US Space Force Revs Up a “Space Fence” With Wolfspeed’s Power Amplifiers

On March 27, 2020, United States Space Force (USSF) officials announced the “initial operational capability and operational acceptance of the Space Fence radar system.” Based on S-Band (2 GHz to 4 GHz) radars, the Space Fence is a ground-based system that will enhance the USSF's ability to track objects in low-earth orbit as well as those in geosynchronous orbits. Its net-centric orientation enables it to easily integrate with the existing space surveillance network.

 

Infographics of the need for Space Fence and its scope. Image used courtesy of Lockheed Martin

 

The purpose of the Space Fence will be to track and catalog objects traveling in the increasingly congested portion of space that exists just above the earth; this might include operational satellites, defunct satellites, debris left from space collisions, and the remainders of launch vehicles. These objects, traveling at speeds of up to 15,000 mph, can destroy active satellites and even put the International Space Station at risk.

 

The USSF Nods to Wolfspeed's Amplifiers

Wolfspeed has provided Lockheed Martin the Gallium Nitride (GaN) high-power amplifiers (HPA) upon which the project depends, according to Steve Bruce, vice president of the advanced systems at Lockheed Martin Mission Systems and Training.

“GaN HPAs provide significant advantages for active phased array radar systems like Space Fence, including higher power density, greater efficiency, and significantly improved reliability over previous technologies,” he says. 

Because of the classified nature of the project, we can’t know exactly which products in Wolfspeed’s extensive portfolio will be employed. But Wolfspeed does provide a product page highlighting some of its GaN on SiC (silicon carbide) components devised for satellite communications. 

 

One of Wolfspeed's Ku-Band GaN MMIC power amplifiers, the CMPA1D1E080F. The USSF has not specified which of Wolfspeeds HPAs Space Fence employs. Image used courtesy of Wolfspeed

 

Without delving into quantum mechanics, GaN, and its sister technology SiC, can both handle higher power, higher voltages, and higher frequencies than silicon-based semiconductors. GaN semiconductors, when compared to silicon, offer higher power densities, greater efficiency, and the side benefit of better tolerance of high operating temperatures.

Wolfspeed describes the merits of GaN on both SiC and silicon substrates. The first of GaN on SiC’s advantages is that it has three times the thermal conductivity GaN on silicon. The more easily heat can be removed, the more resilient a device can be. Another advantage is fewer defects on each wafer for greater manufacturing efficiency. It's no secret then, why this technology might be an attractive option to USSF in designing the Space Fence.

 

Digital Beamforming for System Flexibility

The system architecture of Space Fence is based on digital beamforming, providing for enormous operational flexibility. This enables Space Fence to electronically construct a “microfence” around objects of high interest and focus system resources specifically on that object.

 

A microfence constructed around a space object of high interest. Screenshot used courtesy of Lockheed Martin

 

The initial site location will be at the Kwajalein Atoll in the South Pacific. Each location will feature closely-based but separate receive and transmit antennas. Transmit and receive line replaceable units (LRU) can be swapped out even as the location continues functioning. 

 

The Space Fence site on the Kwajalein Atoll. Image used courtesy of Lockheed Martin

 

Everything about the system stresses minimal human power requirements, economy, and low-maintenance operation.  With an eye on the future, the USSF says the system is fully scalable.

 

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If you are involved in radar technology, how does GaN on silicon and GaN on silicon carbide stack up in your experiences? Share your thoughts in the comments below.