Improving Military Communications with Digital Phased-Arrays at Millimeter Wave

Estimated reading time: 3 minutes

There is increasing interest in making broader use of the millimeter wave frequency band for communications on small mobile platforms where narrow antenna beams from small radiating apertures provide enhanced communication security. Today’s millimeter wave systems, however, are not user friendly and are designed to be platform specific, lacking interoperability and are thus reserved for only the most complex platforms. To expand the use of millimeter wave phased-arrays and make them broadly applicable across DoD systems, many technical challenges must be addressed, including wideband frequency coverage, precision beam pointing, user discover and mesh networking. The use of multi-beam phased arrays as well as advances in digital radio and millimeter wave technology have propelled technology to the current state, and now there is a paradigm shift on the horizon as millimeter wave phased-arrays are poised to change communication and networked mobile platforms.

Phased-arrays operating at millimeter wave–or very high frequencies–are already an active area of research by the emerging 5G cellular market. Commercial applications are primarily solving the “last mile” problem, where consumers are demanding more bandwidth for high-throughput applications over relatively short ranges at predetermined frequencies and with minimal obstacles to user discovery. DoD platforms on the other hand create far more complex communications environments. Often separated by tens or even hundreds of nautical miles, today’s military platforms are moving in three dimensions with unknown orientations. This environment is creating unique beamforming challenges that can’t easily be solved by applying current communications approaches.

“Imagine two aircraft both traveling at high speed and moving relative to one another,” said DARPA program manager Timothy Hancock. “They have to find each other in space to communicate with directional antenna beams, creating a very difficult challenge that can’t be solved with the phased-array solutions emerging in the commercial marketplace.”

To address these challenges, DARPA is launching the Millimeter-Wave Digital Arrays (MIDAS) program. Announced today, the program aims to develop element-level digital phased-array technology that will enable next generation DoD millimeter wave systems. To help solve the adaptive beamforming problem and ensure wide application of the resulting solutions, MIDAS seeks to create a common digital array tile that will enable multi-beam directional communications. Research efforts will focus on reducing the size and power of digital millimeter wave transceivers, enabling phased-array technology for mobile platforms and elevating mobile communications to the less crowded millimeter wave frequencies.

Advances in element-level digital beamforming in phased-array designs is enabling new multi-beam communications schemes—or the use of several beams receiving and transmitting in multiple directions simultaneously—to help significantly reduce node discovery time and improve network throughput. “While critical to the next generation of phased-arrays, today’s digital beamforming is limited to lower frequencies, making the resulting arrays too large for use on small mobile platforms,” said Hancock.

To reduce the size of the arrays, advances in millimeter wave technology will help push the frequency of operation to higher bands, bringing the capabilities of directional antennas to small mobile platforms. “Through MIDAS, we are seeking proposals that combine advances in millimeter wave and digital beamforming technologies to create radios that will deliver secure communications for our military,” said Hancock.

To accomplish its goals, MIDAS is focused on two key technical areas. The first is the development of the silicon chips to form the core transceiver for the array tile. The second area is focused on the development of wide-band antennas, transmit/receive (T/R) components, and the overall integration of the system that will enable the technology to be used across multiple applications, including line-of-sight communications between tactical platforms as well as current and emerging satellite communications.