Future satcom needs better modems, antennas and power

Although various technologies and techniques are being used to improve military satellite capabilities, armed forces will still need to rely on commercial capabilities.

Military cutbacks and the troop pullouts from Iraq and Afghanistan aren’t slowing the race to improve the military’s satellite capabilities. Engineering teams are deploying many technologies and techniques to improve satellite capabilities, while their partners on the business side look forward to continued demand from military users.

Military planners are putting more emphasis on providing warfighters in the field access to the same data that’s available to those in central locations. That’s forcing product developers to improve throughput and reliability while reducing the size and cost of equipment.

Designers are altering all types of equipment, from modems sent into orbit to antennas carried by troops and vehicles. Design teams are pressing to develop and deploy a host of new technologies that will improve efficiency. Modems are evolving rapidly.

“We need modems with higher-order coding and modulation,” said Mark Daniels, vice president of engineering and operations at Intelsat General Corp. “Another critical technology is anti-jamming. More modem manufacturers are designing anti-access area-denial technology in.”

Modem makers are also continuing to improve throughput. Adaptive in-bound channels boost data rates and improve the ability to communicate in adverse weather conditions.

“Satellite modems are beginning to employ additional modulation - 64 amplitude phase-shift keying, for example, and coding options,” said Jim Chambers, XTAR’s engineering vice president. “Adaptive coding and modulation provides a mechanism to automatically adjust the coding and modulation to either use rain-fade margin to increase the carrier data rate during clear-sky conditions, or decrease the data rate to maintain rain margin during raining conditions.”

Several technologies help make these and other enhancements possible. Semiconductors continue to track Moore’s Law, so the capabilities of processors, memories and field- programmable gate arrays doubles every couple years. But not all electronics scale as well.

“One area of design which limits the ability to drive down the size and weight of remote modems is in power supplies,” said Karl Fuchs, vice president of technology at iDirect Government Technologies. “In many ways, power-supply components are limited by physics. For example, the dimensions of the capacitor used as part of a filter are determined by the current load. There is no Moore’s Law equivalent in the power world.”

Terminals also continue to evolve, resulting in smaller packages for constrained warfighters and vehicles. Usually, smaller antennas require more power from the satellite. But some suppliers are altering that tradeoff.

“We use a smaller antenna and do a lot more focusing and tracking,” said Tim Shroyer, chief technology officer for General Dynamics SATCOM Technologies. “It’s more expensive to build the track-and-hold technology, but you can use a narrower beam from the satellite. That’s less expensive in the long run.”

Anything done to reduce antenna size is important. Antennas remain one of the largest components in many systems, challenging the drive to comms on the move and other mobile agendas.

“New antenna technologies with improved antenna gain-to-noise-temperature (G/T) performance and side lobe characteristics are enabling the design of smaller and lighter terminals,” Fuchs said.

Other vendors are focusing on systems that communicate in many formats. Multi-mode wireless devices enable users to transmit and receive critical information through a variety of architectures.

“Users can maintain voice/data connectivity regardless of the operating environment or wireless architecture availability—if a particular Satcom system is not available, the device is able to switch to an alternative source, whether it’s a satellite, cellular, or something else, to ensure command and control is maintained,” said Mark Adams, general manager of the Specialty Applications business at ITT Exelis Electronic Systems.

Changing markets

These technology changes are occurring in a marketplace that’s also undergoing a transformation. Troop drawdowns in the Middle East and budget cutbacks are occurring as a number of military satellites are coming on line.

The Mobile User Objective System (MUOS), Advanced Extremely High Frequency (AEHF) and Wideband Global Satcom (WGS) systems are giving military users more dedicated links. However, most observers feel that military consumption of commercial satellite capabilities will continue to grow.

“Military bandwidth usage continues to go up, driven by data like UAV imagery, especially high-definition video,” Daniels said. “Even as WGS comes on line, we’re still expecting to see growth.”

Much of the military’s focus is dedicated to UHF frequencies and mobile users. These capabilities won’t significantly alter the high-bandwidth requirements of applications like video from unmanned aerial vehicles.

“MUOS will fill a significant niche for the Defense Department, but it won’t replace broadband,” Shroyer said.

Broadband satellites aren’t the only ones that will augment the military’s constellations. Iridium continues to improve its services. ITT Exelis designed the compact Iridium Short Burst Data hardware for its worldwide services, trimming size and weight by more than 50 percent.

While the DOD is using more of its own satellites, government agencies aren’t locked into the idea that they have to launch all their own communication equipment. The United States is open to having commercial suppliers handle the task of sending its systems aloft.

“We see more hosted payloads coming,” Daniels said. “We think AEHF-type payloads are a good candidate for hosted payloads.”

Additional Online Resources

General Dynamics Satcom Technologies

Intelsat Epic Satellite Platform

XTAR website
iDirect Government Technologies website