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RF component vendors see uptick in military apps

Posted: 16 Jun 2003 ?? ?Print Version ?Bookmark and Share

Keywords:rf components? ieee? wlan? ldmos? tcas?

Heightened security concerns along with growing interest in WLANs and cellular basestations have prompted many components vendors at the annual IEEE Microwave Technology and Techniques Symposium to tout the suitability of their parts for military and aerospace applications.

Cree Microwave Inc., for example, found that small tweaks to its LDMOS power transistors - ordinarily used for wideband-CDMA basestation transmitters - makes them suitable for pulsed-frequency applications like L-band radar in avionics equipment. The application requires extremely high linearity, said marketing vice president John Quinn.

A new NATO avionics standard called "Mode 5" was devised in response to the 9-11 terror attacks, Quinn said. It is a variation on the Traffic Collision Avoidance Systems (TCAS) and identification friend-or-foe (IFF) systems, in which a scanned object sends back an identifier I response to a high-power pulse.

NATO Mode 5 is expected to be adopted soon as a military secure identification standard, industry sources said. "Because of security concerns, few people can tell you what Mode 5 is, except that it is a high power pulse with high linearity and dynamic range requirements," Quinn said.

Because of the dynamic range and linearity required to dissect an L-Band pulse - TCAS operates at spot frequencies from 1,030- to 1,090MHz - most designers use bipolar technology, Quinn said. However, LDMOS has been shown to offer higher gain and efficiency than bipolar transmitters at these frequencies, as well as lower packaging costs. A two-stage LDMOS power amplifier offers a 29dB gain, Quinn claimed, compared to the 24dB gain of a two-stage bipolar amplifier.

Basestation transistors are ordinarily "fragile" for high-power pulses, Quinn explained. Cree's devices are "beefed up" by extending planar source-drain "fingers" in a lateral direction - effectively putting fingers in parallel - with dual gold metal interconnects. The UGF1011 series devices are qualified up to 300W, though the company expects to show an 800W device by year-end.

M/A-Com is quietly acknowledging new business in miniaturized telemetry equipment for "smart munitions." The program has the support of several branches in the U.S. military, but the Army has been the primary driver, said Larry Burke, M/A-Com's engineering manager for telemetry products. They are embedding more monitoring and control to munitions like artillery shells, he said.

Eric Higham, business development manager for M/A-Com's RF and microwave components, said the company wants to view its military and aerospace activity as just another slice of its broad communications components business. "We're analogous to the diversified mutual fund, not the high-tech glamour stock," Higham said, although aerospace was one of the few communications markets promising any near-term growth.

"The wired cable TV market is waiting for rebirth," he said. But the automotive market seems to want antennas and millimeter-wave sensors. These would be used like car radar for warning systems in adaptive cruise control and parking aids.

Another non-military interest item for M/A-Com at the IEEE conference was a GaAs switch, a singe-pole, 6-throw device. It could be used as an antenna switch for a tri- or quad-band cell phone - one that adapts to multiple standards wherever the user goes.

But military interest remains strong, with certain caveats. Like many commercial vendors, the military is interested in small size, low cost, and rapid time-to-market. As with the telemetry transceivers which track velocity and acceleration, integration, die shrinks, and small package sizes win contracts.

While GaAs is still favored for transmitter linearity, LDMOS is used for radar power amps. SiGe is being cultivated for the integration it allows between analog and digital, between baseband and RF segments of a radio, Higham said.

M/A-Com doesn't want to "overcommit" to military and aerospace customers, but other communications market segments like infrastructure are showing "disappointing growth," Higham said. The company's strategy is to "capture [market] share through integration," he said. "But military-aerospace is starting to feel like one of the few games left in town."

- Stephan Ohr

EE Times

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