JED - May 2011 - (Page 42)

As GaN Pushes Ahead, the TWT Remains in a Solid State By Barry Manz When the Department of Defense d demands the development of a new technology it almost invariably gets what it wants, albeit after a considerable outlay of cash. In the domain of microwave power generation, DoD’s latest fair-haired boy is Gallium Nitride (GaN), a wide-bandgap compound semiconductor material that delivers higher power density per millimeter of gate length over a broader swath of spectrum than any other solid-state technology. In less than a decade, it has risen from an “interesting” technology with significant roadblocks in the path to commercialization to a potential challenger to gallium arsenide (GaAs) MMIC amplifiers, and with respect to EW RF power sources, the traveling-wave tube (TWT) amplifier. They key word, however, is “potential,” as the day when this challenge occurs on a large scale may be a ways off. OUT OUT WITH THE OLD…. TH OLD HE For people who remember them at all, vacuum tubes (or more respectfully, vacuum electron devices or VEDs), conjure up visions of glowing glass tubes that powered mom and dad’s radio or television sets whose CRT display weighed 50 lb. and “took too long to warm up.” Just as the CRT-based TV has largely been relegated to the annals of electronics history by the LCD and other flat-panel, high-definition displays, the DOD hopes to replace the TWT with solid-state devices to power future generations of EW systems. The government and industry have already devoted nearly $1 billion and years of work to make GaN the technology that will make this happen through DARPA-funded efforts and other programs. One of the key goals of the Next Generation Jammer (NGJ) program is to foster the development of solid-state RF power sources and “TWT lid t t d replacement.” To understand just how rapidly the star of GaN has risen, consider that only a few years ago the technology was considered too unreliable to be deployed anywhere. However, when US and allied ground forces began to encounter remotely triggered improvised explosive devices (IEDs) in Iraq, the Army determined that it needed small, broadband jammers that could be widely deployed throughout the theater – and it needed them “yesterday.” Thus was GaN pushed from the womb into the battlefield to power the jammer amplifiers for counter-IED service. In any commercial market, building amplifiers based on multiple $800 transistors would be a non-starter. But when the DOD calls, industry answers. Today, there are tens of thousands of GaN-powered jammers in service. For the TWT, which for decades

Table of Contents for the Digital Edition of JED - May 2011

JED - May 2011
The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
Washington Report
World Report
Europe’s Leading EW and SIGINT Programs
TWTs and Beyond: Putting More Power into EW
EW 101
AOC News
AOC Membership Page
Index of Advertisers
JED Quick Look

JED - May 2011