2 July 2014

DARPA's ELASTx program demos 94GHz fully integrated all-silicon system-on-a-chip transmitter

Researchers with the program ‘Efficient Linearized All-Silicon Transmitter ICs’ (ELASTx) of the US Defense Advanced Research Projects Agency (DARPA) have demonstrated an all-silicon system-on-a-chip (SoC) transmitter that operates at 94GHz. This marks the first time that a silicon-only SoC has achieved such a high frequency, which falls in the millimeter-wave range used for many military applications such as radar, guidance systems and communications. The DARPA performer for the all-silicon SoC is Northrop Grumman Aerospace Systems.

Picture: Photo of 94GHz all-silicon system-on-a-chip transmitter.

Many existing compact, high-data-rate millimeter-wave wireless communications systems use integrated circuits made with gallium arsenide (GaAs) or gallium nitride (GaN) that provide high power and efficiency in small packages but are costly to produce and difficult to integrate with the silicon electronics that provide most other radio functions. Silicon ICs are less expensive to manufacture in volume than those with gallium compounds but until now have not demonstrated sufficient power output and efficiency at millimeter-wave frequencies used for communications and other military applications such as radar and guidance systems.

“What normally would require multiple circuit boards, separate metal shielded assemblies and numerous I/O cables we can now miniaturize onto one silicon chip,” says DARPA program manager Dev Palmer. “This accomplishment opens the door for co-designing digital CMOS [complementary metal oxide semiconductors] and millimeter-wave capabilities as an integrated system on an all-silicon chip, which should also make possible new design architectures for future military RF systems,” he adds.

The all-silicon SoC transmitter uses a digitally assisted power amplifier that dynamically adapts amplifier performance characteristics to changing signal requirements. This capability allows for simultaneous optimization of efficiency and linearity - a key goal of all transmitters and power amplifiers designed to quickly deliver large amounts of data on the emerging, net-dependent battlefield.

“This SoC can support a range of modulation formats, so it’s possible to communicate to multiple systems using different waveforms from a single silicon chip,” Palmer says. “Its efficient silicon construction will significantly reduce SWAP [size, weight, and power] requirements for millimeter-wave applications, including compact satellite communications ground terminals for frontline troops,” he believes. “These new capabilities will provide connectivity to more service members faster and at lower cost.”

Tags:  CMOS Northrop Grumman

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