The National Aeronautics and Space Administration has begun a program to develop MEMS technologies that reduce the size, weight and power of its radio transceivers. Of particular concern to NASA is miniaturizing the radios for its space-constrained space walks.
NASA proposes that industrial partners begin developing reconfigurable multiband MEMS chips that can be inserted into future frequency-agile software-defined radios.
The exploration of space imposes daunting specification goals on component suppliers--demanding a combination of small size, light weight, low power, radiation immunity, vibration tolerance and extreme longevity. Luckily, those specifications read almost like a definition of microelectromechanical systems, putting MEMS in space from the earliest Shuttle launches.
"I would be surprised if there was a single Shuttle launch that did not have one of our MEMS devices on board," said Harvey Weinberg Sr., applications engineer at Analog Devices Inc. (Waltham, Mass.).
The market for any space application is naturally small, since relatively few spacecraft are launched annually, and the market for MEMS in space is no exception. On the other hand, NASA has often pioneered areas that trickle down to the military and commercial arenas, However, the reverse seems to be true for MEMS.
"In many MEMS devices, it was the commercial and military applications that came first," said John Vig, a 36-year veteran military researcher. Vig advises the Defense Advanced Research Projects Agency on its RF MEMS development program. "Darpa has a very aggressive RF MEMS program, and I'm sure that many of its developers will want to submit proposals to NASA, too," said Vig.
MEMS specifications for Earthly automotive applications also dovetail well with those of space explorations; after all, the safety of drivers and passengers in cars is not so different from the safety of astronauts in space vehicles. Likewise, automobile applications typically specify at least a 15-year life span, which matches well with the longevity requirements for deep-space probes.
"MEMS sensor development for harsh environments, such as those found in automotive, military, and telecommunications markets, has resulted in their increased adoption and expanded usage for space applications," said Jim Walker, vice president of research in semiconductor manufacturing at Gartner/Dataquest.
RF MEMS
SiTime Inc. (Sunnyvale, Calif.) already makes MEMS oscillators that operate as high as 125 MHz and is developing chips that gang multiple MEMS resonators on the same die to form the banks of RF filters needed to implement NASA's ultra-miniature software-defined radios.
"MEMS is the ideal technology for space exploration," said Aaron Partridge, chief technology officer at SiTime. "MEMS leverages the IC infrastructure to produce extremely reliable devices with very small size, very low in power consumption and insensitivity to the radiation and extreme temperatures of space."
Discera Inc. (San Jose, Calif.) also makes MEMS oscillators and is developing RF MEMS filters and other radio components. The company has had its MEMS chips tested for shock and vibration immunity by the U.S. military, via a contract with Tyco Electronics unit M/A-Com (Lowell, Mass.), which is using Discera's MOS-1 MEMS oscillator in a wireless transmitter for smart munitions. During military testing regimes, the explosives were removed from some warheads, allowing artillery shells to be retrieved after impact--and Discera's oscillators were still ticking.
"Our parts have been tested by the military for up to 50 G's of vibration, for 14,000 G's impacts, and for 25,000 G's of acceleration in a centrifuge, with 100 percent reliability--every part performed within spec with only 1.4 parts per million variation in the frequency of oscillation," said Wan-Thai Hsu, chief technology officer at Discera.
