MEMS Investor Journal
MEMS has enabled a complete phased-array radar to fit on an unmanned aerial vehicle (UAV). NASA has commissioned the Georgia Institute of Technology with a $2.4 million grant to build the lightweight, low-cost and pint-sized phased array radar to map the Earth's changing ice sheets and snow formations, potentially answering vexing questions about global climate change.
"We are building the first phased-array radar that will be small enough for a UAV to carry," said John Papapolymerou, a professor in Georgia Tech’s School of Electrical and Computer Engineering who is principal investigator on the project along with professor John Cressler, and senior research scientist Ted Heath. "We are building our own RF MEMS switches, silicon germanium RF front-end chips and the antenna elements, to get the weight of the entire phased-array radar down to just a few pounds."
Phased-array radars obsolete the old-school rotating dish by using many fixed but interconnected antenna elements that can send and receive multiple radar signals and use phase-shifting to electronically steer the radar-signal beam instead of a dish. Each phased-array radar will have a total of 64 antenna elements, with the RF MEMS switches handling routing of the transmit and receive signals to the correct antenna elements.
According to the team, their RF MEMS switches will be embedded in a substrate made from liquid crystal polymer (LCP) and a composite called Duroid. The team considered adding switching functions to the SiGe chip in addition to its RF functions -- which can switch faster that mechanical switches -- but went with RF MEMS switches because of their better signal performance, their ability to handle higher output power, and less insertion-loss -- all in a convenient sized package for their ultra-small radars.
The X band -- 8-to-12 gigahertz -- microwave frequencies used by the phased-array radar will scan below snow and ice in 3D. In addition to the SiGe RF chip and MEMS switches, the design requires field-programmable gate arrays to assist in electronically steering the beam of the phased array.