a brand new form of pocket-sized antenna, evolved at the branch of power’s SLAC countrywide Accelerator Laboratory, may want to allow mobile verbal exchange in conditions wherein traditional radios don’t paintings, together with beneath water, through the floor and over very lengthy distances through air.
The device emits very low frequency (VLF) radiation with wavelengths of tens to hundreds of miles. those waves tour lengthy distances beyond the horizon and may penetrate environments that could block radio waves with shorter wavelengths. whilst state-of-the-art most powerful VLF generation requires significant emitters, this antenna is simplest 4 inches tall, so it may potentially be used for duties that demand high mobility, along with rescue and defense missions.
“Our device is also masses of instances more efficient and can transmit facts quicker than previous devices of comparable size,” said SLAC’s Mark Kemp, the project’s most important investigator. “Its overall performance pushes the bounds of what is technologically possible and places portable VLF applications, like sending quick textual content messages in tough conditions, inside attain.”
The SLAC-led team mentioned their results nowadays in Nature Communications.
A enormous project
In modern-day telecommunications, radio waves delivery statistics thru air for radio broadcasts, radar and navigation systems and other applications. however shorter-wavelength radio waves have their limits: The sign they transmit becomes susceptible over very lengthy distances, can not journey thru water and is without problems blocked through layers of rock.
In assessment, the longer wavelength of VLF radiation lets in it to journey loads of toes through floor and water and hundreds of miles beyond the horizon thru air.
but, VLF technology also comes with principal challenges. An antenna is maximum green while its size is akin to the wavelength it emits; VLF’s lengthy wavelength calls for extensive antenna arrays that reach for miles. Smaller VLF transmitters are tons less green and can weigh masses of kilos, proscribing their intended use as cell devices. every other venture is the low bandwidth of VLF conversation, which limits the amount of information it can transmit.
the brand new antenna become designed with these problems in mind. Its compact length could make it feasible to build transmitters that weigh only some kilos. In tests that sent indicators from the transmitter to a receiver a hundred ft away, the researchers confirmed that their tool produced VLF radiation 300 instances greater efficiently than preceding compact antennas and transmitted data with almost a hundred times extra bandwidth.
“there are many thrilling potential packages for the era,” Kemp said. “Our device is optimized for lengthy-variety communication via air, and our research is calling on the fundamental science in the back of the method to discover approaches to similarly decorate its skills.”
A mechanical antenna
To generate VLF radiation, the tool exploits what’s known as the piezoelectric effect, which converts mechanical stress to a buildup of electrical rate.
The researchers used a rod-shaped crystal of a piezoelectric fabric, lithium niobate, as their antenna. when they carried out an oscillating electric powered voltage to the rod it vibrated, alternately shrinking and expanding, and this mechanical pressure brought about an oscillating electric contemporary whose electromagnetic strength then got emitted as VLF radiation.
the electrical cutting-edge stems from electric costs transferring up and down the rod. In conventional antennas, these motions are near the same size as the wavelength of the radiation they produce, and more compact designs typically require tuning devices large than the antenna itself. the new approach, on the other hand, “allows us to successfully excite electromagnetic waves with wavelengths which are a whole lot large than the motions along the crystal and without large tuners, which is why this antenna is so compact,” Kemp stated.
The researchers additionally determined a clever manner of tweaking the wavelength of the emitted radiation, he said: “We again and again transfer the wavelength during operation, which allows us to transmit with a big bandwidth. that is key to accomplishing records transfer rates of extra than one hundred bits in line with second — sufficient to ship a easy text.”