November 2012

For Better SWaP, Choose GaN
By David Silvius, Director, Strategic Marketing
Richardson RFPD

Today’s GaN-based products are rising to the challenge of rapidly evolving demands for size, reliability, linearity, power density and energy efficiency, by providing RF system engineers with the flexibility to achieve significantly higher power and efficiency, with lower part count, board space and resultant cost. GaN technology is suited to meet today’s size, weight and power (“SWaP”) demands better than older technologies like GaAs because GaN offers: • Higher power densities leading to reduced combining losses for a given power target • Increased efficiency over frequency • Ability to maintain high performance over wide bandwidths • Higher thermal conductivity / lower thermal resistance (GaN on SiC)

And GaN is branching out to encompass more than power amplification. For example, TriQuint Semiconductor’s new GaN-based switches are capable of achieving up to five-times the power handling as GaAs. And GaN has better thermal properties than competing GaAs technologies. Thermal conductivity for SiC is roughly 4x that of GaAs. An added benefit is that GaN can support the million hour MTTF reliability benchmark at a junction temperature of 200°C or higher versus 150°C for GaAs. These thermal advantages do not solve the thermal problem at the system level; however, they bring the thermal management concern down to a reasonable design trade-off for the system engineer.

GaN switches achieve high levels of power handling in a small form factor, particularly versus insertion loss. For example, a 3 Watt GaAs switch at 6 GHz may have about 2 dB insertion loss, whereas a 40 Watt GaN switch at 6 GHz may have less than 1 dB insertion loss for the same amount of isolation. Additionally, GaN switches require very low current — measured in micro-amps (μA) as opposed to milliamps or even amps for pin switches. And because GaN essentially brings more power per mm2 to the table, small but higher power-handling components are needed to switch that level of power. TriQuint’s TGS2351-SM, for example, can switch 40W, as compared to GaAs FET-based switches which can typically switch between 3 and 10 Watts in a similar board space.

To date, the defense industry has benefitted most from advances in GaN technology, primarily due to the pulse and continuous wave GaN power devices from sup­pliers like M/A-COM Tech, Microsemi, Nitronex, TriQuint, and UMS.Applications include radar, EW and communications all of which require the output power versus size advantage that is only available through GaN. There is also plenty of GaN development in the works for commercial markets like weather and marine radar, CATV, and cellular infrastructure. For these applications, cost is a bigger driver than it is for defense applications; but as the cost of GaN is coming down, it is certainly more of an option today than it was just two years ago. Even today, GaN offers cost benefits over other technologies when viewed in terms of dollars-per-watt, as opposed to the standard dollars-per-square-millimeter comparison. As the frequency increases from S-band and X-band to Ku-band, GaN’s dollars-per-watt cost offers a markedly better value than GaAs and other existing technologies, both now and in the years ahead.

Richardson RFPD
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