and more becoming the distributed pieces of any network that requires wireless communications or the extremities of the network such as sensors. So instead of attacking networks directly, tacticians go to those outlying elements and work their way back.
“Given that you have a limited number of stealthy aircraft, you’ve got to [generate support for] those that are not stealthy,” says Jim Bailey, Raytheon’s NGJ capture director. “Electronic attack (EA) and electronic warfare (EW) techniques are one way to help those aircraft. It is a way to use non-stealthy aircraft to complement stealth aircraft in a strike package.
“These new tools [associated with NGJ] should allow non-stealthy aircraft to penetrate farther into enemy air defense,” he says. “Threats include longer-range [air defense] missiles and improved radars. [So for a new jammer,] we want more power, better polarization control, open modular architecture, a cleaner spectrum, complete spectrum coverage, 360 degree field of regard and advanced modulation [to provide all those specialized waveforms that unlock enemy electronics].”
The goal of NGJ is to shrink the lethal range of advanced air defenses. The stealthy F-35 will likely fly into those threat rings, the non-stealthy Growler will stay outside.
“The Growlers, carrying NGJ, will apply jamming to shrink the threats’ observable, controllable, attackable space to allow our strike packages to execute their mission,” Bailey says. “[Air Defense] threats have gotten better over the years, so maintaining that modified escort arena is the result of EA/EW improvements. Any kind of jamming has to be well thought out to avoid making yourself vulnerable.”
Advanced SAM designs -- like the SA-20 (S-300)that Russia has considered selling to Iran and even newer anti-aircraft systems extending through the S-600 series -- have longer-range missiles, improved radars with electronic scanning, digital control, pulse compression, coherency, advanced electronic protection techniques and irregular tactics, U.S. analysts say.
For now, the Holy Grail for the Navy’s Next Generation Jammer is an active electronically scanned array that can scan 360 degrees and dish out electronic attack and conduct network intrusion while itself remaining impervious to any foe’s cyber and electronic weaponry.
To this point, the active electronically scanned array (AESA) has been associated with radars – which use pulses of energy -- and flat array antennas that each only produce a useable 120 degree field of view. And if the radar happens to be connected to a network, it may be vulnerable to interception, exploitation and manipulation by hackers of many types. Moreover, much of the ability to generate electronic trickery that AESA could bring to the battlefield will be the product of software upgrades that are still unfunded by Congress.
There are other emerging technical problems that NGJ will confront.
“You used to just transmit pulses to confuse the enemy,” Bailey says. “Now you have to pay attention to coherency so you can feed them something that looks like a real target.”
Another defense is the use of advanced electronic detection techniques.
“They are trying to figure out all the things we do to confuse and mislead them,” says Charles Orbell, the company’s senior manager for EW business development.
“They then design in features that enable their radar to operate in an EW environment. That’s why we need something new.”
“There are multiple threats we are trying to address,” Bailey says. “To counter advanced integrated air defenses, NGJ will have to generate multiple simultaneous beams and multiple techniques per beam. As a rule, we would like to use a pencil beam, but when you are at low frequency, physics rule and you get a fat beam.
“In addition, there will be a range of frequencies we’re trying to cover in a layered approach,” he says. “First we take care of the search radars in the lower frequencies. High frequency emitters [associated with missile radars] usually mean you against many of them. You try to find the worst threats and design the most optimal path through or around them. Then you deal with pop-ups and surprises as best you can.”
Because of the geographically diverse proliferation of advanced SAMs, part of the NGJ challenge is to address all the threats with fewer transmitters and aircraft than is required today.
The initial plan is to build a pod the size of a fuel tank for an EA-18G Growler electronic attack aircraft. In fact, the plan is for two pods, but company officials think that an interchangeable pod that can transmit out of one side at a time rather than specialized left and right pods may be a cheaper, more functional design.
The problem with fitting pod mounted NGJs to the Growler is that each is outboard of a large 480-gal. fuel tank and the low-band transmitter on the center-line station. Neither can be radiated with high-power radio frequency jamming signals from the NGJ pods. So, the solution so far appears to be pods that function to one side during each mission.
Each pod will likely carry two, 90-degree field-of-regard AESA arrays – one at the front and another at the back – each canted at a 45 degree angle from the centerline. The two then provide 180 degree coverage to each side. Other competitors are looking at a hexagon shaped AESA array with three flat arrays looking to each side.
A more complicated idea is how to change the pulsed energy output of an AESA radar, which requires less energy and cooling, to a continuous energy output needed to create predictable and repeatable effects on enemy electronics. The latter, of course, requires a lot more energy and cooling, which could be one of the tougher aspects of the program.
“Adapting AESA concepts from pulsed radar to CW operation is not so hard,” Bailey says. “The focus is packaging sufficient aperture [strings of small transmitter/receiver modules] to cover the required bandwidth at element power levels well above traditional radars. The challenges are generating enough power in the pod to feed the transmitter and cooling the system. This NGJ design will stress thermal constraints.”
ar99, NextGenerationJammer, Growler, F-35