A new type of pocket-sized antenna, developed at the Department of Energy’s SLAC National Accelerator Laboratory, could enable mobile communication in situations where conventional radios don’t work, such as under water, through the ground and over very long distances through air.
The device emits very low frequency (VLF) radiation with wavelengths of tens to hundreds of miles. These waves travel long distances beyond the horizon and can penetrate environments that would block radio waves with shorter wavelengths. While today’s most powerful VLF technology requires gigantic emitters, this antenna is only four inches tall, so it could potentially be used for tasks that demand high mobility, including rescue and defense missions.
“Our device is also hundreds of times more efficient and can transmit data faster than previous devices of comparable size,” said SLAC’s Mark Kemp, the project’s principal investigator. “Its performance pushes the limits of what’s technologically possible and puts portable VLF applications, like sending short text messages in challenging situations, within reach.”
The SLAC-led team reported their results today in Nature Communications.
A sizable challenge
In modern telecommunications, radio waves transport information through air for radio broadcasts, radar and navigation systems and other applications. But shorter-wavelength radio waves have their limits: The signal they transmit becomes weak over very long distances, can’t travel through water and is easily blocked by layers of rock.
In contrast, the longer wavelength of VLF radiation allows it to travel hundreds of feet through ground and water and thousands of miles beyond the horizon through air.
However, VLF technology also comes with major challenges. An antenna is most efficient when its size is comparable to the wavelength it emits; VLF’s long wavelength requires enormous antenna arrays that stretch for miles. Smaller VLF transmitters are much less efficient and can weigh hundreds of pounds, limiting their intended use as mobile devices. Another challenge is the low bandwidth of VLF communication, which limits the amount of data it can transmit.
The new antenna was designed with these issues in mind. Its compact size could make it possible to build transmitters that weigh only a few pounds. In tests that sent signals from the transmitter to a receiver 100 feet away, the researchers demonstrated that their device produced VLF radiation 300 times more efficiently than previous compact antennas and transmitted data with almost 100 times greater bandwidth.
“There are many exciting potential applications for the technology,” Kemp said. “Our device is optimized for long-range communication through air, and our research is looking at the fundamental science behind the method to find ways to further enhance its capabilities.”
A mechanical antenna
To generate VLF radiation, the device exploits what is known as the piezoelectric effect, which converts mechanical stress to a buildup of electrical charge.
The researchers used a rod-shaped crystal of a piezoelectric material, lithium niobate, as their antenna. When they applied an oscillating electric voltage to the rod it vibrated, alternately shrinking and expanding, and this mechanical stress triggered an oscillating electric current whose electromagnetic energy then got emitted as VLF radiation.
The electric current stems from electric charges moving up and down the rod. In conventional antennas, these motions are close to the same size as the wavelength of the radiation they produce, and more compact designs typically require tuning units that are larger than the antenna itself. The new approach, on the other hand, “allows us to efficiently excite electromagnetic waves with wavelengths that are much larger than the motions along the crystal and without large tuners, which is why this antenna is so compact,” Kemp said.
The researchers also found a clever way of tweaking the wavelength of the emitted radiation, he said: “We repeatedly switch the wavelength during operation, which allows us to transmit with a large bandwidth. This is key to achieving data transfer rates of more than 100 bits per second – enough to send a simple text.”
Learn and see more: SLAC develops novel compact antenna for communicating where radios fail
The Latest on: VLF radiation
via Google News
The Latest on: VLF radiation
- Air Force experimental satellite billed as the ‘largest unmanned structure in space’on July 23, 2019 at 5:00 pm
DSX can actively transmit VLF signals to study their influence on the electron population, he said. “This will allow a more thorough understanding of a key process governing the radiation environment.
- SpaceX Launches UML-built Instrument to Study ‘Killer Electrons’ in Spaceon June 28, 2019 at 10:43 am
“We expect that the transmitted VLF waves will interact with the killer electrons ... This will allow the satellite to fly through the inner and outer Van Allen radiation belts that surround Earth ...
- Science and Technology: An Ultra-Small Transmitter for VLF?on May 2, 2019 at 3:26 pm
"The device emits VLF radiation with wavelengths of tens to hundreds of miles. These waves travel long distances beyond the horizon and can penetrate environments that would block radio waves with ...
- Going where 5G can’t reach, this new antenna has serious potentialon April 12, 2019 at 8:27 am
It relies on VLF – or very low frequency – radiation, to deliver range that can be measured in thousands of miles, depending on the environment it’s being used in. VLF radio isn’t new, and its range ...
- SLAC develops novel compact antenna for communicating where radios failon April 12, 2019 at 7:17 am
pocket-sized antenna that emits very low frequency (VLF) radiation. April 12 is a little late for an April 1st article. Lithium niobate useful at micro and nanometer wavelengths isn't going to do much ...
- Principle of a New Compact Antenna (image)on April 12, 2019 at 4:02 am
This mechanical stress triggers an oscillating electric current (arrows) whose electromagnetic energy then gets emitted as VLF radiation (blue waves). The device can be switched during operations to ...
- A high Q piezoelectric resonator as a portable VLF transmitteron April 12, 2019 at 2:13 am
Very low frequency communication systems (3 kHz–30 kHz) enable applications not feasible at higher frequencies. However, the highest radiation efficiency antennas require size at the scale of the ...
- SLAC develops novel compact antenna for communicating where radios failon April 12, 2019 at 2:05 am
The device emits very low frequency (VLF) radiation with wavelengths of tens to hundreds of miles. These waves travel long distances beyond the horizon and can penetrate environments that would block ...
- SLAC develops novel compact antenna for communicating where radios failon April 12, 2019 at 2:03 am
In contrast, the longer wavelength of VLF radiation allows it to travel hundreds of feet through ground and water and thousands of miles beyond the horizon through air. However, VLF technology also ...
via Bing News