Science Daily April 12, 2019 The highest radiation efficiency antennas require size at the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. A team of researchers in the US (SLAC National Accelerator Laboratory, industry, SRI International) 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. Switching the wavelength during operation allowed them to transmit with a large bandwidth achieving […]
Tag Archives: Communication technology
Advancing undersea optical communications
MIT News August 17, 2018 The laser beams are hampered by significant absorption and scattering in the ocean. Researchers at MIT Lincoln Laboratory are applying narrow-beam laser technology, developed by the Laboratory for the LLCD (Lunar Laser Communication Demonstration), to enable communications between underwater vehicles. A beam from one underwater vehicle is pointed at the receive terminal of a second underwater vehicle. The position calculation is noise sensitive and can quickly accumulate errors of hundreds of meters when a vehicle is submerged for significant periods of time. To overcome this, they implemented an acquisition scanning function that is used to […]