Defense

Scientists bend, not break, the laws of physics.

Faced with limitations imposed by physics, laboratory researchers are generating antenna innovations by tweaking constructs to change the rules of the antenna game. Their efforts do not seek to violate long-held mathematical theorems or laws of physics. Instead, they are working to find lawful ways of working around limitations that long have inhibited the development of antennas that would suit user needs with fewer tradeoffs.

Currently, many types of antennas can be made small enough to fit in a tight area. Yet, they suffer performance drawbacks or are extremely limited in their application. Conversely, the type of antenna suitable for high-bandwidth links may prove detrimental to a use that requires low observability.

Laboratories in industry and academia are pursuing different approaches for future antenna technology breakthroughs. These efforts involve materials, architectures and network topologies. If successful, this research could lead to unobtrusive panels that replace large antennas as well as new capabilities for antenna-bearing platforms.

Howard Stuart, technical staff member at LGS Innovations, explains that the art of building smaller antennas comes up against the laws of physics. The issue is not one of miniaturization but of signal performance when antennas are built below a certain size.

“You can’t keep making antennas smaller and smaller,” Stuart points out. “There are fundamental physical limitations, and beyond that, [the antenna] is just not going to work anymore. Or, you’re going to have to give up something, such as gain.”

Beamforming could help increase capacity of cellphone networks 
to meet the demands of data-hungry smartphones and tablets.

Multi-antenna technology that could increase data capacity and maximize existing spectrum use for cellular network providers is in the early stages of development. Although widespread use of this technology will require new devices and possible network changes, the concept has shown the potential to ease mobile device congestion from smartphones and tablets. This research is underway at a time when wireless carriers worldwide are scrambling to keep up with demand for mobile data and, in some cases, are attempting to obtain additional electromagnetic spectrum.

Dubbed Argos, after a creature with 100 eyes from Greek mythology, the multiple antenna technology is being developed primarily by the Electrical and Computer Engineering Department at Rice University in Houston, Texas. Researchers at Alcatel-Lucent/Bell Labs and Yale University also are participating in the Argos program.

While Argos is being developed for electromagnetic frequencies used by smartphones and tablets, the underlying technology theoretically could be used for any device that requires an antenna, according to Clayton Shepard, a Rice graduate student who constructed the experimental Argos antenna array, which has been successfully tested. “The frequency really doesn’t matter, and eventually, we would like to make this for Wi-Fi, or any wireless application,” he says. Technology limitations of size and cost are the primary reasons why Argos is being developed for cellular network frequencies, Shepard adds.

Academic investigations are establishing the future
 of transmission technology for troops and civilians.

Improving antennas for defense or commercial purposes has as much to do with mathematics as it does with hardware. Researchers in the Wireless Networking and Communications Group at the University of Texas at Austin are exploring algorithms along with other properties that should improve communications systems on the battlefield.

A key focus of the work has honed in on multiple input, multiple output (MIMO) technology, which features many transmit and receive antennas. A large portion of that effort involves studying limited feedback—an idea that if receivers can send information back to an original transmitter, that transmitter can better configure links. This process should reduce interference and has applications for MIMO and cellular communications. Dr. Robert W. Heath Jr., director of the Wireless Networking and Communications Group (WNCG), says the research has advanced beyond single point-to-point links to examine how base stations can connect to many users and how to coordinate multiple base stations together to reduce interference.

Team members are looking into the fundamental limitations of such systems, and their results demonstrate that complete elimination of interference is not feasible only through the coordination of base stations. “That’s been something that’s surprising,” Heath states. Graduate students under his direction also are studying new analysis techniques in which they try to understand system performance and how antennas would play a role in situations with randomly located base stations. On the cellular side, experiments are underway to see how antennas can improve facets of functionality. Team members are exploring how distributing antennas throughout the cell instead of locating them all at the base station impacts performance.

U.S. Army officials

 seek to replace the

 commonly used 
device.

For decades, the U.S. Army has relied on the ubiquitous whip antenna for an array of air and ground communications, but those antennas often interfere with one another and are plainly visible to enemy soldiers in search of a target. Now, service researchers are using a wide range of technologies that could begin replacing the pervasive whip, providing more efficient, effective and reliable combat communications. Options include antennas embedded with vehicle armor, transparent antennas integrated into windshields and smart antenna technology capable of determining the optimal direction to focus transmission power.

The rule of thumb on the battlefield is that the more antennas sticking off of a vehicle, the more likely the vehicle is a high-value target with a high-ranking occupant. But this situation could change as officials at the Communications-Electronics Research, Development and Engineering Center (CERDEC), Aberdeen Proving Ground, Maryland, investigate technologies for short- and long-term replacements for whip antennas, whether for dismounted, mounted or airborne communications.

“The antenna is the intermediary between the radio and the network. You can have a state-of-the-art radio and a very substantive network, but if you don’t have the antenna, the whole thing falls apart,” says Mahbub Hoque, acting director of CERDEC’s Space and Terrestrial Communications Directorate. “We have programs in this directorate—in the antenna division—starting from basic research to develop prototypes to technology ready to transition to the program managers and program executive officers.”

U.S. Air Force researchers use 3-D printers and
 other cutting-edge concepts 
to create
 the next 
innovations.

There is no Moore’s Law for antennas because size reduction and performance improvement will always be subject to the limitations imposed by electromagnetic physics and material properties. But steady advances in computer technologies, such as electromagnetic modeling and simulation and 3-D printing, enable antenna technology researchers to push the limits of possibility on behalf of the warfighters.

Scientists and engineers at the U.S. Air Force Research Laboratory (AFRL), Antenna Technology Branch, Wright-Patterson Air Force Base, Ohio, are taking advantage of these technological advances to develop next-generation antennas. Experts say metamaterials show great promise for military antennas, but the technology is not yet at a point where it is being manufactured widely. To help overcome that challenge, Air Force researchers use a 3-D printer to prototype antenna metamaterials that potentially could advance technology beyond the more conventional microstrip antenna. Small, lightweight, low-cost microstrip antennas, which were invented about four decades ago, are used in military aircraft, missiles, rockets and satellite communications as well as in the commercial sector.

“It allows us a capability in rapid prototyping that we didn’t have before,” says David Curtis, the AFRL’s Antenna Technology Branch chief. “It’s yielding some interesting things. It’s creating new ground planes for antenna elements.”