Preventing adversaries from interfering with communications is crucial to national security. Tactical satellite communications (SATCOM) focus on securing reliable communications channels against adversaries in contested environments. A team from MIT Lincoln Laboratory is building a prototype antenna characterized by low size, weight, power, and cost (SWaP-C). In proliferated low Earth orbit (pLEO), threats such as signal jamming and signals intelligence necessitate low-SWaP antennas. Mitigating these threats involves real-time beam shaping to prevent interference with ground users' signals.
"Looking toward the future challenges of tactical SATCOM, there is a clear need for novel approaches to radio-frequency (RF) aperture designs that are scalable and low SWaP-C without sacrificing functionality," says Michael Craton, a technical staff member in Lincoln Laboratory's Tactical Satellite Communications Group.
To tackle interference and jamming, the team developed the Hosted Nimble Beamforming Anti-Jam Reflectarray (HoNi BAJR), a scanning reflectarray antenna prototype. The reflectarray's surface consists of individually controlled reflective elements that reflect energy with phase shifts to form beams that block interference. This simplicity allows easy scaling and control of the array.
Unlike phased arrays, which require amplifiers for each element, reflectarrays collect signals via a feed antenna, significantly lowering SWaP and enhancing scalability. The HoNi BAJR prototype is designed for pLEO communications, providing wide coverage for low-power users amidst jamming. Testing at the RF Systems Testing Facility demonstrated high scan angles and minimal signal loss when synthesizing multipeak beams, confirming the capability to serve multiple users without data loss.
Suppressing interference from unwanted signals is crucial for proper antenna function. The work is based on two internally funded R&D programs: Deployable Electronically Scanning Reflectarray (DESRa) and Phase Analog Beamforming (PhAB). PhAB showed real-time adaptation to nulls and jamming. However, in HoNi BAJR's dynamic environment, rapid beam adaptation may be challenging. The team innovated by creating interference suppression regions through side lobe shaping, though this faced calibration difficulties due to sensitivity.
Calibration is vital yet challenging for reflectarrays, and the team is researching calibration methods for scanning reflectarrays. Enhancements in beam shaping and forming will depend on effective calibration. Identifying optimal applications for reflectarrays is another focus area. "Designing hardware is always a challenge, but integrating technology into a functional system that meets mission needs is the hardest part," Craton notes.
Early studies indicate that reflectarrays can function well in scheduled beam scenarios and low-dynamic environments, as well as on power-constrained platforms. Future efforts will explore reflectarray applications further, improve calibration procedures, and refine beamforming capabilities.
Blogger's Review: This research highlights the significance of reflectarrays in ensuring secure low Earth orbit satellite communications, especially in interference-prone environments. With reduced power consumption and complexity, this technology has the potential to bolster future tactical communication systems, warranting attention for its ongoing development and practical implementation.