by MIT Lincoln Laboratory
Reliable satellite communications have become a central requirement for military operations, particularly as adversaries increase their ability to disrupt, intercept, or deny signals in contested environments. For tactical SATCOM users, the challenge is no longer simply maintaining connectivity; it is maintaining resilient links in the presence of jamming, interference, and signals-intelligence threats. This is especially important in low Earth orbit constellations, where large numbers of small satellites must operate with severe constraints on size, weight, power, and cost.
MIT Lincoln Laboratory is addressing this problem through a prototype antenna known as the Hosted Nimble Beamforming Anti-Jam Reflectarray, or HoNi BAJR. The system is intended to provide adaptive beam control for small-satellite platforms without the power and hardware burden normally associated with conventional electronically steered antenna arrays.
The need for this type of technology is growing as Proliferated Low Earth Orbit (pLEO) architectures become more common. Satellites operating in these constellations must support wide-area coverage while remaining compact and power efficient. At the same time, they must protect low-power user links from hostile or unintentional interference.
One established method for doing this is adaptive beamforming, in which an antenna modifies its radiation pattern in real time to strengthen desired signals and suppress energy arriving from unwanted directions.
Traditional adaptive arrays can perform this function, but they often require complex electronics behind each radiating element. Phased arrays, for example, typically use many active components, including phase shifters and amplifiers, distributed across the aperture. That approach provides fast beam steering, but it also increases power consumption, thermal load, cost, and system complexity. Those penalties are difficult to absorb on small spacecraft, where every watt and every cubic inch matter.
A Reflective Approach
HoNi BAJR takes a different approach. Rather than building a fully active phased array, the prototype uses a scanning reflectarray made from many individually controlled reflective elements. When RF energy illuminates the surface, each element reflects the signal with a controlled phase shift. By coordinating those phase shifts across the aperture, the antenna can form, steer, split, or shape beams as required. The reflected energy is directed toward a separate feed antenna, allowing the beamforming function to occur largely through the controlled reflective surface rather than through a dense network of active transmit/receive electronics.
This architecture offers several advantages for SWaP-constrained platforms. Because the individual reflectarray elements are relatively simple, the aperture can be scaled without redesigning a complicated beamforming network. The absence of amplifiers at every element also reduces power demand significantly. According to the Lincoln Laboratory work, the reflectarray approach can reduce power consumption by roughly 95% compared with a more conventional array implementation.
The prototype was designed with pLEO communications in mind, including operation over broad scan angles so that a satellite can maintain coverage across a large portion of the horizon. Testing at Lincoln Laboratory’s RF Systems Testing Facility demonstrated that the antenna could scan over wide angles and synthesize multipeak beams with minimal signal loss. That result is important because a reflectarray could support multiple users or coverage areas without a major penalty in link performance.
Interference Suppression
Interference suppression is another major focus of the effort. The HoNi BAJR work builds on earlier internally funded Lincoln Laboratory programs, including the Deployable Electronically Scanning Reflectarray and Phase Analog Beamforming efforts. Those programs showed that reflectarray hardware could be used to adapt antenna nulls and reduce the effect of jamming in real time.
The HoNi BAJR environment, however, presents a harder problem. In a rapidly changing signal environment, the antenna may not have enough time to identify and cancel each interference source individually. To address this, the team explored a broader suppression strategy: shaping the sidelobe structure of the antenna pattern to create regions where interference is reduced. This would allow the system to protect communications links against groups of interferers or uncertain jammer locations rather than only against precisely identified points.
Initial tests showed promise but also exposed the difficulty of controlling sidelobes with high precision. Small variations in the system can affect the final antenna pattern, making calibration an essential critical requirement. Unlike more established array types, there is limited precedent for calibrating this kind of electronically controlled reflective aperture, particularly when it must support beam steering, beam shaping, nulling, and multibeam operation.
What Comes Next
Future work will focus on improving calibration methods, refining beamforming performance, and identifying the missions where reflectarrays offer the strongest advantage. Early results suggest that the technology is especially well suited for scheduled-beam applications, power-limited spacecraft, and environments where interference is widespread but not so fast-changing that calibration and beam control cannot keep pace.
If these challenges can be solved, scanning reflectarrays could provide a practical middle ground between passive antennas and fully active phased arrays. For small satellites operating in contested pLEO constellations, that balance could be important because adaptive anti-jam performance can be achieved without the full SWaP burden of conventional array architectures.