The miniature antenna prototype is integrated on the Husky unmanned ground vehicle through software-defined radio and other robotic sensors. The system transmits video between Husky and the second node.

New miniature low-frequency antennas with increased bandwidth will enable small mobile robots to establish strong network connections in complex environments.

In a collaborative effort between the Army Research Laboratory of the U.S. Army Combat Capability Development Command and the University of Michigan, researchers have developed a novel design method to improve the limitations of conventional antennas, which often operate at low frequencies. Run to maintain performance.

Plasma matching is a key aspect of antenna design. It ensures that the radio transmits power through the antenna with minimal reflections, while transmitting satellites, and that when the antenna is in the receiving mode, it can effectively interface with the radio on all frequencies within the business bandwidth. .

"Conventional impedance matching techniques that use passive components (such as resistors, inductors, and capacitors) have a basic limit called the Chu-Wheeler limit, which defines the maximum achievable bandwidth efficiency product boundary for a given antenna size," He said. Army researcher Dr. Fikadu Dagefu. "Generally speaking, low-frequency antennas are physically large, or their miniaturized antennas have very limited bandwidth and efficiency, resulting in higher power requirements."

With these challenges in mind, researchers have developed a novel method that can increase bandwidth and efficiency without increasing the size or changing the antenna topology.

Dr. Jihun Choi, a postdoctoral researcher in the Army, said: "The proposed impedance matching method applies modular active circuits to highly miniaturized, efficient, and lightweight antennas, thereby overcoming the aforementioned Chu-Wheeler performance limit." "This kind of miniature, active Matched antennas can integrate energy-efficient low-frequency radio systems on compact mobile agents (such as unmanned ground and aircraft)."

Researchers say this approach can create new opportunities for Army networking.

US Army researchers have developed an active matching technology to equip ground-based robotic vehicles with powerful miniature antennas.

The ability to integrate a low-frequency radio system (or SWAP) with small, light weight, and low power opens the door to use this underutilized and underexplored frequency band as part of the heterogeneous autonomous network paradigm. In this paradigm, agents equipped with supplementary communication methods must adapt their methods to the challenges of the environment in which that particular mission is located. Specifically, lower frequencies are suitable for reliable communication in complex propagation environments and terrain due to their improved penetration and reduced multipath effects.

Dagoff said: "We integrated the developed antenna on a small unmanned ground vehicle, and demonstrated reliable, real-time digital video streaming between UGVs, a compact low-frequency radio system that was not possible before. "By using this technology, robotic agents can coordinate and form teams to achieve unique functions, such as distributed on-demand beamforming for directional and secure battlefield networking."

Researchers say that by 2050, more than 80% of the world's population will live in densely populated urban environments, so innovative Army network functions are essential to create and maintain transitional excessive competition. The lack of fixed infrastructure and the increasing need for competitive advantage compared with close opponents have brought further challenges to the Army’s network, which is the primary modernization task for multi-domain operations.

Although previous experimental studies have shown that applying active matching to small non-resonant antennas (for example, short metal wires) can increase the bandwidth, compared with the small resonant antennas whose performance is close to Chu-Wheeler, there is no previous work that can simultaneously ensure The increase in bandwidth and radiation efficiency limits.

The Army-led active matching design approach addresses these major challenges, which stem from the trade-offs between bandwidth, efficiency, and stability. The researchers built a 15 cm prototype (2% of the working wavelength) and proved that compared with the same antenna without active matching, the bandwidth of the new design is increased by more than three times, and the transmission efficiency is improved compared to the state. 10 times. The most advanced active matching antenna of the same size.

Choi said: "In the design, a highly accurate model captures the sharp impedance changes of a highly miniaturized resonant antenna." "Based on this model, we developed an active matching circuit that can simultaneously improve bandwidth and efficiency. At the same time, ensure that the circuit is completely stable."

The team published their research results, namely "A Miniature Actively Matched Antenna for Power-Efficient and Bandwidth-Enhanced Operation at Low VHF" written by Drs. Cui Jixun, Fikadu Dagefu, Professor Brian Sadler and Kamal Sarabandi published a paper in the peer-reviewed journal "Antenna and Communication Affairs of the Institute of Electrical and Electronics Engineers".

Dagoff said: "This technology is mature for future development and the transition to Army partners." "We are optimistic about the integration of all aspects of heterogeneous network research. This technology will be further developed and will be Integrate into the future Army communications system."

References: Choi J, Dagefu FT, Sadler B M, et al. A Miniature Actively Matched Antenna for Power-Efficient and Bandwidth-Enhanced Operation at Low VHF[J]. IEEE Transactions on Antennas and Propagation, 2020.

The technical parameters of the Husky platform used in the article are as follows: