Researchers have created a tiny antenna for low-frequency signals. Their work cuts antenna size by nearly 10,000 times compared to old designs. This could help solve big problems in making small antennas for tough jobs like underwater searches, underground scans, and space signal guides.
The researchers describe the methods and results of this study in a paper published in PhotoniX.
Low-frequency signals range from 30 to 300 kHz. They travel far, cut through barriers, and resist interference. Normal antennas struggle here. Smaller ones lose sensitivity fast. Older tiny antennas, like magnetoelectric ones, stay stuck at centimeter sizes because their frequency ties to their length.
Silica nanoparticles levitated by lasers and charged by electron beams
The researchers used silica nanoparticles, just 143 nanometers wide, held up by lasers in a vacuum. They improved the design in key ways. First, they zapped the particles with electron beams to add charge and make them very sensitive to electric fields. Second, the particles’ frequency comes from the laser’s power, not their size. So, a 100-nanometer antenna works from 30 kHz to 180 kHz. Third, they used a method called 2FSK modulation - shifting signal patterns - to read signals clearly, with almost no errors at 0.5 kbit/s in weak fields.
This antenna tunes its frequency by tweaking the laser. It senses signals better than 10 microvolts per centimeter per square root hertz. It tracks motion in 3D, catching signals from all directions. Tests showed it can send images with few mistakes, proving it works.
Still, it’s less sensitive than big antennas by a factor of 1,000 to 10,000. Its small size and flexibility shine in harsh spots like deep seas or tight spaces. The researchers plan to improve it and reach even lower frequencies with magnetic tricks or new materials. They also hope to fit it on chips for easy use.