The research will create a technological first – a small, lightweight, low-cost phased-array radar that uses silicon-germanium (SiGe) chips in tandem with radio-frequency micro-electromechanical systems (RF MEMS). The system being developed could be mounted on aircraft or satellites to enable high-quality mapping of ice and snow formations.
Traditionally, research on frozen areas has required bulky radar equipment that must be operated on the surface, said John Papapolymerou, a professor in Georgia Tech's School of Electrical and Computer Engineering who is principal investigator on the project. The lightweight radar approach could allow unmanned aerial vehicles (UAVs) to gather information by flying over a large area such as Greenland, using the radar system to map ice sheets in three dimensions.
"This aerial approach would greatly facilitate environmental remote sensing of ice, allowing us to map larger areas of interest to better understand location, quantity and composition," said Papapolymerou, who is teamed with another Georgia Tech professor, John Cressler, and Ted Heath, a Georgia Tech Research Institute (GTRI) senior research scientist. "This mapping ability is very important because we need to know about ice accumulation, consistency and stability.”
Phased-array radar technology uses fixed, interconnected antenna elements to send and receive multiple radar signals almost simultaneously. This approach employs a technique called phase-shifting to electronically steer the radar-signal beam.
By contrast, a conventional radar antenna changes the direction of the signal beam mechanically; the antenna moves physically among set positions, sending and receiving signals at each position. The serial approach used by conventional radar generally offers slower and less-effective performance than the more parallel technique of phased-array radar.
The basic sub-array unit under development consists of a flat grid with eight antenna elements on a side – 64 elements in all. These sub-arrays, measuring about 8.5 by 7 inches, can be combined to create a far larger radar array capable of high-quality 3-D mapping.
The sub-arrays are constructed using polymers as the substrate, which is the board-like structure in which the electronics are embedded. Polymers have numerous advantages; robust and flexible, they are also low in cost and offer good electrical performance.
To date, the researchers have produced and successfully tested an eight-by-two-element sub-array mounted on a multi-layer substrate. This substrate consists of a layer of liquid crystal polymer (LCP), which is a robust organic polymer, and a layer of a composite material called Duroid.
The LCP/Duroid substrate houses integrated circuits made from silicon-germanium (SiGe). The SiGe chips transmit and receive the radar signals via the sub-array's multiple interconnected antenna elements.
The researchers chose silicon-germanium because it offers high-performance signal amplification that is also low in noise and in power consumption, said Cressler, who is a Ken Byers Professor in the School of Electrical and Computer Engineering. SiGe chips are also robust, low in cost and highly resistant to weather and to radiation encountered in space.
"Using silicon-germanium allows much higher levels of integration, which older radar systems don’t give you," Cressler said. "It enables you to go from a system which is much larger and more expensive, and less robust, to a chip that is only a few millimeters on a side and costs far less."
Silicon-germanium circuits also interface well with RF-MEMS systems, which are tiny micro-electromechanical devices capable of movement on a very small scale. The team is using RF-MEMS devices, embedded in the substrate, to perform two functions -- switching between the transmit and receive circuits, and activating phase-shifters that electronically guide the radar signals sent by the sub-array's 64 antenna elements.
Using MEMS devices for electro-mechanical switching results in less signal loss than integrating the transmit-receive switching function within a SiGe chip electronically, Cressler said. And while MEMS switching is a bit slower than a purely electronic approach, it offers both better signal performance and the ability to handle higher signal-output power.
The system under development uses the X band -- microwave frequencies between 8 and 12 gigahertz (GHz). This band is especially effective for scanning within ice and snow deposits and remotely mapping them in three dimensions.
GTRI's Heath and his team are developing the hardware that controls the electronic components, such as the field-programmable gate arrays used by the phase-shifters to electronically steer the signal beam. The GTRI team is also designing the power supplies required by the system.
In addition, the Georgia Tech team is using the radar range at GTRI's Cobb Country Research Facility for testing.
"GTRI is tasked with taking the silicon-germanium / MEMS transmit-receive elements and putting them into a functioning radar system," Heath said. "These back-end electronics supply the power to those chips, as well as provide the signal processing and conditioning that steer the signals, and the processing of the raw data coming back."
Papapolymerou added that this approach to phased-array technology is expected to have uses in a variety of defense and commercial applications.
This research was conducted under contract number NNX-08AN22G. Any opinions, findings and conclusions or recommendations expressed in this article are those of the researchers, and do not necessarily reflect the views of the National Aeronautics and Space Administration.
Technical Contact: John Papapolymerou (404-385-6004)(email@example.com).
John Toon | Newswise Science News
New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center
Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research