Cree Inc of Durham, NC, USA has launched two gallium nitride (GaN) high-electron-mobility transistor (HEMT) RF devices that are said to solve a number of long-standing issues for radar systems employing traditional travelling wave tube (TWT) amplifiers. GaN-based solid-state amplifiers operating at 50V are not prone to the failure mechanisms seen with high-voltage (kV) TWT power supplies, thus providing longer lifetimes. Also, such solid-state systems provide near-instant on capability – with no warm up, longer detection ranges and improved target discrimination.
Conceived from the start to enable these system benefits, Cree's two new GaN RF transistors have been engineered to provide the highest power and efficiency housed in a small package size. It is claimed that the first device (the CGHV59350, 350W/50Ω fully matched GaN HEMT) is the highest-power C-band transistor on the market, while the second (the CGHV31500F, a 500W/50Ω GaN HEMT) is the highest-power S-band transistor fully matched to 50Ω in a single-ended package of its size. Both devices are being demonstrated at the IEEE MTT-S International Microwave Symposium (IMS 2015) in Phoenix, AZ, USA (17–21 May).
Picture: Cree's CGHV59350 and CGHV31500F GaN HEMTs.
"Cree's new C- and S-band products break power records for GaN power and efficiency performance housed in a small 50Ω package," claims Tom Dekker, director of sales & marketing, Cree RF. "This efficient power enables the economical combination of transistors to achieve multi-kilowatt power amplifiers required for defense, weather and air traffic control radar," he adds. "If we consider the figure of merit for RF power output relative to the area of a 50Ω package, Cree's 350W C-band device beats the closest commercial GaN competitor by an estimated 3.5 times. Using the same figure of merit, Cree's 500W S-band device raises the bar by 45% over other commercial S-band products."
Offering pulsed saturated power performance typically greater than 400W, the CGHV59350 is most often used in ground-based defense and Doppler weather radar systems. The 50Ω, fully matched GaN HEMT operates over a 5.2–5.9GHz bandwidth and exhibits 60% typical drain efficiency.
Delivering 700W of typical saturated RF pulsed power, the CGHV31500F is offered for air traffic control radar systems. The 50Ω, fully matched GaN HEMT operates over a 2.7–3.1GHz bandwidth and exhibits 12dB power gain.
Both devices are packaged in an industry-standard 0.7" x 0.9" ceramic/metal flange package.
